JPH06111299A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium which can be repeatedly recorded at high density on a narrowed track with excellent S/N ratio by irradiating a magnetic film with carbon atoms to form a diamondlike hard carbon film adhering rigidly to a magnetic recording layer. CONSTITUTION:A raw fabric 6 having a magnetic thin film is generated on a polyester film by an electron beam depositing method. The magnetic film is irradiated with active carbon atoms from a carbon atom irradiating nozzle 10 while winding fabric 6 with a cooled rotary support 9. Thus, a diamondlike hard carbon film with carbon atoms is formed on the magnetic layer. Thus, the carbon film adhering rigidly to a magnetic recording layer is provided to obtain in a large quantity recording media which can be repeatedly recorded and reproduced at high density while holding the sliding surface of a head in an excellent state.

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.

[0002]

2. Description of the Related Art With the progress of information society, the amount of information to be recorded has remarkably increased, 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, Co-Ni-O
A magnetic recording medium having a ferromagnetic metal thin film represented by an obliquely evaporated film or a Co—O perpendicular magnetization film as a magnetic layer is promising.

A conventional magnetic recording medium will be described below. FIG. 3 shows an enlarged cross section of a conventional magnetic recording medium. In FIG. 3, 1 is polyethylene terephthalate,
Polymer film such as polyethylene naphthalate
_{2. In} many cases, a so-called fine particle coating layer in which inorganic ultrafine particles such as ZnO or organic ultrafine particles such as imide are dispersed and applied is used. 2 is a ferromagnetic metal thin film of a single layer or a multilayer structure of Co—Ni—O formed by oblique vapor deposition with a continuously changing incident angle, a perpendicular magnetization film by gradient vapor deposition of Co—Cr, Co—O, etc. A magnetic layer, 3 is a protective film such as a diamond-like hard carbon film, 4 is a lubricating layer such as fatty acid and fluorine oil, and 5 is a back coat layer having good smoothness, which is often seen in thin magnetic tapes. In the magnetic recording medium having the above-described structure, the magnetic layer is formed by moving along a rotating can or a rotating belt in a separate process in a solution coating method to form a fine particle coating layer on a polymer film in an oxygen atmosphere. In many cases, Co, Co-Ni, etc. are deposited by electron beam evaporation at a certain incident angle. The hard carbon film is mainly used actively in the disk-shaped medium, and there are few concrete application examples to the magnetic tape, but in manufacturing, the technology disclosed in the magnetic tape and the magnetic disk is disclosed. Can be applied as is or with a slight modification. Film formation by plasma CVD method (for example, JP-A-61-54036), electron beam evaporation method (for example, JP-A-61-224140), sputtering method (for example, JP-A-62-2644)
No. 32) Cluster Ion Vapor Deposition Method (for example, Japanese Patent Laid-Open Publication No.
Film formation according to JP-A-4-33722) has been studied. What they have in common is that they raise the energy of carbon ions and electrons to some extent.

The magnetic recording medium having the above structure is
Due to the hardness of the diamond-like hard carbon film and the frictional characteristics with its counterpart, it is possible to withstand repeated sliding between the magnetic head and the tape at a high relative speed. If it is still insufficient, further improve the adhesiveness with the ferromagnetic metal thin film,
S to improve still durability as a video tape
Amorphous carbon film disposed through an iO ₂ film (JP-A-61-242323) Amorphous carbon film disposed through an organic plasma polymerized film (JP-A-62-167616) One in which a carbon film is arranged through a film (Japanese Patent Laid-Open No. 64-79932) is proposed.

[0005]

However, in the above conventional structure, the durability becomes insufficient as the carbon film becomes thinner, and the phenomenon becomes more remarkable as the thickness of the magnetic recording medium becomes thinner. In particular, in order to improve the recording density by narrowing the track, a magnetic recording medium with high output and good durability is required. Even if the carbon film is thickened to improve the durability, S /
There is a problem that the density is insufficient because the N ratio is lowered.

