JPS6161445B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a magnetic recording medium suitable for high-density recording. In recent years, there has been a growing demand for magnetic recording media with higher recording densities, and metal thin film types in which a ferromagnetic thin film is formed on a nonmagnetic substrate by vapor deposition, sputtering, magnetron high speed sputtering, ion plating, electroplating, electroless plating, etc. Development of magnetic recording media is actively underway. In the case of such metal thin film magnetic recording media, in order to obtain high coercive force, which is an essential condition for increasing recording density, it is necessary to impart magnetic anisotropy to the ferromagnetic thin film by some means. The technology for imparting such magnetic anisotropy is to obliquely inject a vapor flow of a ferromagnetic material such as Fe, Co, Ni, or an alloy thereof in a vacuum onto a substrate such as a polyester film. A so-called oblique vapor deposition method is known, which is disclosed in Japanese Patent Publication No. 19389/1989, etc., in which the film is deposited while the film is being deposited. According to such an oblique vapor deposition method, vapor anisotropy is imparted to the ferromagnetic thin film, resulting in increased coercive force, improved adhesion of the deposited thin film, and even higher output in the short wavelength region. This will improve the results. However, on the other hand, the deposition rate of the thin film is slow, and the deposition efficiency is poor relative to the amount of evaporation of the ferromagnetic material, resulting in extremely low manufacturing efficiency.Furthermore, the output power can only be improved in the short wavelength region, so electromagnetic The disadvantage is that the conversion efficiency and the linearity of the maximum output frequency characteristics are unfavorable. The present invention has been made to eliminate these drawbacks of the conventional oblique vapor deposition method, and provides a method with high holding power, high adhesion strength of the thin film, and effective film formation speed and deposition efficiency. The main objective is to provide a method for manufacturing a high-output magnetic recording medium with excellent linearity, which increases manufacturing efficiency, and also achieves improved output in the long wavelength region in addition to high output in the short wavelength region. shall be. The inventor of the present invention has made the present invention as a result of extensive studies regarding such an objective. That is, in the case of forming a ferromagnetic thin film on a substrate by obliquely injecting a vapor flow of a ferromagnetic material onto the substrate while moving a non-magnetic substrate in vacuum, the vapor flow follows the transfer of the substrate. The purpose is to gradually change the angle between the flow and the normal to the substrate from a low angle to a high angle. The present invention will be explained below with reference to the embodiment shown in FIG. The ferromagnetic thin film in the present invention is formed by vacuum evaporation, and any known vacuum evaporation technique such as evaporation, sputtering, ion plating, etc. may be used. Therefore, the manufacturing method of the present invention is carried out in a predetermined vacuum, and the apparatus used is housed in the vacuum chamber 1. As shown in FIG. 1, the vacuum chamber 1 is configured to be maintained at a predetermined vacuum by an evacuation device 2 consisting of, for example, a rotary pump and a diffusion pump.
A means for introducing an inert gas or the like into the tank is provided. A steam generator 3 is disposed within such a vacuum chamber 1. The steam generator 3 may be of any known heating method such as a resistance heating method, an electron beam heating method, or a high frequency induction heating method, and its structure, material,
The dimensions, shape, etc. can be arbitrarily determined as appropriate. On the other hand, a ferromagnetic material 4 is stored in the steam generator 3, and is evaporated by heating by the steam generator.
The vapor flow is configured to be generated. In this case, a known ferromagnetic material may be used as the ferromagnetic material, such as Fe, Co, Ni, an alloy thereof, a mixture thereof with other additive elements, or an oxide thereof, etc. Both can be used. On the other hand, in the vacuum chamber 1, the non-magnetic substrate 5 is usually moved above the steam generator 3. In this case, a film-like continuous body is generally used as the nonmagnetic substrate 5, and at this time, the substrate 5 is continuously conveyed and transferred at a predetermined speed. Such continuous conveyance is normally carried out by winding the substrate wound around a supply reel 6 onto a take-up reel 7 according to a known method, as shown in FIG. I am going to do it,
Generally, between the supply reel 6 and the take-up reel 7,
The base body 5 is conveyed substantially diagonally upward above the steam generator 3. Furthermore, as the material of the non-magnetic substrate 5, any known substrate material can be used, such as organic polymer materials such as polyester and polyimide, and non-magnetic metal materials such as aluminum and zinc. Prior to the deposition of the thin film, they may be subjected to various base surface treatments, base film formation, back surface treatments, etc., if necessary. Note that the base 5
The thickness etc. can be selected from a wide range, and the conveying speed may generally be about 0.1 to 10 m/min. In the present invention, under a configuration similar to that in the conventional oblique evaporation method, the angle between the vapor flow and the normal line of the substrate (incident angle) changes to a low angle as the substrate 5 is transferred. The angle changes gradually from high to high. In order to configure this, it is normal to use a film-like continuous body as the base 5 and to convey it continuously. The substrate is arranged so that two or more straight surfaces are formed on the base body that moves along this traveling guide, and the steam inflow angle to these multiple straight surfaces (the angle between the normal to the straight surface and the steam flow) is ) may be made to increase discontinuously and stepwise from a low angle to a high angle. In this case, the steam flow, ignoring its surroundings, is
It can be thought of as a straight line extending radially from the center of the evaporation surface of the ferromagnetic material 4 in the steam generator 3, and the normal to the straight line is strictly speaking the above-mentioned line when the roundabout of the steam flow is ignored. Although this is a normal line drawn to the center of the effective adhesion area on a straight plane, the base body 5 is normally moved almost obliquely upward within the effective adhesion area above the steam generator 3. At that time, the angle that each linear plane formed by the traveling guide makes with the vertical line is gradually reduced. Although various guiding methods are possible as the traveling guide, it is common to use commonly used guide rolls and guide the base 5 from the back surface thereof. Furthermore, if this guide position is made variable, the above-mentioned incident angle can be changed in various ways, and the desired characteristics of the magnetic recording medium to be obtained can be appropriately realized. A preferred example of such a case is shown in FIG. In FIG. 1, three running guides 81, 82, 83 are provided between the supply reel 6 and the take-up roll 7.
are arranged, and the angles θ ₁ , θ ₂ , θ 3 made by the three straight planes formed between each guide 81, 82, 83 and the winding roll 7 with the vertical line are θ ₁ > θ ₂ > _{θ 3 .} The base body 5 is configured to move in the direction of arrow P along each guide 81, 82, 83. In such cases, the number of running guides, the number of linear surfaces formed by them, the length of each linear surface, etc. can be changed in various ways, and the size of the angle that each linear surface makes with the vertical line can be changed. The degree of change of each angle can also be changed as long as the final straight line is approximately within a range of 10 to 40 degrees from the perpendicular line, and these can be determined as appropriate based on the ferromagnetic material used and the required magnetic property values, etc. good. In such a configuration, if the substrate is transferred as described above and the ferromagnetic material is deposited according to a conventional method, a layered structure in which a ferromagnetic thin film is formed on one surface of the substrate can be continuously manufactured. become. The layered body formed in this way functions as a magnetic recording medium by itself, but if necessary, the upper surface of the thin film and the back surface of the substrate may be subjected to prescribed processing, then cut, and used for various magnetic tapes, etc. It is considered as a magnetic recording medium. In the present invention, deposition is carried out in such a way that the angle between the vapor flow and the normal to the substrate changes stepwise from a low angle to a high angle as the substrate moves, so that the resulting ferromagnetic thin film is It has a relatively low coercive force at the bottom and a relatively high coercive force at the top. For this reason,
The thin film as a whole has a high coercive force,
In addition to improving the output in the short wavelength region, which is a feature of the oblique evaporation method, it also improves the output in the long wavelength region, resulting in high output and good frequency characteristics. In addition, the adhesion strength is comparable to that of the conventional oblique evaporation method, and the film formation speed and deposition efficiency are higher than those obtained by the conventional oblique evaporation method, which achieves almost the same coercive force.
This has been greatly improved, and the manufacturing efficiency is extremely good. The inventor conducted various experiments to confirm the effects of the present invention. An example is shown below. Experimental Example The effects of the present invention were confirmed using the apparatus shown in FIG. A polyethylene terephthalate film with a thickness of 6 μm was used as the substrate 5, and the conveyance speed was approximately 1 m/min. Also, the angles θ ₁ , θ ₂ , θ ₃ between each straight line and the vertical line are θ ₁ = 55°, θ ₂ =
40°, θ ₃ =25°, and the length of each straight line surface was made equal. On the other hand, as a ferromagnetic material, 80wt% Co and
Using an alloy consisting of 20wt% Ni, this was made into a 40mm
A tungsten wire is wound inside a φ aluminum crucible, and the winding is housed in a resistance-heating type steam generator 3 consisting of an aluminum container with a capacity of 20 c.c. Through an alternating current of 20×
It was evaporated in vacuum chamber 1 at 10 ^-6 Torr. On the other hand, for comparison, according to the conventional oblique evaporation method,
Vapor deposition was carried out under the same conditions as above, without using the running guides 82 and 83, but with the straight plane formed by the guide 81 and the take-up roll 7 making an angle of 60° with the vertical line. Table 1 shows the film formation speed and magnetic properties of the obtained thin films when the above two methods were followed. Note that the deposition efficiency was increased by about 30% in the case of the present invention compared to the case of the conventional oblique vapor deposition method.

