JPH0341896B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a ferromagnetic metal thin film type magnetic recording medium that has excellent electromagnetic conversion characteristics and improved uniformity. Conventional magnetic recording media have γ-
It has been manufactured by coating and drying a magnetic powder, typically Fe ₂ O ₃ , dispersed in an organic binder. In recent years, in order to improve recording density, a method of manufacturing a magnetic recording medium by forming a ferromagnetic metal thin film by vacuum deposition, sputtering, plating, etc. has been attracting attention, and efforts are being made to put it into practical use. In particular, a method using vacuum evaporation has the advantage that it does not require drainage treatment as in the case of plating, the manufacturing process is simple, and the deposition rate is high. In order to improve the adhesion between the deposited film and the base material or to improve the electromagnetic conversion characteristics, the metal vapor flow evaporated from the evaporation source crucible is ionized by high frequency waves or thermoelectrons, and the ionized vapor flow is introduced into the base material. A method has been proposed in which a thin film is formed towards the target.
However, although some of the conventional methods have been put into practical use, they are insufficient for the purpose of forming a uniform film in the width direction of a web-like base material such as a magnetic tape. Therefore, the present inventors have conducted intensive research on a method for forming stable films by ionizing a metal vapor flow using high frequency waves, with the aim of improving the electromagnetic conversion characteristics by improving the shortcomings of upper air.As a result, the present inventors have developed the present invention. This is what we discovered. That is, the method of manufacturing a magnetic recording medium according to the present invention is to install a plasma generating coil near an evaporation source, and to set the coil so that the central axis of the coil is substantially parallel to the width direction of the web-like substrate. In this method, a magnetic recording medium is manufactured by applying high-frequency power to a magnetic field, generating plasma, and forming a magnetic film by vapor deposition in the plasma. Furthermore, by providing an electrode that applies a negative voltage to the evaporation source on the base material or near the base material and the evaporation source, thereby accelerating the ionized vapor flow,
A magnetic thin film with better properties can be obtained. In the present invention, in order to increase the coercive force of the magnetic recording medium, the ionized vapor flow may be obliquely incident on the base material. Further, in the present invention, in order to incorporate oxygen into the magnetic thin film, a method of forming the film in an oxidizing atmosphere is also used. As the evaporation source heating method, any method such as a resistance heating method, a laser beam heating method, a high frequency heating method, an electron beam heating method, etc. can be used. Electron guns used in the electron beam heating method include transverse electron guns and self-accelerating (pierce) electron guns, but the piercing type is advantageous for evaporating large amounts of magnetic material on a manufacturing scale. be. When manufacturing a magnetic recording medium by the vacuum evaporation method of the present invention, the ferromagnetic metal used to form the magnetic thin film may be metals such as Fe, Co, or Ni, or Fe-
Co, Fe−Ni, Co−Ni, Fe−Co−Ni, Fe−Rb,
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-
Ferromagnetic alloys such as Cr, Ni-Cr, Fe-Co-Cr, Fe-Co-Ni-Cr, etc. are used. The thickness of the magnetic film is generally 0.05 μm to 1.0 μm, preferably 0.1 μm to 0.4 μm, since it needs to be thick enough to provide sufficient output as a magnetic recording medium and thin enough to perform high-density recording. It is. Flexible substrates include polyethylene terephthalate, polyimide,
Plastic bases such as polyamide, polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate, or Al,
Metal strips such as Al alloy, Ti, Ti alloy, and stainless steel are used. FIG. 1 shows an example of a vacuum evaporation apparatus for producing magnetic recording media, which is equipped with a conventional high frequency application mechanism. The inside of the vacuum container 1 is divided into an upper chamber (not shown) and a lower chamber, and a cooling can 2 is installed between the upper chamber and the lower chamber. The web-like base material 5 is transported along the cooling can 2 from the upper chamber to the lower chamber where vapor deposition is performed, and then transferred to the upper chamber again. An evaporation source crucible 4 of magnetic material is arranged below the cooling can 2, and the evaporated vapor from the evaporation source 4 is obliquely evaporated onto a tape-shaped substrate 5 moving along the cooling can 2 through a mask 3. It's getting old. The magnetic material in the evaporation source crucible 4 is heated by the electron beam 12 irradiated from the electron gun 6 . A coil 10 for applying high frequency is installed between the cooling can 2 and the evaporation source 4, and is connected to a high frequency power source 8 via a matching box 7. The vacuum container 1 is provided with a gas introduction part 9 so that a desired gas can be introduced into the lower chamber. 2 and 3 show an example of a vacuum evaporation apparatus for magnetic recording media based on the method of manufacturing magnetic recording media according to the present invention. As shown in FIG. 1, a cooling can 22, a mask 23, an evaporation source crucible 24, a web-like base material 25, and an electron gun 26 are provided in the vacuum container 21, and as attached mechanisms, a matching box 27 and a high-frequency power source are provided. 28, gas introduction part 29
is installed. The plasma generating coil 30 for high frequency application in this device is arranged so that its central axis 33 is substantially parallel to the width direction of the web-like base material 25. Furthermore, an electrode 31 that can apply a negative DC voltage to the evaporation source 24 is provided near the cooling can 22 . Next, the present invention will be explained with reference to Examples, but the present invention is not limited thereto. Example 1 A magnetic tape was produced by forming a cobalt magnetic film on a polyethylene terephthalate base having a thickness of 15 μm using the winding type vapor deposition apparatus shown in FIGS. 1 and 2. Oxygen gas is introduced into the vacuum chamber from the gas introduction parts 9 and 29, and the pressure inside the vacuum chamber is 1×10 ^-4 Torr.
The flow rate was adjusted so that A high frequency of 600 W (13.56 MHz) is applied to the coils 10 and 30 to generate plasma in the vacuum chamber. The acceleration electrode 31 has -
A DC voltage of 1kV is applied. An original magnetic tape was prepared by setting the oblique entrance angle regulated by the masks 3 and 23 to 50°, and performing evaporation so that the thickness of the cobalt magnetic evaporated film was 1200 Å. We measured the film thickness unevenness in the width direction of the fabricated tape, the 6MHz video signal output on a VHS type VTR of the tape slit to 1/2 inch width, and the bulk noise of the tape, and the results are shown in the table below. As is clear from this, the magnetic tape manufactured by the method of the present invention is excellent in film thickness uniformity in the width direction, video output, and noise.

