JPS6379234A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent magnetic characteristics by confining the range of the power density to be impressed to a Cr target and Co magnetic alloy target at the time of executing continuous sputtering to laminate and form an underlying layer and magnetic layer on a substrate. CONSTITUTION:The substrate 1a which is the aluminum alloy formed by Ni-P plating and polishing to a specular surface is set on a tray 10 and the inside of a chamber 6 is evacuated to 5X10<-7>Torr through a discharge port 7, then the substrate 1a is heated to 100 deg.C by a heater 11. Gaseous Ar is admitted through a gas introducing port 8 into the chamber 6 and the pressure in the chamber is set at 2X10<-2>Torr by a valve 9. The Cr underlying layer and Co alloy magnetic layer are successively formed on the substrate 1a when the tray is moved after 1.49-17.9W/cm<2> power density is applied to the Cr target and 0.43-5.17W/cm<2> power density to a Co magnetic alloy target, respectively. The magnetic recording medium having the excellent magnetic characteristics is thus manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method of manufacturing a magnetic recording medium used in a magnetic recording device.

[Prior art and its problems]

In recent years, magnetic recording media such as magnetic disks used in magnetic recording devices have tended to have higher and higher recording densities.
There is a need to increase the holding force (Hc) even further as the thickness decreases to 0.1 μm or less. For this reason, sputtering and plating methods, which can easily form a uniform thin film, are attracting attention as a manufacturing method for magnetic recording media, as they can easily form a uniform thin film, instead of the spin code method, which results in non-uniform magnetic layer thickness on the submicron order. At the same time, magnetic thin films of Co-based alloys, such as Co--Ni alloys, formed by sputtering have come to be used as magnetic layers.

FIG. 2 shows a sectional view of the main part of the disk-shaped magnetic recording medium. In FIG. 2, the magnetic recording medium has a non-magnetic base layer 2 coated on an alloy substrate 1, and a magnetic layer 4 is further coated on this non-magnetic base layer 2 via a non-magnetic metal underlayer 3. The layer 4 is coated with a protective lubricant film 5.

Aluminum alloy is often used for the alloy substrate 1 of the magnetic recording medium configured as described above, and is finished to a predetermined surface roughness, parallelism, and flatness.

The nonmagnetic base layer 2 is made of, for example, a Ni--P alloy electrolessly plated to have a predetermined hardness, and the surface is mechanically polished to a mirror finish. The non-magnetic metal underlayer 3 is generally formed by sputtering using Cr, and the magnetic layer 4 sputtered thereon is made of, for example, Co-30at.
%Ni-7.5at%Cr alloy is used.

An outline of the method for manufacturing this magnetic recording medium will be described below. Third
The figure is a schematic cross-sectional view for explaining the arrangement and operation of members inside a chamber in a sputtering device. In FIG. 3, a vacuum exhaust lower and an Ar gas inlet 8 are provided on the outer periphery of the chamber 6, and these communicate with a vacuum exhaust system and an Ar gas cylinder (not shown), both of which are equipped with operation valves 9 and 9a, and the chamber 6 A tray 10 on which the substrate 1a is attached is disposed inside the tray 10, and the tray 10 is placed opposite the substrate 1a.
A heater 11 is placed to raise the temperature. The tray 10 can move in the direction of the arrow together with the substrate 1a, and in the process of movement, the base layer is sputtered by the Cr target 12, and then Co-30a, Ni-7,5at%
A Co-based magnetic layer is formed by sputtering from a Cr magnetic alloy target 13 .

First, for example, Ni-P plating is uniformly applied to a thickness of about 15 μm on a disc-shaped aluminum alloy plate with a diameter of 3.5 inches.
This is subjected to surface mirror finishing by plane polishing, and then subjected to ultrasonic cleaning with an alcohol solution, ultrasonic cleaning with a fluorocarbon solution, steam cleaning, etc., and then set on a tray 10 in the chamber 6.

Next, move inside chamber 6 from the exhaust lower to 5X10”
The substrate 1a is heated and maintained at 100° C. using the heater 11, and the valve 9a is opened to allow Ar gas to flow into the chamber 6 from the Ar gas inlet 8 at a flow rate of 60 SCCm, and the valve 9 is adjusted. and set the pressure inside chamber 6 to 2×10-torr. Then C
Apply sputtering power to the r target 12 and the magnetic alloy target 13, and move the tray 10 in the direction of the arrow at 117tx.
By conveying at a speed of /m, a Cr underlayer and a Co-30at%Ni-7.5%Cr magnetic layer are formed in this order on the substrate la.