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

[0007]

In order to achieve this object, a method of manufacturing a magnetic recording medium according to the present invention is to form a diamond-like hard carbon film on a magnetic thin film with carbon atoms.

[0008]

With this structure, the magnetic layer is firmly adhered to the carbon, and the mechanical properties of the carbon film itself are not only hard but also microscopically excellent in uniformity. A thin magnetic recording medium having both durability and a high S / N ratio can be reproducibly manufactured.

[0009]

【Example】

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

In FIG. 1, reference numeral 6 is a raw material for forming a protective film, in which a magnetic thin film is formed as a recording layer by an electron beam evaporation method on a polyester film (including one having a surface treatment to give fine irregularities). The recording layer may be any of oblique magnetization, perpendicular magnetization, a laminated body of both. Reference numeral 7 is a feed-out shaft for the original fabric, and 8 is a take-up shaft for the original fabric with a protective film formed thereon. Although this figure shows the main configuration of the apparatus for the purpose of forming only the protective film, it goes without saying that the lubricating layer may be formed in vacuum immediately after forming the protective film.
Reference numeral 9 denotes a rotary support, which preferably has a structure capable of cooling. Reference numeral 10 is a carbon atom irradiation nozzle, which extracts carbon ions from hydrocarbon plasma or arc discharge between carbon electrodes, neutralizes them with an electron shower, separates them with charged particles and a magnetic field, and activates active carbon atoms on the magnetic thin film surface. It may be configured to be directed, but it goes without saying that it is not limited to this.

In order to further clarify the effect of this embodiment, a magnetic recording medium will be concretely manufactured as a prototype, and the results of characteristics comparison with those obtained by the conventional method will be described in detail.

The thickness is 6.8 μm, the Young's modulus is 540 and 590 [Kg / mm ² ] in the longitudinal and width directions, 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. Two types of magnetic layers were prepared: a so-called perpendicular magnetization film (type a) obtained with a component having an incident angle of 40 to 12 degrees and a so-called oblique vapor deposition film (type b) obtained with a component having an incident angle of 90 to 35 degrees. . On the magnetic layer, a diamond-like hard carbon film was formed with carbon atoms at a rate of 15 Å / sec to 70 Å and a diamond-like hard carbon film was formed on the magnetic layer to be 120 Å. As a conventional example, 120 Å and 120 Å diamond-like carbon films were prepared by a plasma CDV method in which methane gas was ionized by high frequency discharge to form a carbon film. Perfluoropolyether as a lubricant was further placed on each carbon film by a 40 Å solution coating method to form a back coat layer of 0.45 μm, and an 8 mm wide magnetic tape was experimentally manufactured to compare the characteristics. To compare the characteristics of each magnetic tape, a recording wavelength of 0.47 was obtained by modifying a high-band 8 mm video deck.
.mu.m and track pitch 9 .mu.m were used for relative comparison of S / N ratio. The length of the magnetic tape is 100m, and it is 5 randomly.
A roll was selected and displayed as an average value of 5 rolls. The still characteristics were compared at 40 ° C. and 5% RH by increasing the tension to 25 g. 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. Is obtained.

As described above, according to the manufacturing method of this embodiment,
By forming a diamond-like hard carbon film with carbon atoms on a magnetic thin film, it is possible to obtain a large number of magnetic recording media that can stably maintain excellent S / N ratio even in repeated use in a narrow track and high density recording with good reproducibility. be able to.

(Second Embodiment) A second 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 second embodiment of the present invention. In FIG. 2, the same components as those in FIG. 1 are given the same numbers. An apparatus in which hydrogen atom irradiation nozzles having the same structure as the carbon atom irradiation nozzles are arranged adjacent to each other may be used. Figure 2
11 is a carbon atom irradiation nozzle and 12 is a hydrogen atom irradiation nozzle. It is preferable that the irradiation area is basically configured such that the irradiation area of hydrogen atoms is the same as or wider than the irradiation area of carbon atoms.

