JPH02208827A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce variation in surface roughness of a protective film and to constantly control the surface by roughening the surface of a magnetic recording layer by dry etching in an inert gas atmosphere with applying DC bias voltage on the surface. CONSTITUTION:The magnetic recording layer with specified DC bias voltage applied is subjected to dry etching in an inert gas atmosphere to roughen the surface, on which the protective layer is formed by sputtering. Further, a liquid lubricant is applied thereon to a specified thickness to form the lubricating layer. By determining the proper DC bias voltage, the surface roughness of the carbon protective layer can be controlled to desired roughness. Thereby, the medium with excellent wear resistance can be constantly massproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a magnetic recording medium used in fixed magnetic disk drives and the like.

[Conventional technology]

In recent years, fixed magnetic disk drives have been widely used as external storage devices for information processing devices such as computers.
A magnetic recording medium (hereinafter also simply referred to as a medium) used in this device generally includes a non-magnetic substrate 1, for example, A1.
For example, on a base body with an N1-P layer formed on an alloy substrate,
A nonmagnetic metal thin film underlayer made of Cr, a ferromagnetic alloy thin film magnetic recording layer made of Co-Ni alloy, and a carbon thin film protective layer are sequentially formed by a continuous sputtering method, and then a lubricating layer made of a liquid lubricant is further formed on top of them. There are known configurations that have been formed. One of the characteristics required of such a medium is friction resistance when a magnetic head slides on the surface of the medium. It is known that the anti-friction properties of this medium depend on the surface roughness (microscopic shape of the surface) of the protective layer and the film thickness of the liquid lubricant forming the lubricating layer. In order to make the surface of the carbon protective layer have the required constant surface roughness and obtain a medium with good friction resistance properties with little variation, conventionally, the surface of the N1-P layer on the base was mirror-finished and then textured to obtain the desired surface roughness. A Cr underlayer, a Co-Ni alloy magnetic recording layer, and a carbon protective layer were sequentially laminated on top of the roughness, and the surface roughness of the carbon protective layer was adjusted to a certain level corresponding to the surface roughness of the N1-P layer of the substrate. A manufacturing method is adopted in which a lubricant layer is formed by roughening the surface and coating the surface with a liquid lubricant to a predetermined thickness.

[Problem to be solved by the invention]

However, in the conventional manufacturing method in which the surface roughness of the carbon protective layer is controlled by the surface roughness of the N1-P layer, which is the underlying layer, the intervening Cr layer.

Even if the Co-Ni alloy magnetic recording layer is a thin film, it is difficult to always form the surface of the carbon protective layer to the required constant surface roughness, resulting in variations in surface roughness and variations in the friction resistance properties of the medium. There was a problem that occurred.

This invention solves the above-mentioned problems, makes it possible to form a carbon protective layer with a required constant surface roughness on a magnetic recording layer with less variation, and mass-produces media with excellent friction resistance properties with less variation. The purpose is to provide a manufacturing method that can.

[Means for Solving the Problems] According to the present invention, the above object is to manufacture a magnetic recording medium in which a nonmagnetic metal underlayer, a magnetic recording layer, and a protective layer are sequentially formed on a nonmagnetic substrate by a sputtering method. According to the method, after forming a magnetic recording layer, a required DC bias voltage is applied to the substrate, the surface of the magnetic recording layer is dry-etched in an inert gas atmosphere, and then a protective layer is formed thereon. This is achieved by a manufacturing method that forms a protective layer with the desired surface roughness.

[Effect]

As mentioned above, the surface of the magnetic recording layer, which is the direct underlayer of the protective layer, is dry-etched in an inert gas atmosphere by applying the required DC bias voltage, and the protective layer is deposited thereon by sputtering. By doing this, the surface roughness of the protective layer becomes the required constant surface roughness with less variation compared to the conventional method of controlling the surface roughness of the substrate, and the liquid lubricant is applied on top of it to the required thickness. By forming a lubricating layer using the same method, it becomes possible to mass-produce a medium with uniform and excellent anti-friction characteristics with little variation.

〔Example〕

An N1-P alloy layer with a thickness of approximately 15 μm is formed by electroless plating on the surface of an A1 alloy disk substrate that has undergone internal and external diameter processing and surface cutting, and the surface is mirror-polished by 2 μm to 3 μm to improve the surface roughness. Line average roughness Ra: 10 to 20 people,
Ultra-precision cleaning is performed as it is without any texture processing, and it is used as a media base. Next, as shown in the partial plan view of FIG. 3, a pallet 1 made of a metal material 1, for example, an alloy plate
A plurality of substrates 2 treated as described above are set in the chamber, and this pallet is sent into the preparation chamber of an in-line sputtering film forming apparatus, and is evacuated to a vacuum of 5 Xl0-'Torr or less, so that the substrate temperature becomes 200°C. Heat as shown. Next, the pallet is transported to the film forming chamber, and A
Each layer constituting the medium is sequentially deposited on the substrate by sputtering while moving at low speed in an r gas atmosphere. Figure 4 is a longitudinal cross-sectional view of the main parts showing the state of the pallet moving inside the deposition chamber.
There is a rail 7 in the film forming chamber whose longitudinal direction is perpendicular to the plane of the paper.
A pallet 1 is held upright on wheels 4 that move on these rails 7 via an insulating plate 3 so that the surface of the substrate set thereon faces the film forming chamber wall 6. There is.