Next, the relationship between the above process and the magnetic properties imparted to the obtained magnetic recording medium will be described. The magnetic property is the coercive force (Hc
), the product of the residual magnetic flux density (Br) and the magnetic layer thickness (δ) (Br-8), and the coercive force squareness ratio (S*) are maintained in a well-balanced manner, Hc>750 (Oe), Br-a >350(G
It is desirable that the magnetic properties are as follows: m), s ”〉o, s o. To obtain these magnetic properties, priority should be given to increasing Ha, and the film thickness of the Cr underlayer contributes to increasing Hc. However, as the thickness of the Cr underlayer increases, Hc tends to increase. However, as the thickness of the Cr underlayer increases, the magnetic anisotropy of Hc and S* becomes more pronounced.
Since modulation of the reproduction output of the magnetic disk occurs, the thickness of the Cr underlayer should be approximately 2000X. It is best to set the thickness of the magnetic layer to be about 5,001 mm corresponding to the thickness of the Cr underlayer.

From the above, in order to give the underlayer and magnetic layer an optimal film thickness and maintain well-balanced magnetic properties, it is necessary to apply the power density to each target for continuous sputtering during the manufacturing process of magnetic recording media. It is urgently desired to determine the optimal conditions for

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to set the optimum power density range to be applied to the underlayer and magnetic layer in order to obtain good magnetic properties when manufacturing a magnetic recording medium. It's about providing value.

[Key points of the invention]

In the present invention, when forming the Cr underlayer and the Co-based alloy magnetic layer of a magnetic recording medium by continuous sputtering, the power density applied to the Cr target and the Co-based alloy target is set to 1.
49-17.9 (W/CI!t) and 0.43-5
．． 17 (W/cr/I), the magnetic properties of this medium are Hc〉7500e, Breδ〉3
No. 50G μm.

It is designed to satisfy s*>o, go.

[Embodiments of the invention]

The present invention will be explained below based on examples.

Since the apparatus used in the present invention is similar to that shown in FIG. 3, a description thereof will be omitted. Here, Cr and Co-3Qat%Ni-7,5at%Cr alloy are used as targets, and the magnetic recording medium having the structure shown in Figure 2 is to be manufactured, and other main film-forming conditions are exactly the same as above. The same settings were made, the tray conveyance speed was selected and the sputtering power density of each target was varied so that Cr was lower. Table 1 shows the combinations of tray conveyance speed and sputtering power density for each target.

Table 1 The magnetic properties of the medium at this time were established using a sample vibrating wheel magnetometer (vSM), and the horizontal axis represents the sputtering power density of the magnetic alloy target, and the vertical axis represents Hc, Br・δ, and S*, respectively. Plotting the values yields the diagram shown in FIG. From Figure 1, the magnetic properties increase as the sputtering power density applied to the target increases.
It can be seen that the unit time depends on the film formation rate of the vehicle. Preferable magnetic properties Hc〉75Q Oe, Br-δ
From the results shown in Figure 1, the power density of the magnetic alloy target that satisfies >350GIIAm, S >0.8 is 0.
The power density is in the range of 43 to 5.17 W/1ffl, so the power density applied to the Cr target at this time is 1.
49 to 17.9 W/d. The upper limit of power density is 1
7.9 W/cI! The reason for choosing t is that if the temperature is higher than this, the temperature of the target will rise too much, which is not preferable for the sputtering apparatus.

〔Effect of the invention〕

A magnetic recording medium obtained by successively sputtering a Cr underlayer and a Co-based magnetic alloy layer on a Ni-P plating layer coated on a substrate has a high magnetic coercive force, residual magnetic flux density, and squareness ratio. However, in the present invention, the optimum sputtering power density applied to the Cr target and the Co-based magnetic alloy target is 1.49 to 17.9 W/CII and 0.43 W/CII, respectively. ~5.1
Because it was set to 7W/d, Hc-7500e, Br-
It has become possible to obtain a recording medium with excellent magnetic properties satisfying a>350G-μm and 8>0.80, and it has become possible to realize a high recording density.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the sputtering power density applied to a magnetic alloy target and the magnetic properties of the medium, FIG. 2 is a sectional view of the configuration of a magnetic recording medium, and FIG. 3 is a model sectional view of a sputtering chamber. 1, la: substrate, 3: underlayer, 4: magnetic layer, 6: chamber, lO: tray, 12: Cr target, 13
:Magnetic alloy target. Magnetic 1 Alloy Missing - Substance added to the case
degree (W7(,,ri Fig. 1

Claims (1)

[Claims] 1) A substrate whose main surface is plated with Ni-P is heated in an evacuated chamber, then Ar gas is introduced into the chamber, and Cr and Co-based magnetic alloy targets are continuously sputtered. In the method for manufacturing a magnetic recording medium, in which a Cr underlayer and a Co-based magnetic alloy layer are laminated in this order on the Ni-P plating layer, the power density applied to the Cr target is 1.49 to 17.9 W/cm. ^3
A method for manufacturing a magnetic recording medium, characterized in that a power density applied to the Co-based magnetic alloy target is 0.43 to 5.17 W/cm^3.