In order to further clarify the effect of this embodiment, a magnetic recording medium will be concretely manufactured as a prototype, and the results of characteristics comparison with those obtained by the conventional method will be described in detail.

With a thickness of 6.8 μm, Young's modulus of 540 and 590 [Kg / mm ² ] in the longitudinal and width directions, respectively, and an average roughness of 3
0Å polyethylene terephthalate film (diameter 15
O ₂ ultrafine particles of SiO ₂ with an average density of 20 particles / μm ² were fixed on the resin was used in advance.) Was wound up along a rotary can cooled to 20 ° C. with a diameter of 1 m to collect oxygen. Then, Co was electron beam evaporated to form a magnetic layer of 0.18 μm. As the type of the magnetic layer, a so-called perpendicular magnetization film obtained with a component having an incident angle of 40 to 12 degrees was used. A diamond-like hard carbon film of 70Å was formed on the magnetic layer by carbon atoms and hydrogen atoms.

Carbon atoms were formed by irradiation at 2 × 10 ¹⁸ atoms / cm ² and hydrogen atoms at 7 × 10 ¹⁶ atoms / cm ² (tape 2a), carbon atoms at 6 × 10 ¹⁸ atoms / cm ² , hydrogen. Atoms were formed by irradiation with 4 × 10 ¹⁶ atoms / cm ² (Tape 2
b), carbon atoms 6 × 10 ¹⁷ atoms / cm ² , hydrogen atoms 4
× 10 ¹⁶ atoms / cm ² , formed by irradiation (Tape 2c)
It carried out on 3 conditions of.

As a conventional example, 120 Å and 220 Å of diamond-like carbon film were prepared by 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 each of the carbon films by a 40 Å solution coating method to form a back coat layer of 0.45 μm, and an 8 mm wide magnetic tape was manufactured as a prototype and the characteristics were compared. To compare the characteristics of each magnetic tape, modify the high-band 8mm VCR
Digital recording was performed with a μ track and a bit length of 0.2 μ, and relative error rates were compared. Durability is 5 ℃,
The error rate was evaluated after adding a 200-pass history at 80% 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 according to the present example has an excellent effect that high-density digital recording can be performed with a good error rate under a narrow track condition.

As described above, according to this embodiment, by forming a diamond-like hard carbon film on the magnetic film by carbon atoms and hydrogen atoms, the bond strength between the carbon film and the magnetic film is further strengthened by hydrogen bonding. Even in a small area, crystals with a diamond structure occupy a lot, and even if it is made thin, it has an excellent protective effect, maintains a stable S / N ratio, and has a good error rate in digital recording in narrow tracks. A magnetic recording medium which can be obtained by repeated use can be manufactured.

(Third Embodiment) A third embodiment of the present invention will be described below. The apparatus for manufacturing a magnetic recording medium used to carry out the method for manufacturing a magnetic recording medium of the third embodiment of the present invention is basically the one shown in FIG. 2, and has the same structure as the carbon atom irradiation nozzle. A device in which the nitrogen atom irradiation nozzles are arranged adjacent to each other may be used.

It is preferable that the irradiation area of the nitrogen atom is basically the same as or wider than the irradiation area of the carbon atom.

The atomic ratio of carbon to nitrogen is such that nitrogen is 0.
Since the range of 5 to 4% is preferable, it is desirable to carry out in that range. This is because if it is 0.5% or less, the improvement effect described later is small, and if it is 4% or more, foreign matter adheres to the head, which is presumed to be due to the film becoming brittle.

In order to further clarify the effect of this embodiment, a magnetic recording medium will be concretely produced as a prototype and the results of characteristics comparison with those obtained by the conventional method will be described in detail.

