JPH0740362B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a magnetic recording medium used in a magnetic recording apparatus.

[Prior Art and its Problems] In recent years, magnetic recording media such as magnetic disks used in magnetic recording devices have a tendency to have an ever-increasing recording density. About 1 μm
It is necessary to reduce the thickness to about 0.1 μm or less and to increase the coercive force (Hc). Therefore, as for the manufacturing method of the magnetic recording medium, the sputter method and the plating method, which can easily form a uniform thin film, are attracting attention instead of the spin coating method in which the film thickness of the magnetic layer is nonuniform in the submicron order. And formed as a magnetic layer by sputtering
Co-based alloys such as Co-Ni alloy magnetic thin films have come into use.

FIG. 2 shows a cross-sectional view of the essential parts of a disk-shaped magnetic recording medium. In FIG. 2, the magnetic recording medium comprises a non-magnetic substrate layer 2 coated on an alloy substrate 1, and a magnetic layer 4 coated on the non-magnetic substrate layer 2 via a non-magnetic metal underlayer 3. A protective lubricating film 5 is coated on the layer 4.

Aluminum alloy is often used for the alloy substrate 1 of the magnetic recording medium having the above-described structure, and is finished to have a predetermined surface roughness, parallelism and flatness. The non-magnetic substrate layer 2 is made of, for example, an electroless plated Ni-P alloy and has a predetermined hardness, and the surface is mirror-finished by mechanical polishing. The nonmagnetic metal underlayer 3 is generally formed of Cr by a sputtering method, and the magnetic layer 4 sputtered thereon is made of, for example, Co-30 at% Ni-7.5 at% Cr alloy.

The outline of the method of manufacturing the magnetic recording medium will be described below. Third
The figure is a schematic cross-sectional view for explaining the arrangement and operation of the members in the chamber of the sputtering apparatus. In FIG. 3, a vacuum exhaust port 7 and an Ar gas inlet port 8 are provided on the outer periphery of the chamber 6.
A tray 10 in which a vacuum exhaust system (not shown) and an Ar gas cylinder (both not shown) are connected to each other, both of which are provided with operation valves 9 and 9a, and inside the chamber 6 a substrate 1a is attached.
And a heater that faces the substrate 1a and heats the substrate 1a
11 is placed. The tray 10 can move in the direction of the arrow together with the substrate 1a, and the Cr target
The underlayer is sputtered by 12 and then Co-30at% Ni
A Co-based magnetic layer is sputtered from the magnetic alloy target 13 of −7.5 at% Cr.

First, for example, a disc-shaped aluminum alloy plate having a diameter of 3.5 inches is uniformly plated with Ni-P to a thickness of about 15 μm, and the surface of the disc is mirror-polished with a flat polish. After performing ultrasonic cleaning, steam cleaning, etc., the tray 10 in the chamber 6 is set. Next, the inside of the chamber 6 is exhausted from the exhaust port 7 to 5 ×
Evacuate to 10 ^-7 torr and use the heater 11 to move the substrate 1a to 10
While keeping the temperature at 0 ° C., the valve 9a is opened and Ar gas is introduced into the chamber 6 at a flow rate of 60 sccm from the Ar gas inlet 8 and the valve 9 is adjusted to adjust the pressure in the chamber 6 to 2 × 10.
Set to ^-2 torr. Next, sputtering power was applied to the Cr target 12 and the magnetic alloy target 13, and the tray 10 was transported in the direction of the arrow at a speed of 117 mm / min, so that the substrate 1
A Cr underlayer and a Co-30at% Ni-7.5% Cr magnetic layer are formed in this order on a.

Next, the relationship between the above process and the magnetic characteristics given to the obtained magnetic recording medium will be described. Magnetic property is retention (H
c), the product of the residual magnetic flux density (Br) and the film thickness of the magnetic layer (δ) (Br · δ), and the coercive force squareness ratio (S ^* ) are kept in good balance, and Hc750 (Oe), Br · δ350 ( G ・ μm), S ^*
It is desirable to set it to 0.80. To obtain these magnetic properties
Increasing Hc is given priority, and it is the film thickness of the Cr underlayer that contributes to the increase in Hc, and increasing the film thickness of the Cr underlayer tends to increase Hc. However, as the film thickness of the Cr underlayer increases, the magnetic anisotropy of Hc and S ^* becomes more prominent, and the reproduction output of the magnetic disk is modulated. Therefore, the Cr underlayer film thickness is 2000Å. Should be about. The thickness of the magnetic layer to be combined corresponding to the thickness of the Cr underlayer is best set to about 500Å.

