JPH0668835B2 - Magnetic recording medium and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic disk and a magnetic tape, and a manufacturing method thereof.

B. 2. Description of the Related Art In a thin film magnetic recording medium, a technique of forming a carbon layer as a protective layer (or other intermediate layer) by a sputtering method is generally used. A carbon material target is used as the material.

Such a target is generally made of a carbon material having a maximum particle size exceeding 0.05 mm (however, 0.1 mm or less).

However, it has been found that the conventional target material has an excessively large maximum particle size, so that the discharge during film formation is unstable, the film formation rate is slow, and product deterioration and yield decrease occur.

C. OBJECT OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium which is stable and has good workability, and which has good performance such as durability, and a method for producing the same.

D. Structure of the invention and its action and effect That is, the present invention, the maximum particle size is 0.003mm ~ 0.05mm, the layer formed of a material consisting essentially of carbon, on the upper and / or lower side of the magnetic layer The present invention relates to a magnetic recording medium characterized by being provided.

In this magnetic recording medium, due to the presence of the above-mentioned substantially carbon layer (hereinafter, simply referred to as a carbon layer), the surface of the magnetic layer is protected, the adhesion to a support or the like and the film-forming property of the upper layer are improved. In addition to the above effect, the maximum particle diameter of the material for forming the carbon layer is made as small as 0.05 mm or less, so that the performance such as durability is greatly improved. The maximum particle diameter of the material for forming the carbon layer is preferably 0.02 mm or less.

On the other hand, the maximum particle size is preferably 0.003 mm or more in view of the cost of manufacturing the target and the yield. Further, this carbon layer may be formed as a protective layer 3 on the surface of the thin film magnetic layer 2 on the non-magnetic support 1 as shown in FIGS. 1 and 2, and further below the magnetic layer 2. It may be formed as the formation 4. In any case, the carbon layer is at least 1 on the support.
It can be provided as a layer, a protective layer having a layer thickness of 0.01 to 0.5 μm, or an underlayer. In the case of the underlayer, the film forming property of the upper layer can be well controlled, and the processing cost can be reduced because the support need not be processed so much in advance.

Here, as the support 1, it is possible to use Al, Al provided with an anodized film (for example, alumite treatment), Al subjected to Ni—P plating treatment, plastic such as polyimide, polyaramid, polycarbonate and the like. The support 1 may have various shapes such as a disk shape and a film shape. Further, as the above-mentioned magnetic layer 2, Co-Ni, Co-Ni-Fe, Co-Ni-C
Known thin film magnetic layers such as r, Co—Cr, γ-Fe ₂ O ₃ , and Ba ferrite can be used, and the layer thickness thereof may be 0.03 to 0.6 μm. The thickness of the magnetic layer is preferably 0.03 to 0.2 μm for in-plane recording, and 0.08 to 0.6 μm for vertical recording. The magnetic layer 2 can be formed by a known method such as a sputtering method or a vacuum deposition method.

Further, the present invention has a maximum particle size of 0.003 mm to 0.05 mm and performs sputtering by using a material substantially made of carbon as a target material, thereby forming a layer corresponding to the target material on the upper side of the magnetic layer and / or Alternatively, the present invention also provides a method for manufacturing a magnetic recording medium, which is characterized in that it is formed on the lower side.

That is, according to this manufacturing method, since a material having a maximum particle diameter of 0.05 mm or less and substantially consisting of carbon (hereinafter, simply referred to as a carbon material) is used as the target material,
By making the maximum particle size smaller than conventional products,
The discharge during sputtering becomes stable, and it is possible to improve the film forming speed and the yield. Carbon material used (target material)
Further, the maximum particle diameter of is preferably 0.02 mm or less.

In addition, in the present invention, the above-mentioned “maximum particle diameter” means the largest of the major axis diameters of particles measured by microscope observation.

Although the manufacturing method of the present invention is based on the sputtering method, it may be formed by the facing target sputtering method shown in FIG.

That is, in FIG. 3, 11 is a vacuum tank, 12 is an exhaust system including a vacuum pump for exhausting the vacuum tank 11, 13 is a predetermined gas introduced into the vacuum tank 11, and the gas pressure is 10 ^-1 to 10 -10. It is a gas introduction system set to about ^-4 Torr. The target electrode is configured as a counter target electrode in which a pair of targets T ₁ and T ₂ are spaced apart from each other by a target holder 14 and face each other in parallel. A magnetic field is formed between these targets by a magnetic field generating means (not shown).

In the sputtering apparatus configured as described above, a magnetic field is formed in a direction perpendicular to the surfaces of both targets T ₁ and T ₂ facing each other in parallel, and the magnetic field causes the cathode descending portion (that is, the target T ₁ -T ₂ Plasma atmosphere generated between and each target
In the region between T ₁ and T ₂ ) γ electrons emitted by the impact of the sputter gas ions accelerated by the electric field on the target surface are trapped in the space between the targets and moved toward the other facing target . The γ-electrons that have moved to the surface of the other target are reflected by the cathode fall portion in the vicinity thereof. Thus, the γ-electrons repeat the reciprocating motion while being bound by the magnetic field between the targets T _{1 and} T ₂ . During this reciprocating motion, the γ-electrons collide with the neutral atmospheric gas to generate ions and electrons of the atmospheric gas, and these products promote the emission of γ-electrons from the target and the ionization of the atmospheric gas. . Therefore, a high-density plasma is formed in the space between the targets T _{1 and} T ₂ , and along with this, the target material is sufficiently sputtered and deposited on the other substrate 1.

