JPH08102054A - Method and apparatus for manufacturing magnetic recording medium - Google Patents

Abstract

(57) [Summary] [Constitution] After the inside of the chamber 21 is made into a predetermined vacuum atmosphere by a vacuum source, the unwinding roll 24 causes the base film 23 to run onto the cooling can roll 22. The ferromagnetic material in the crucible 26 is irradiated with an electron beam from the electron gun 27 to melt and evaporate, and oblique vapor deposition is performed on the base film 23 in the presence of oxygen supplied from the nozzle 29. Then, by implanting oxygen ions from the ECR type ion gun 30, an oxide layer is formed with a uniform depth on the surface of the magnetic layer. The obtained processed film is wound on a winding roll 25. [Effect] The oxide layer on the surface of the vapor-deposited magnetic layer of the magnetic recording medium can be formed more densely and with a uniform and controlled depth. This reduces spacing loss, reduces noise, and improves the C / N ratio.

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 and a method for manufacturing the same, and more particularly to a vapor deposition type magnetic recording medium having excellent magnetic characteristics and a method for manufacturing the same.

[0002]

2. Description of the Related Art A vapor deposition type magnetic recording medium has a large saturation magnetization as compared with a coating type magnetic recording medium and the like and is suitable for high density recording and is used in various fields of application. The vapor-deposited magnetic recording medium is generally manufactured by vapor-depositing a ferromagnetic material in a vacuum atmosphere on a base film such as PET to form a magnetic layer. In this case, it has been found that the coercive force and saturation magnetic flux density required for the magnetic layer can be improved by performing vapor deposition while introducing oxygen. For example, as shown in FIG. 3, according to a conventional manufacturing method, a base running on the cooling can roll 4 from the unwinding roll 2 to the winding roll 3 in a vacuum chamber 1 connected to a vacuum source (not shown). A magnetic metal in the crucible 6, for example, cobalt is deposited on the film 5 by electron beam irradiation from the electron gun 7. At that time, oxygen is introduced from the nozzle 8 to the vicinity of the vapor incidence region. In addition, what is shown by 9 is a shielding plate, which is designed to limit the incident angle of the vapor in an oblique direction.

FIG. 4 schematically shows a sectional view of the conventional magnetic recording medium 10 thus obtained. The magnetic layer 12 deposited on the base film 11 has a column structure, and an oxide layer 13 is formed between columns. It is considered that the oxide layer improves the coercive force and the saturation magnetic flux density of the magnetic layer. Further, since the nozzle 8 is opened in the vicinity of the cooling can roll 4, an oxide film 14 is also formed on the surface of the magnetic layer 12, which serves as a protective layer for protecting the inside of the magnetic layer and improving corrosion resistance. Is playing.

[0004]

Although there are some advantages in forming a film while introducing oxygen in this way, on the other hand, the atomic magnetic metal vapor evaporated by the electron beam is extremely small. Since it is highly reactive, it requires delicate control and has a problem of poor operability. Further, the oxide layer between the columns is necessary for improving the coercive force and the saturation magnetic flux density, but if the oxide layer on the surface of the magnetic layer becomes excessively thick, spacing loss due to the film thickness will occur, and C / N There was also a problem that the magnetic characteristics such as the ratio deteriorate.

[0005]

According to the present invention, a magnetic material is deposited on a base film while introducing oxygen gas in a vacuum chamber to form a magnetic layer, and then the surface of the magnetic layer is oxidized by ion implantation. A method of making a magnetic recording medium is provided that comprises forming a layer. Thus, by separately forming the oxide layer on the surface of the magnetic layer by implanting oxygen ions, the amount of oxygen can be accurately controlled and the depth of the oxide layer formed on the surface of the magnetic layer can be made uniform. be able to. Therefore, a dense oxide layer can be formed thinner than before. Therefore, the protective layer can be formed thinner, and the thinner layer can improve the corrosion resistance as in the conventional case, while reducing the spacing loss due to the film thickness and improving the magnetic characteristics. .

According to the present invention, there is also provided a manufacturing apparatus suitable for carrying out the above method, which comprises a vacuum chamber, a cooling can roll provided in the vacuum chamber,
Means for running the base film on the cooling can roll, evaporation source of magnetic material provided below the cooling can roll, electron gun for irradiating the evaporation source with an electron beam, evaporation source and the cooling can roll Between the cooling can roll and the shielding plate for limiting the incident range of vapor from the evaporation source to the cooling can roll, a nozzle for supplying oxygen gas in a direction away from the cooling can roll, and a base film And ion implantation means arranged toward the cooling can roll on the downstream side of the nozzle when viewed in the traveling direction of.

In the present invention, an oxide layer is formed on the surface of the deposited magnetic layer by ion implantation. Ion implantation is performed by an ion implanter, which generally consists of an ion source, a mass separator, and an implantation chamber. When the accelerating voltage is high, the latter stage accelerating tube is used,
A beam scanner is used when beam scanning is required. Preferably, the ion implantation means is an ECR type ion gun. In the present invention, the ECR type ion gun uses microwave discharge in a magnetic field to implant O ⁺ ions into the surface of the magnetic layer formed on the base film in the present invention. In the present invention, generally, the acceleration voltage is 0.5 to 80 kV and the driving current is 10 to 200 mA. The ion implanting means is not limited to the microwave ion source, and a Freeman type ion source or the like may be used.

