JPH05205262A - Manufacture of magnetic disk - Google Patents

Abstract

PURPOSE:To provide a magnetic disk with high coercive force. CONSTITUTION:Co-based allay magnetic layer or that having nonmagnetic layer consisting of Cr, etc., in between as an intermediate layer is formed on a base plate. A protective layer is formed an that Co-based alloy magnetic layer and then it is heated to 250 deg.C or higher while bias voltage is applied. Compared with a method including no heating process or that consisting only of heating process, segregation of nonmagnetic element such as Cr into grain boundary within Co group allay magnetic layer is mare promoted so that the magnetic disk with high coercive force is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic disk, which has a high coercive force suitable for increasing the recording density.

[0002]

2. Description of the Related Art As is well known, in order to cope with an increase in the amount of information, the capacity of a magnetic disk and the density of a recording medium (magnetic material layer) thereof have been increased. In order to improve the recording density, it is necessary to reduce the thickness of the recording medium. From this point, as an alternative to the coating type magnetic disk in which the reduction of the film thickness of the medium is seen, a plating type magnetic disk having a structure in which a metal magnetic material layer is formed on the substrate (disk substrate) by a plating method, and Attention has been paid to a metal sputter type magnetic disk having a structure in which a metal magnetic layer is formed by a sputtering method, and a part thereof is put to practical use.

Further, increasing the coercive force is an effective means for improving the recording density. Therefore, conventionally, as a method for increasing the coercive force, a metal sputter type magnetic disk has a substrate temperature of 150 to 150
When the temperature is higher than 250 ℃, Co such as Co-Ni-Cr
A method is known in which a magnetic layer made of a system alloy is formed by a sputtering method (for example, Ishikawa et al.
Proceedings of the 11th Japan Institute of Applied Magnetics, 1pA-10, p.1
8, 1987). This method is an excellent method, but since the magnetic layer is formed at a high substrate temperature, there are problems in the apparatus such that the carrier for holding the substrate is easily heated and deformed. I am worried about mass production.

Therefore, the inventors of the present invention have found that an underlayer made of Cr, Co--Ni--, is formed on a carbon substrate made of glassy carbon.
A magnetic disk with improved coercive force can be obtained by sequentially forming a magnetic layer and a protective layer made of a Co-based alloy such as Cr and Co-Cr-Ta, and then heat-treating them at a temperature of 250 ° C or higher. This method was previously proposed (JP-A-3-
No. 205616, Proceedings of the Spring Application Society of Japan, 1990, 29a
-Y-8, p.60). In this case, a similar method is proposed for the case where the Cr underlayer is not provided.

[0005]

According to the method proposed above, a magnetic disk having improved coercive force is obtained. However, in order to meet the problem of higher recording density, there is a demand for a method of manufacturing a magnetic disk having a higher coercive force.

Therefore, an object of the present invention is to provide a method of manufacturing a magnetic disk, which is capable of obtaining a magnetic disk having a high coercive force.

[0007]

In order to achieve the above object, in the method of manufacturing a magnetic disk according to the first aspect of the present invention, a magnetic layer made of a Co alloy and a protective layer are sequentially formed on a substrate. After that, this is heat-treated at a temperature of 250 ° C. or higher with a bias voltage applied.

According to a second aspect of the present invention, there is provided a method of manufacturing a magnetic disk, wherein a magnetic layer made of a Co-based alloy is formed on a substrate,
A non-magnetic layer and a magnetic layer made of a Co-based alloy are alternately formed thereon at least once, and a protective layer is further formed on the magnetic layer made of a Co-based alloy formed at the top.
Temperature of this product is 250 ℃ with bias voltage applied.
The above is characterized by the heat treatment.

According to a third aspect of the present invention, there is provided a magnetic disk manufacturing method, in which a base layer made of Cr, a magnetic layer made of a Co alloy and a protective layer are sequentially formed on a substrate, and a bias voltage is applied to these layers. The feature is that heat treatment is performed at a temperature of 250 ° C. or higher in this state.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a magnetic disk, wherein an underlayer made of Cr is formed on a substrate, a magnetic layer made of a Co-based alloy is formed on the Cr underlayer, and then a Cr-based magnetic layer is formed thereon. The non-magnetic layer and the magnetic layer made of a Co-based alloy are alternately formed at least once, and a protective layer is further formed on the magnetic layer made of the Co-based alloy formed on the uppermost layer. The feature is that heat treatment is performed at a temperature of 250 ° C. or higher with a bias voltage applied.

[0011]

In the method according to the present invention, the magnetic layer (magnetic layer) is Co-Ni-Cr, Co-Cr-Ta, Co-Cr, Co.
Co alloys such as -P, Co-Ni-P, Co-Cr-Pt, and Co-Ni-Pt are preferable, and the mechanism for improving coercive force is considered as follows. For magnetic layer made of Co alloy
When non-magnetic elements such as Cr and P are included, the above Co
The segregation of non-magnetic elements such as Cr and P at the crystal grain boundaries of the system alloy magnetic layer is promoted more than when only heat treatment is performed. As a result, the magnetic separation of the crystal grains of the magnetic layer progresses, and the magnetic interaction is weakened, so that the coercive force is considered to be improved.

