JP3139181B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium having excellent high density recording characteristics.

[0002]

2. Description of the Related Art Magnetic recording / reproducing apparatuses have been increasing in density year by year, and a magnetic recording medium having excellent short-wavelength recording / reproducing characteristics has been demanded. At present, a coating type magnetic recording medium in which a magnetic powder is coated on a substrate is mainly used, and the characteristics have been improved to satisfy the above-mentioned demands, but they have almost reached the limit.

[0003] Thin film magnetic recording media have been developed to exceed this limit. The thin-film magnetic recording medium is manufactured by a vacuum evaporation method, a sputtering method, a plating method, and the like.
Has excellent short-wavelength recording / reproducing characteristics. As the magnetic layer in the thin-film type magnetic recording medium, Co, Co-Ni, Co-
Ni-P, Co-O, Co-Ni-O, Co-Fe-
O, Co-Ni-Fe-O, Co-Cr, Co-Ni-
Cr and the like are being studied.

[0004] From the viewpoint of application to a magnetic tape, it is considered that a Co-O film or a Co-Ni-O film which is a partial oxide film is most suitable among these, and a Co-Ni-O film is considered. Has already been put to practical use as a Hi8 type VTR tape.

[0005] An example of a method for manufacturing a vapor deposition tape will be described below with reference to FIG. (FIG. 2) is an example of a configuration inside a vacuum evaporation apparatus for producing an evaporation tape. The substrate 1 made of a polymer film travels along the cylindrical can 2 in the direction of arrow 6. Evaporated atoms 9 evaporated from the evaporation source 8
Adhere to the substrate 1 to form a magnetic layer.

As the evaporation source 8, an electron beam evaporation source is suitable, in which a Co-based alloy as the evaporating substance 7 is filled. The reason why an electron beam evaporation source is used as the evaporation source is to evaporate a high melting point metal such as Co at a high evaporation rate. Reference numerals 3A and 3B denote shielding plates provided to prevent unnecessary evaporated atoms from adhering to the substrate. The former is a shielding plate for regulating a film formation start portion, and the latter is a shielding plate for regulating a film formation end portion. . In FIG. 2, each of the shielding plates has a single layer, that is, a single plate. Reference numeral 10 denotes an oxygen inlet for introducing oxygen into the vacuum chamber during vapor deposition. θ _i and θ _f are incident angles of the evaporated atoms 9 on the substrate 1 at the film formation start portion and the film formation end portion, respectively. The currently commercially available evaporated tape for Hi8 type VTR is manufactured by the above method. Reference numerals 4 and 5 denote a supply roll and a take-up roll of the substrate 1, respectively.

In the Co—O or Co—Ni—O magnetic layer thus manufactured, the axis of easy magnetization is inclined with respect to the normal to the film surface. That is, the axis of easy magnetization is not in the film plane or in the normal direction of the film surface, but in the normal plane including the incident direction of the evaporated atoms to the substrate, in the direction oblique to the normal line.

[0008] The recording / reproducing characteristics of the magnetic layer composed of the partial oxide film as described above greatly vary depending on the amount of oxygen introduced during vapor deposition and the method of introducing oxygen.

[0009]

In the future, demands for high output and high S / N in a short wavelength region will be further increased for magnetic tapes. As a method for meeting this demand, it is considered promising to improve the method of introducing oxygen into the magnetic layer made of a partial oxide film during the film formation.

[0010]

SUMMARY OF THE INVENTION The present invention fulfills the above-mentioned demands. In the present invention, an axis of easy magnetization is inclined on a substrate running along a cylindrical can with respect to a normal to a film surface. When forming a Co-based magnetic layer by a vacuum evaporation method,
The shielding plate that regulates the film formation end portion has a structure of two or more layers,
Further, oxygen is blown out toward the evaporated atoms from between the shielding plates and between the shielding plate and the cylindrical can.

[0011]

According to the method of the present invention, it is possible to optimize the oxygen concentration distribution in the thickness direction of the magnetic layer and to prevent the evaporation of evaporated atoms at the end of film formation. N can be provided.