In the present invention, the magnetic material forming the magnetic layer formed by vapor deposition is a ferromagnetic metal material used in the manufacture of ordinary metal thin film type magnetic recording media. For example
Ferromagnetic metals such as Co, Ni, Fe, Fe-Co, Fe-Ni, Co-N
i, Fe-Co-Ni, Fe-Fh, Fe-Cu, Co-Cu, Co-Au, Co
-Y, Co-La, Co-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-
Cu, Mn-Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni-C
Ferromagnetic alloys such as r, Fe-Co-Cr, and Ni-Co-Cr can be mentioned. As the magnetic layer, a thin film of iron or a thin film of a ferromagnetic alloy containing iron as a main component is preferable, and at least one selected from a ferromagnetic alloy containing iron, cobalt, nickel as a main component and nitrides or carbides thereof is preferable. . The thickness of the magnetic layer is generally about 100 to 3000 angstroms.

For high-density recording, it is preferable to use so-called oblique vapor deposition, in which the vapor incidence range is limited to an oblique direction by a shielding plate. The degree of vacuum during vapor deposition is 10 ^-4 to 10 ^-7
It is about Torr. The magnetic layer formed by vapor deposition may have either a single-layer structure or a multi-layer structure. In the present invention, a magnetic layer is vapor-deposited while introducing oxygen through a nozzle, and desired magnetic characteristics, that is, coercive force and saturation magnetic flux density are given to the magnetic layer. In this case, the nozzle introduces oxygen away from the cooling can roll so that no surface oxide layer forms. The oxygen flow rate is generally 5-200 SCCM, preferably 15-80 SCCM.

In the present invention, polyethylene terephthalate is generally suitable as the base film.
However, it is also possible to use polyesters such as polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polycarbonate, polyvinyl chloride, polyimide and aromatic polyamide. it can. The thickness of these supports is about 2 to 50 μm.

The magnetic recording medium obtained by the present invention may have a back coat layer, a lubricating layer and the like depending on the application and as required.

[0012]

1 shows an example of a manufacturing apparatus 20 according to the invention, which is suitable for carrying out the manufacturing method according to the invention. This is a vacuum source (not shown), for example, a vacuum chamber 21 connected to a vacuum pump, a cooling can roll 22 provided in the vacuum chamber 21, and a base film 23 such as a PET film running on the cooling can roll 22. And a take-up roll 25 and a take-up roll 25. A crucible 26 is disposed below the cooling can roll 22 as an evaporation source, and a ferromagnetic material such as cobalt is contained in the crucible 26. An electron gun 27 is disposed on the side wall of the vacuum chamber 21, and the crucible 26 is irradiated with an electron beam to evaporate the ferromagnetic material in the crucible 26. Between the crucible 26 and the cooling can roll 22, a shield plate 28 for limiting the incident range of the vapor of the ferromagnetic material vaporized by the electron beam from the crucible 26 to the cooling can roll 22 in an oblique direction is arranged. There is. A nozzle 29 for supplying oxygen gas is arranged between the cooling can roll 22 and the shield plate 28.
The tip of 29 is bent obliquely downward so as to supply oxygen gas in a direction away from the cooling can roll 22. An ECR type ion gun 30 is arranged as an ion implantation means on the downstream side of the nozzle 29 when viewed in the traveling direction of the base film 23.

In order to manufacture a magnetic recording medium according to the present invention, the inside of the chamber 21 is made into a predetermined vacuum atmosphere by a vacuum source, and then the base film 23 is run from the unwinding roll 24 on the cooling can roll 22. Electron gun 27 to crucible 26
The ferromagnetic material inside is irradiated with an electron beam to melt and evaporate, and oblique vapor deposition is performed on the base film 23. This is performed in the presence of oxygen supplied from the nozzle 29. Then, oxygen ions are implanted into the surface of the magnetic layer from the ECR type ion gun 30 to form an oxide layer on the surface with a uniform depth. The treated film thus obtained was taken up by the take-up roll 25.
Wound up. After that, slitting, winding, cassette mounting etc. are performed by general methods,
Commercialized as 8 mm video and video tape.

A schematic sectional view of a magnetic recording medium obtained by the method of the present invention is shown in FIG. As shown in the figure, this magnetic recording medium 40 comprises a base film 41 and a column-structured magnetic layer 42 formed by vapor deposition on the base film 41. The columns are separated by an oxide layer 43, and also the magnetic layer
The surface of 42 is partially oxidized to form an oxide layer 44. Also in FIG. 4 shown above, the oxide layer 14 is formed on the surface of the magnetic layer.
2 is formed, the oxide layer 44 on the surface of the magnetic recording medium according to the present invention of FIG. 2 is more dense and can have the same protective function as the oxide layer 14 with a thinner thickness. Therefore, the spacing loss due to the film thickness can be reduced, which leads to the improvement of the magnetic characteristics. Further, according to the present invention, since the depth of the oxide layer can be uniformly controlled by ion implantation, noise can be reduced and a magnetic recording medium having a high C / N ratio can be obtained.