[Table] In addition, the layered structure obtained by both of the above methods was cut,
After creating an open tape, its electromagnetic conversion efficiency and maximum output (MOL) frequency characteristics were measured.
The electromagnetic conversion efficiency is shown in Figure 2, and the MOL is shown in Figure 3. In both figures, curve a is the case according to the present invention, curve c is the case according to the conventional oblique evaporation method, and curve b is the commercially available γ-
These are the results for Fe ₂ O ₃ coated tape. From both figures, the frequency characteristics of the present invention are about 10 dB higher in the high range compared to the γ-Fe ₂ O ₃ tape, and about 10 dB higher in the low range than in the case of the conventional oblique evaporation method, and the frequency characteristics are improved. You can see that From these results, it is believed that the above-mentioned effects brought about by the present invention are obvious.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention, and FIGS. 2 and 3 show electromagnetic conversion characteristics and maximum output frequency characteristics, respectively, for explaining the effects of the present invention. It is a line diagram. 4...Ferromagnetic material, 5...Nonmagnetic substrate.

Claims (1)

[Claims] 1. A method for producing a magnetic recording medium in which a vapor flow of a ferromagnetic material is obliquely incident on a non-magnetic substrate while moving the substrate in a vacuum to form a ferromagnetic thin film on the substrate. A method for manufacturing a magnetic recording medium, characterized in that the angle between the vapor flow and the normal to the substrate is changed stepwise from a low angle to a high angle according to the transition.