Compared to other flying means, this facing target sputtering apparatus is capable of forming a film at a high deposition rate by high-speed sputtering, does not directly expose the substrate to plasma, and can form a film at a low substrate temperature. It is advantageous because it is possible. Moreover, since the incident energy of the film material, which is flown by the facing target sputtering apparatus, to the substrate is smaller than that in the normal sputtering apparatus, the material is easily deposited in a desired direction with directionality. In addition, even if the film is formed by the magnetron sputtering method, the effect can be obtained without any change.

E. Examples Hereinafter, examples of the present invention will be described in detail.

Example 1 Target used Graphite target made by Poco (maximum particle size 0.05 mm) Ultimate vacuum 5 × 10 ^-6 Torr or less Ar gas pressure 3.0 × 10 ^-3 Torr Input power 3.5 W / cm ² Carbon layer thickness Under a sputtering condition of 0.03 μm or more, an attempt was made to form a carbon layer on a predetermined magnetic layer, such as a Co—Ni thin film recording magnetic layer, by sputtering. The results are shown in Table-1.

Table-1 Amount of abnormal discharge generated during film formation (excluding 60 minutes of preliminary discharge) Average 0.4 times / min Film formation speed 0.05 μm / min Protective film surface roughness Rz = 0.008 μm Protective layer durability after film formation Exam (CSS (contact Start and
Stop) test], there was no change after 10,000 times.

Comparative example Target material Comparative product Graphite target (maximum particle size 0.06mm) Ultimate vacuum 5 × 10 ^-6 Torr or less Ar gas pressure 3.0 × 10 ^-3 Torr Input power 3.5W / cm ² Carbon layer thickness 0.03μm or more Under the sputtering conditions, an attempt was made to form a carbon layer on the Co—Ni thin film recording magnetic layer by sputtering.

The results are shown in Table-2.

Table-2 Amount of abnormal discharge generated during film formation (excluding 60 minutes of preliminary discharge) Average 1.3 times / min Film formation speed 0.03 μm / min Protective film surface roughness Rz = 0.014 μm Protective layer durability after film formation Test (CSS test), 4000
After the passage of time, scratches were generated on the protective film due to the head running.

As is clear from the examples and comparative examples, in the example, although the film was formed under the same conditions as the comparative example, the abnormal discharge was reduced, the film forming speed was increased, and the protective film surface roughness was Diminished. As a result, durability was improved and satisfactory durability was obtained. The maximum particle size of the target is preferably 0.05 mm or less, and when a graphite target having a maximum particle size of 0.02 mm is used, more satisfactory durability is obtained, the number of abnormal discharge occurrences, the film forming speed, the surface roughness, etc. Was also the same.

Example 2 Target material used Graphite target manufactured by Poco (maximum particle size 0.02 mm) Ultimate vacuum degree of 5 × 10 ⁻⁶ Torr or less Ar gas pressure 3.0 × 10 ⁻³ Torr Input power 3.5 W / cm ² Carbon layer film An attempt was made to sputter deposit a carbon layer on a predetermined magnetic layer, such as a Co-Ni thin film recording magnetic layer, under a sputtering condition of a thickness of 0.03 μm or more. The results are shown below.

Occurrence of abnormal discharge 0.3 times / min Average film forming speed 0.05 μm / min Protective film surface roughness Rz = 0.008 μm After film formation, CSS test showed 10,000 times
There was no change.

Example 3 Target used Graphite target manufactured by Poco (maximum particle diameter 0.05 mm) Ultimate vacuum degree 5 × 10 ^-6 Torr or less Ar gas pressure 3.0 × 10 ^-3 Torr Sputtering conditions with input power 3.5 W / cm ² or more Under the above conditions, a magnetic disk having a layer structure as shown in FIG. 2 was manufactured. Here, the thickness of the underlying carbon layer is 0.1 μm, and the thickness of the protective layer is 0.03 μm.

As a result of a durability test (CSS test), there was no change after 10,000 times.

From the above results, the maximum particle size is the film forming process, film quality,
The effect on durability is large, and the maximum particle size of the target material and the maximum particle size of the obtained carbon layer are determined based on the present invention.
It can be seen that it is extremely important that the thickness is 0.05 mm or less.

[Brief description of drawings]

The drawings illustrate the present invention. FIGS. 1 and 2 are cross-sectional views of a magnetic recording medium, and FIG. 3 is a schematic cross-sectional view of a facing target sputtering apparatus. In the reference numerals shown in the drawings, 1 ... Nonmagnetic support 2 ... Magnetic layer 3 ... Carbon layer (protective layer) 4 ... Carbon layer (underlayer) 11 ... Vacuum chamber 12 ... Exhaust system 13 ... … Gas introduction system T ₁ , T ₂ …… Target.

Claims (2)

[Claims] 1. A maximum particle size of 0.003 mm to 0.05 mm,
A magnetic recording medium, wherein a layer formed of a material substantially made of carbon is provided on an upper side and / or a lower side of a magnetic layer. 2. The maximum particle size is 0.003 mm to 0.05 mm,
A method of manufacturing a magnetic recording medium, characterized in that a layer corresponding to the target material is formed on the upper side and / or the lower side of the magnetic layer by performing sputtering using a material substantially made of carbon as a target material.