Reference numeral 5 denotes a copper plate electrode for applying a bias voltage to the substrate via the pallet 1. While moving the pallet 1 in this state, Cr was first applied as a base layer on the substrate at 1500 A in an Ar gas atmosphere at a pressure of 10 mTorr.
Co-Ni alloy was then deposited on top of the Co-Ni alloy to a thickness of
A film is formed to a thickness of 50 mm to form a magnetic recording layer.

Next, copper plate electrode 5. A DC bias voltage is applied to the substrate via the pallet 1 to dry-etch the surface of the magnetic recording layer. After the dry etching is completed, a carbon film is formed to a thickness of 400 mm on the surface of the magnetic recording layer to form a protective layer. After that, the pallet 1 is transported to the unloading chamber, the pallet is brought to atmospheric pressure, the pallet is taken out, the base is removed from the pallet,
A liquid lubricant is applied to the surface of the protective layer to form a lubricant layer with a thickness of about 20 mm, which is used as a medium.

In the above manufacturing method, the relationship between the DC bias voltage applied when dry etching the surface of the magnetic recording layer and the surface roughness of the carbon protective layer formed on the surface after dry etching was investigated, and the results are shown in Figure 1. The results shown in the diagram were obtained.

The surface roughness tplG-1 is an index of roughness used in the Abbott load curve, and is calculated by subtracting the cutting depth at a relative load length of 1% from the cutting depth at a relative load length of 10% in the Abbott load curve of the surface. It is shown as a value. It can be seen from FIG. 1 that the surface of the carbon protective layer can be made to have the required surface roughness by appropriately selecting the DC bias voltage.

Further, when the relationship between the DC bias voltage and the coefficient of dynamic friction of the obtained medium was investigated, the results shown in the diagram in FIG. 2 were obtained. These results are for a medium in which a liquid lubricant layer with a thickness of 18 mm was formed on the surface of the protective layer. In FIG. 2, 60 m1n for the dynamic friction coefficient μ indicates the dynamic friction coefficient after 0 minutes of sliding contact testing. From Figure 2, D
It can be seen that as the C bias voltage becomes negative and becomes larger, the dynamic friction coefficient decreases and the friction resistance of the medium improves, but it becomes almost constant above about 150 V.

From the above results, it is possible to manufacture a medium having the desired friction resistance by appropriately selecting the DC bias voltage applied when dry etching the surface of the magnetic recording layer.

In this example, dry etching was performed in a gas atmosphere of A, but it is not limited to Ar gas, and other inert gases may be used. Also, the heating temperature of the substrate was 130°C.
It is sufficient as long as it is within the range of ~270℃, and the gas pressure is also lOm
It is not limited to Torr.

〔Effect of the invention〕

According to this invention, the surface of the magnetic recording layer is dry-etched in an inert gas atmosphere by applying a DC bias voltage, and a protective layer is formed thereon. There is a close relationship between the DC bias voltage and the surface roughness of the protective layer, and by controlling the DC bias voltage, the surface roughness of the protective layer can be controlled using the conventional method of controlling the surface roughness of the substrate. It is possible to perform constant control with less variation compared to .

Therefore, by controlling this DC bias voltage to an appropriate required value and roughening the surface of the magnetic recording layer by dry etching, it is possible to form a protective layer with a desired constant surface roughness thereon without variation. By applying a liquid lubricant to a desired thickness on this protective layer to form a lubricating layer, it is possible to mass-produce a medium having a certain excellent anti-friction property with little variation. It is no longer necessary to texture the surface of the substrate as in the past.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the DC bias voltage applied during dry etching of the surface of the magnetic recording layer and the surface roughness of the protective layer, and Figure 2 is a diagram showing the DC bias voltage applied during dry etching of the surface of the magnetic recording layer. Figure 3 is a partial plan view of a pallet with substrates set, and Figure 4 is a vertical cross-sectional view of main parts showing the state of the pallet moving inside the film forming chamber. be. DC bias voltage (V) Figure 1 DC bias voltage (V) Figure Figure Figure

Claims (1)

[Claims] 1) In a method for manufacturing a magnetic recording medium in which a nonmagnetic metal underlayer, a magnetic recording layer, and a protective layer are sequentially formed on a nonmagnetic substrate by sputtering, the substrate is coated with a required DC after forming the magnetic recording layer.
The magnetic recording layer surface is dry-etched and roughened in an inert gas atmosphere by applying a bias voltage, and then a protective layer is formed thereon to form a protective layer with a desired surface roughness. A method for manufacturing a magnetic recording medium.