With a thickness of 5.5 μm, Young's moduli of 940 and 990 [Kg / mm ² ] in the longitudinal and width directions, respectively, and an average roughness of 3
A 0 Å aramid film (using a coating layer of 150 Å diameter SiO ₂ ultrafine particles having an average density of 20 particles / μm ² fixed on the resin in advance) at 20 ° C.
Oxygen was introduced while winding along the cooled rotating can, and Co was electron beam evaporated to form a magnetic layer of 0.18 μm.
Formed. As the type of the magnetic layer, a so-called perpendicular magnetization film obtained with a component having an incident angle of 40 to 12 degrees was used. A diamond-like hard carbon film of 70Å was formed on the magnetic layer by carbon atoms and nitrogen atoms.

It was formed by irradiating carbon atoms at 2 × 10 ¹⁹ atoms / cm ² and hydrogen atoms at 1.6 × 10 ¹⁷ atoms / cm ² (tape 3a), and carbon atoms at 6 × 10 ¹⁸ atoms / cm ^2. Formed by irradiating nitrogen atoms at 9 × 10 ¹⁶ atoms / cm ² (tape 3b), irradiating carbon atoms at 6 × 10 ¹⁷ atoms / cm ² , and hydrogen atoms at 2 × 10 ¹⁶ atoms / cm ² . Formed (tape 3
It carried out on 3 conditions of c).

As a conventional example, 120 Å and 220 Å diamond-like carbon films were prepared 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 each of the carbon films by a 40 Å solution coating method to form a back coat layer of 0.45 μm, and an 8 mm wide magnetic tape was manufactured as a prototype and the characteristics were compared. To compare the characteristics of each magnetic tape, modify the high-band 8mm VCR
Digital recording was performed with a μ track and a bit length of 0.2 μ, and relative error rates were compared. Durability is also 45
The error rate was evaluated after adding 130 pass histories at 10 ° C and 10% 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 3).

[0033]

[Table 3]

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

As described above, according to this embodiment, the diamond-like hard carbon film is formed on the magnetic film by the carbon atoms and the nitrogen atoms, so that the adhesion strength between the carbon film and the magnetic film is strengthened, and even the minute portion is uniform. Thus, even if there are few crystals having a diamond structure, the hardness can be obtained, and even if it is made thin, it has an excellent protective effect, maintains a stable S / N ratio, and has a good error rate in digital recording in a narrow track. It becomes possible to manufacture a magnetic recording medium which can be obtained by repeatedly using.

As described above, in the first to third embodiments, the examples using the magnetic tape have been described in detail. However, the same effect can be obtained for a magnetic disk or an optical disk requiring a protective film. . Although the diamond-like hard carbon film was formed directly on the magnetic thin film, it may be combined with a known pretreatment such as plasma polymerization.

[0037]

As described above, according to the present invention, by forming a diamond-like hard carbon film with carbon atoms on a magnetic film, an excellent S / N ratio can be repeatedly used in high density recording with a narrow track. It is possible to obtain a large number of magnetic recording media which can be stably held with good reproducibility.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part of a magnetic recording medium manufacturing apparatus used in a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of an essential part of a magnetic recording medium manufacturing apparatus used in a second embodiment of the present invention.

FIG. 3 is an enlarged sectional view of a conventional magnetic recording medium.

[Explanation of symbols]

 6 Raw fabric 10, 11 Carbon atom irradiation nozzle 12 Hydrogen atom irradiation nozzle

Claims (3)

[Claims] 1. A method of manufacturing a magnetic recording medium, comprising forming a diamond-like hard carbon film with carbon atoms on a magnetic thin film. 2. A method of manufacturing a magnetic recording medium, wherein a diamond-like hard carbon film is formed on a magnetic thin film by carbon atoms and hydrogen atoms. 3. A method of manufacturing a magnetic recording medium, wherein a diamond-like hard carbon film is formed on a magnetic thin film by carbon atoms and nitrogen atoms.