[0012]

An embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of the inside of a vacuum deposition apparatus for carrying out the method of the present invention. Basically, it is the same as the conventional one shown in FIG. 2 (FIG. 2), except that a shielding plate for regulating the film formation end portion is different. In the present invention, the shielding plate that regulates the film formation end portion is double or more, and FIG. 1 is an example of the case of double. That is, as shown in FIG. 1, the shielding plate that regulates the film formation end portion is composed of 3B and 3B ′, and has a double structure. In addition, oxygen inlet 10
Are arranged as shown in FIG. 1, and the oxygen coming out therefrom passes between the shielding plates 3B and 3B ′ and between the shielding plate 3B ′ and the cylindrical can 2 toward the evaporated atoms 9. Blow out. It is desirable that the distance between the left end of the shielding plate 3B and the shielding plate 3B 'and the distance between the left end of the shielding plate 3B' and the cylindrical can be set to 2 cm or less. Further, oxygen needs to be blown out from between each shielding plate and between the shielding plate and the cylindrical can. Otherwise, the effects of the present invention will be significantly reduced. FIG. 1 shows an example in the case of double, but the same effect as in the case of double is obtained even in the case of triple or more. In addition, triple
In the above case, oxygen must be blown out from everything between the shielding plates.
There is no need, at least one between the shielding plates close to the cylindrical can
You just need to blow it out of the place. In FIG. 1, there is one oxygen inlet, but between the shielding plates 3B and 3B ′ and between the shielding plate 3B ′ and the cylindrical can 2, oxygen inlets are respectively arranged. Is also good.

With the above setting, the optimization of the oxygen concentration distribution in the thickness direction of the magnetic layer and the prevention of the wraparound of the evaporated atoms can be realized at the same time as compared with the evaporation tape manufactured by the conventional manufacturing method. Thus, a magnetic tape having a high reproduction output and a high S / N can be obtained.

The wraparound of the evaporated atoms will be described with reference to FIG. (Figure 2) shown in, evaporated atoms which is regulated by a shielding plate 3B for regulating the film forming completion portion, as shown in (FIG. 2), whether to adhere to the substrate as it incident angle of the rectilinear to theta _f In other words, there is no wraparound of the evaporated atoms. However, in practice, the evaporated atoms move mainly by diffusion, so that the evaporated atoms between the shielding plate 3B and the cylindrical can 2 spread to the right side as shown in FIG. 2.
This is called wraparound. If there is wraparound, evaporated atoms would adhere to the substrate at a small angle of incidence than theta _f. The evaporated atoms attached by such wraparound significantly deteriorate the recording / reproducing characteristics of the magnetic layer.

Next, the reason why a medium having a high reproduction output and a high S / N can be obtained with the structure of the present invention shown in FIG. 1 will be described in detail.

When a conventional vacuum vapor deposition apparatus having the structure shown in FIG. 2 is used to produce a vapor deposition tape composed of a Co-based magnetic layer, a shielding plate 3 for regulating the end of film formation in FIG. 2 is used.
A distance between the left end of B and the cylindrical can 2 (hereinafter, this distance is X
), The recording / reproducing characteristics change even if θ _f is set to be the same. When X is increased, the oxygen gas flows more easily, so that the amount of oxygen toward the evaporated atoms increases.
If the amount of oxygen going to the evaporated atoms simply increases,
An increase in reproduction output and a decrease in noise can be expected. However, when X is increased, the amount of wraparound of evaporated atoms increases. The wraparound reduces the reproduction output. Since the amount of decrease is greater than the increase in reproduction output due to an increase in the amount of oxygen, when X is increased, the reproduction output decreases. Therefore, if the amount of oxygen can be increased without increasing the wraparound, an increase in reproduction output and a decrease in noise can be expected.

When a double or more shield plate is used as in the present invention, the amount of oxygen toward the evaporated atoms can be increased without increasing the amount of evaporated atoms attached to the substrate due to wraparound. As a result, it is possible to increase the reproduction output and reduce noise.

Hereinafter, specific embodiments of the present invention will be described. First, an evaporation tape was produced using a vacuum evaporation apparatus having a basic configuration as shown in FIG. The diameter of the cylindrical can 2 was 1 m, and a polyethylene terephthalate film having a tape thickness of 10 μm was used as the substrate 1. Co was used as the evaporating substance 7. The distance between the left end of the shield plate 3B and the shield plate 3B 'and the distance between the left end of the shield plate 3B' and the cylindrical can 2 were set to 1 cm. Incident angle θ at the start of film formation
_i was set at 85 °, and the incident angle θ _{f at} the film formation end portion was set at 55 °.

With the above configuration, a magnetic layer having a thickness of 0.1 μm was formed at an average film deposition rate of 0.3 μm / s. In addition, 0.8 l /
Oxygen was introduced at a rate of min. The medium manufactured as described above is referred to as a sample (1).