From the above, in order to give optimum thicknesses to these underlayer and magnetic layer and maintain the magnetic characteristics in a well-balanced manner, in the manufacturing process of the magnetic recording medium, the power applied to each target that continuously sputters them It is urgently desired to determine the optimum density condition.

[Object of the Invention]

The present invention has been made in view of the above points, and an object thereof is to set an optimum power density range applied to an underlayer and a magnetic layer in order to obtain good magnetic characteristics when manufacturing a magnetic recording medium. To provide the value.

[Main points of the invention]

In the present invention, when the Cr underlayer of the magnetic recording medium and the Co-based alloy magnetic layer are continuously sputtered, the power densities applied to the Cr target and the Co-based alloy target are 1.49 to 17.9 (W /
By setting the cm ²⁾ and ^{0.43~5.17 (W / cm 2),} Hc750Oe as magnetic properties of the medium, Br · δ350
It is designed to satisfy G · μm, S ^* 0.80.

Example of Invention

 The present invention will be described below based on examples.

Since the device used in the present invention is the same as that shown in FIG. 3, its description is omitted. Target here
Using a Cr and Co-30 at% Ni-7.5 at% Cr alloy to manufacture a magnetic recording medium having the structure shown in FIG. 2 and setting other main film forming conditions exactly as described above. , Cr underlayer thickness is 2000Å, magnetic layer thickness is 500
It was carried out by selecting the tray transport speed so that it becomes Å and changing the sputter power density of each target. The combinations of the tray transport speed and the sputtering power density of each target are as shown in Table 1.

The magnetic characteristics of the medium at this time were measured with a sample vibration type magnetometer (VSM), the horizontal axis was the sputtering power density of the magnetic alloy target, and the vertical axes were Hc, Br · δ and S ^* , respectively ^.
When these values are plotted as, the diagram shown in FIG. 1 is obtained. It can be seen from FIG. 1 that the magnetic characteristics increase as the sputtering power density applied to the target increases and depend on the film forming rate per unit time. Hc750Oe, Br ・ δ350G ・ μm, S ^* 0.
The power density of the magnetic alloy target satisfying 8 is in the range of 0.43 to 5.17 W / cm ² from the result of FIG. 1, so the power density applied to the Cr target at this time is 1.49 to 1
It is 7.9 W / cm ² . The upper limit of the power density is set to 17.9 W / cm ² because if it is set higher than this, the temperature of the target rises excessively, which is not preferable for the sputtering apparatus.

〔The invention's effect〕

On the Ni-P plating layer coated on the substrate, Cr underlayer and Co
In the magnetic recording medium obtained by continuously sputtering the magnetic alloy layer, the coercive force of the magnetic properties, the residual magnetic flux density, and the squareness ratio could not be made sufficiently high values. The optimum sputter power density applied to the target and Co-based magnetic alloy target was 1.49 to 17.9, respectively.
W / cm ^2, in order to set the 0.43~5.17W / cm ^2, Hc750Oe, B
It is now possible to obtain a recording medium having excellent magnetic characteristics that satisfies r · δ350G · μm, S ^* 0.80, and it is possible to realize a high recording density.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the sputter power density applied to a magnetic alloy target and the magnetic characteristics of the medium, FIG. 2 is a sectional view of the structure of a magnetic recording medium, and FIG. 3 is a model sectional view of a sputtering chamber. 1, 1a: substrate, 3: underlayer, 4: magnetic layer, 6: chamber, 10: tray, 12: Cr target, 13: magnetic alloy target.

Claims (1)

[Claims] 1. A substrate whose main surface is plated with Ni-P is heated in a vacuum-exhausted chamber and then placed in the chamber.
After introducing Ar gas, Cr and Co based magnetic alloy targets are continuously sputtered to form Cr on the Ni-P plating layer.
In a method for manufacturing a magnetic recording medium in which an underlayer and a Co-based magnetic alloy layer are laminated in this order, the power density applied to the Cr target is 1.49 to 17.9 W / cm ² , and the power density applied to the Co-based magnetic alloy target is 0.43. ~ 5.17 W / cm ^{2 A} method for manufacturing a magnetic recording medium, characterized in that