Example 1 Using the apparatus shown in FIG. 1, the vacuum chamber 21 was evacuated to 10 ^-6 Torr, and then an electron beam was applied to the cobalt metal in the crucible 26 at 60 keV by an electron gun 27 to form a vapor deposition atmosphere. did. A PET film having a thickness of 6 μm was run on the cooling can roll 22 at a speed of 2 m / s, and a magnetic layer was formed by oblique vapor deposition at a thickness of 1800 Å. At this time, oxygen gas was introduced from the nozzle 29 at 75 SCCM. Next, oxygen ions were implanted from the ECR type ion gun 30 at an acceleration voltage of 60 kV and an implantation current of 55 mA. Next, on the side opposite to the magnetic layer, a back coat paint containing carbon black and a binder resin was applied onto the PET film to form a back coat layer having a thickness of 0.5 μm. The obtained product was cut into a width of 8 mm and loaded into a cassette to prepare an 8 mm video cassette.

Example 2 A magnetic layer and an oxide film were formed under the same conditions as in Example 1 except that the accelerating voltage from the ion gun 30 was set to 40 kV, and then the same treatment was carried out to produce an 8 mm video cassette.

Comparative Example Using the apparatus shown in FIG. 3, the vacuum chamber 1 was evacuated to 10 ^-6 Torr, and then the electron beam was applied to the cobalt metal in the crucible 6 at 30 keV by the electron gun 7 to form a vapor deposition atmosphere. . A PET film having a thickness of 6 μm was run on the cooling can roll 4 at a speed of 2 m / s, and a magnetic layer was formed by oblique vapor deposition at a thickness of 1800 Å. At this time, oxygen gas was introduced from the nozzle 8 at 120 SCCM. After that, a back coat layer was formed in the same manner as in Example 1, cut,
It was loaded to make an 8 mm video cassette.

The outputs of the 8 mm video cassettes obtained in the examples and comparative examples were measured at recording wavelengths of 1 MHz, 3 MHz and 7 MHz by using a commercially available VTR deck modified device. The results are shown in Table 1. In Table 1, the output is a relative value based on the comparative example. Also, as a corrosion resistance test,
The Bs retention rates after storage for 4 weeks at 60 ° C. and 90% relative humidity were compared. Furthermore, the C / N ratio was also compared.

[0019]

[Table 1]

[0020]

As described above, according to the present invention, the oxide layer on the surface of the magnetic layer of the vapor deposition type magnetic recording medium can be formed more densely and with a uniform and controlled depth.
As a result, spacing loss is reduced, noise is reduced, and reproduction output and C / N ratio are improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a manufacturing apparatus of the present invention.

FIG. 2 is a schematic sectional view of a magnetic recording medium of the present invention.

FIG. 3 is a schematic view showing an example of a manufacturing process of a vapor-deposited magnetic recording medium according to a conventional technique.

FIG. 4 is a schematic cross-sectional view of a conventional magnetic recording medium.

[Explanation of symbols]

 20 Evaporation device 21 Vacuum chamber 22 Cooling can roll 23 Base film 24 Unwinding roll 25 Winding roll 26 Crucible 27 Electron gun 28 Shielding plate 29 Nozzle 30 ECR type ion gun

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohide Mizunoya 2606 Akabane, Kaigamachi, Haga-gun, Tochigi Prefecture Kao Corporation Information Science Research Institute (72) Inventor Akira Shiga 2606 Akabane, Kaiga-cho, Haga-gun, Tochigi Prefecture Hana Information Science Laboratory, Wang Co., Ltd.

Claims (3)

[Claims] 1. A magnetic material comprising depositing a magnetic material on a base film while introducing oxygen gas in a vacuum chamber to form a magnetic layer, and then forming an oxide layer on the surface of the magnetic layer by ion implantation. Recording medium manufacturing method. 2. A vacuum chamber, a cooling can roll provided in the vacuum chamber, means for running a base film on the cooling can roll, and evaporation of a magnetic material provided below the cooling can roll. Source, an electron gun for irradiating the evaporation source with an electron beam, and a shield plate arranged between the evaporation source and the cooling can roll for limiting an incident range of vapor from the evaporation source to the cooling can roll. A nozzle arranged between the cooling can roll and the shielding plate for supplying oxygen gas in a direction away from the cooling can roll, and directed toward the cooling can roll on the downstream side of the nozzle when viewed in the traveling direction of the base film. Apparatus for manufacturing a magnetic recording medium, which is composed of ion implantation means arranged in parallel. 3. The manufacturing apparatus according to claim 2, wherein the ion implanting means is an ECR type ion gun.