For comparison, a plate for blocking the passage of oxygen is disposed between the shielding plates 3B and 3B ', so that oxygen is shielded from the shielding plate 3B.
A medium was produced by blowing out only from between B ′ and the cylindrical can 2 and the other conditions were the same as above. This is designated as sample (2). Further, a plate for blocking the passage of oxygen is disposed between the shielding plate 3B 'and the cylindrical can 2, and oxygen is blown only from between the shielding plates 3B and 3B'. Other conditions are the same as those described above. To produce a medium. This is designated as sample (3).

Further, for comparison, an evaporation tape was manufactured using a vacuum evaporation apparatus having a conventional basic structure as shown in FIG. 3B shielding plate that regulates the end of film formation
The film was formed under exactly the same conditions as described above, except that only one layer was used. However, the distance between the left end of the shielding plate 3B and the cylindrical can 2 was changed to produce three types of media. Samples (4) and 2 (2) were prepared by setting the distance to 1 cm.
The sample having a size of 4 cm was designated as sample (5), and the sample having a size of 4 cm was designated as sample (6).

Sample (1) prepared as described above
(6) was slit into a tape shape, and the recording / reproducing characteristics were evaluated using a ring-type magnetic head made of Sendust and having a gap length of 0.15 μm. At the time of this evaluation, a carbon protective layer having a thickness of 10 nm was formed on the surface of each sample. The evaluation results are shown in (Table 1).

[0023]

[Table 1]

Table 1 shows the reproduction output when recording and reproducing a signal having a wavelength of 0.5 μm and the noise at a frequency corresponding to a wavelength of 0.6 μm when recording and reproducing a signal having a wavelength of 0.5 μm. Assuming that the value of (1) is 0 dB, it is shown as a relative value to this.

From Table 1, it can be seen that all of the samples (4) to (6) produced by the conventional method had a lower reproduction output than the sample (1) obtained by the method of the present invention. As the distance between the left end of the shielding plate 3B in FIG. 2) and the cylindrical can 2 increases, the reproduction output decreases. This is thought to be due to the wraparound of the evaporated atoms. The noise of sample (4) was 1 dB higher than that of sample (1) obtained by the method of the present invention.
(6) is equivalent to (1).

As in the method of the present invention, the shielding plate is doubled, but a sample (2) produced by blowing oxygen only from between the shielding plate 3B 'and the cylindrical can 2; Sample (3) produced by blowing out only from between the plates
Are 1 dB lower in reproduction output and 1 dB higher in noise than (1).

As described above, the medium produced by the method of the present invention has the highest reproduction output and the lowest noise.

Although only an example of a Co partial oxide film has been described above, the same effect of the present invention can be obtained for a partial oxide film other than this composition. Further, as the substrate, a polyethylene terephthalate film has been described, but it goes without saying that the same applies to a polymer film such as a polyimide film, a polyamide film, a polyetherimide film, and a polyethylene naphthalate film. Further, the effect of the method of the present invention is the same as described above even when a polymer film having a nonmagnetic underlayer or a magnetic layer is used as a substrate. Further, the incident angles, θ _i , and θ _f of the evaporated atoms on the substrate are not limited to the values described above. However, in order to obtain a high reproduction output, it is necessary to satisfy the conditions of θ _i > θ _f and θ _f > 50 °. In the above, only the example in which the shield plate is double has been described, but the same effect can be obtained even if the shield plate is triple or more. However,
At this time, at least the side near the cylindrical can of the shielding plate
Oxygen from one location and between the shielding plate and the cylindrical can
It is necessary to blow out toward the evaporating atoms.

[0029]

According to the present invention, it is possible to provide a thin-film magnetic tape having a high reproduction output and a high S / N in a short wavelength region.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating the inside of a vacuum evaporation apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing the inside of a conventional vacuum deposition apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Cylindrical can 3A Shield plate for regulating film formation start part 3B, 3B 'Shield plate for regulating film formation end part 4 Supply roll 5 Winding roll 6 Substrate running direction 7 Evaporated substance 8 Evaporation source 9 Evaporated atom 10 Oxygen inlet

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuaki Ban 1006 Kazuma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-2-282479 (JP, A) JP-A-57- 198543 (JP, A) JP-A-4-216320 (JP, A) JP-A-4-222926 (JP, A) JP-A-63-310959 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/85

Claims (1)

(57) [Claims] 1. A substrate having an axis of easy magnetization inclined on a normal to a film surface on a substrate running along a cylindrical can.
When the o-based magnetic layer is formed by a vacuum deposition method, the shielding plate that regulates the film formation end portion has a double or more structure, and oxygen is interposed between the shielding plate and between the shielding plate and the cylindrical can. Is blown toward vaporized atoms.