[Table] Example 2 Similar to Example 1, Co-Ni alloy (Ni/Ni/
5wt%) was vapor-deposited to a thickness of 1500Å to produce a magnetic tape material. During vapor deposition, a gas containing a mixture of oxygen and argon at a ratio of 5:2 is introduced into the vicinity of the vapor deposition area through the introduction ports 9 and 29, and a vacuum level of 1.4 x 10 ^-4 Torr is created using masks 3 and 2.
The oblique incidence angle regulated to 3 was set to 45°. The characteristics of the magnetic tape produced by applying 1 KW of high frequency power were measured in the same manner as in Example 1, and the results shown in the table below were obtained.

[Table] As is clear from the table, the magnetic tape manufactured by the manufacturing method of the present invention is excellent in film thickness uniformity in the width direction, video output, and noise. As is clear from the examples, the method of manufacturing a magnetic recording medium by plasma deposition in which the central axis of the high-frequency coil is installed parallel to the width direction of the moving web-like substrate is as follows. A magnetic tape with excellent film thickness uniformity, improved video output, and reduced noise can be obtained, and is of great value in manufacturing vapor-deposited magnetic tapes.

[Brief explanation of drawings]

FIG. 1 shows an example of a vacuum evaporation apparatus for manufacturing magnetic recording media equipped with a conventional high-frequency application mechanism, and FIGS. 2 and 3 show vacuum evaporation equipment for manufacturing magnetic recording media based on the present invention. This shows an embodiment of the invention. 22 is a cooling can, 23 is a mask, 24 is an evaporation source crucible, 25 is a web-shaped base material,
26 is an electron gun, and 30 is a plasma generating coil.

Claims (1)

[Claims] 1. In a method of manufacturing a magnetic recording medium by heating and evaporating a magnetic metal or alloy to form a deposited magnetic thin film on a moving web-shaped inorganic or organic polymer substrate, plasma is placed near the evaporation source. A generating coil is installed, and the central axis of the coil is made substantially parallel to the width direction of the web-like substrate, and high-frequency power is applied to the coil to generate plasma, which is then deposited. A method of manufacturing a magnetic recording medium, characterized in that: 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the magnetic thin film is formed by directing the vapor flow of the magnetic metal or alloy obliquely to the base material. 3. The method of manufacturing a magnetic recording medium according to claim 1, further comprising introducing an oxidizing gas into the vacuum chamber in which the magnetic thin film is formed. 4. The magnetic recording medium according to claim 1, wherein a negative potential is applied to the base material or an electrode provided in the vicinity thereof with respect to a crucible containing the magnetic metal or alloy. Production method.