On the other hand, when the Cr underlayer is formed as the underlayer of the Co-based alloy magnetic layer on the substrate, the (110) plane of the Cr underlayer grows by increasing the thickness of the Cr underlayer. The easy axis of magnetization (C-axis) of the system-based alloy magnetic layer is easily oriented in the plane. In addition to this, by performing the heat treatment in the state where the bias voltage is applied, the diffusion of Cr from the Cr underlayer to the crystal grain boundaries of the Co-based alloy magnetic layer is further promoted,
It is considered that the coercive force is further improved as compared with the case without the Cr underlayer.

In the method according to the present invention, the heat treatment temperature must be 250 ° C. or higher. If the temperature is lower than this, the heat treatment time required for obtaining the effect of improving the coercive force is significantly lengthened, which is not preferable from the viewpoint of productivity. It should be noted that the upper limit temperature is determined because the Co-based alloy magnetic layer itself is destroyed by heat when it is higher than 1450 ° C., and there are restrictions based on the material of the magnetic disk substrate to be used. For example, when a titanium substrate is used and the heat treatment temperature is higher than 885 ° C, the crystal structure of the titanium substrate changes from the HCP (closest hexagonal lattice) structure up to then to the BCC (body centered hexagonal lattice) structure, There is an adverse effect that fine unevenness is generated on the surface of the Co-based alloy magnetic material layer or the Cr underlayer formed on the surface of the substrate, and the magnetic characteristics are deteriorated. When a crystallized glass substrate is used, its glass transition point is 750 ° C., so a temperature lower than this is preferable.

[0014]

EXAMPLES The present invention will be described below based on examples. Example 1 First, the production of a carbon substrate as a magnetic disk substrate will be described. After molding a phenol-formaldehyde resin, which is a thermosetting resin that becomes vitreous carbon after carbonization and firing, into a magnetic disk shape, Pre-baking is performed at a temperature of 1000 to 1500 ° C in a _two- gas atmosphere. Then, this is heated to 2500 ° C. by using a hot isostatic press (HIP device) and isotropic pressure of 2000 atm is applied to generate H.
IP processing. The molded body thus obtained was subjected to predetermined peripheral end surface processing and surface polishing to obtain a carbon substrate for a 3.5-inch magnetic disk having a thickness of 1.27 mm.

On the prepared carbon substrate, a Cr underlayer as an underlayer having a thickness of 3000 Å, a Co _62.5 Ni ₃₀ Cr _7.5 layer as a magnetic layer having a thickness of 600 Å, and a Zr protective layer as a protective layer having a thickness of 300 Å Were sequentially formed by a sputtering method using a DC magnetron sputtering device. The substrate temperature during formation of each layer was 250 ° C.

With respect to the sample in which each of the above layers was formed on the carbon substrate, the heating time was 1 for each in a vacuum atmosphere (vacuum degree of 30 × 10 ⁻³ Torr) and a reverse bias voltage of 300 V (V) applied. The heating temperature was changed in the range of 350 to 650 ° C. (see FIG. 1) for each minute, and the heating treatment was performed under each condition to produce a magnetic disk. In this case, the negative output terminal side of a DC power supply whose positive output terminal side was grounded was connected to the above sample, and a reverse bias voltage was applied to the sample so that the sample had a negative potential with respect to the ground potential.
In addition, as a comparative example, a magnetic disk was manufactured by performing heat treatment under the same conditions as above, even for those to which a reverse bias voltage was not applied.

8 × from each of these magnetic disks produced
A sample of 8 mm square was cut out and used as a vibrating sample magnetometer (VS
Magnetic properties were measured using M). The measurement result of the coercive force Hc is shown in FIG. The coercive force Hc before the heat treatment was also measured.
It was 00 (Oe).

As can be seen from FIG. 1, according to the method of this embodiment, the coercive force is about 200 to 400 as compared with the comparative example in which only the heat treatment is performed without applying the reverse bias voltage.
(Oe) and the magnetic disk which was raised greatly were obtained.

Example 2 A magnetic disk was manufactured by the same procedure as in Example 1 except that the Cr underlayer was omitted, and its coercive force Hc was measured. As a result, a magnetic disk having a high coercive force was obtained as compared with the magnetic disk without heat treatment and the magnetic disk with no reverse bias voltage applied and only heat treatment.

Example 3 A carbon substrate with a thickness of 3000
ÅCr underlayer and 300Åthick 1st Co_62.5Ni₃₀Cr _7.5layer
And an intermediate Cr layer as an intermediate layer with a thickness of 100Å and a thickness of 300
Å second Co_62.5Ni ₃₀Cr_7.5Layers and a Zr protective layer with a thickness of 300Å
And DC magnetron sputtering equipment at a substrate temperature of 250 ° C.
The substrate was sequentially formed by the sputtering method. Got
About the sample in a vacuum atmosphere (vacuum degree 30 × 10^-3To Torr)
The reverse bias voltage of 300 V.
The heating time to 1 minute each and the heating temperature to the range of 350 to 650 ℃.
And heat treatment under the same conditions as in Example 1.
Then, a magnetic disk was manufactured. These magnetic disks
As a result of measuring the coercive force Hc of the disc, one without heat treatment,
Compared to those that only heat treatment without applying reverse bias voltage
In all, a magnetic disk having a high coercive force was obtained.

Example 4 A carbon substrate having a thickness of 3000
ÅCr underlayer and 200Åthick 1st Co_62.5Ni₃₀Cr _7.5layer
And the first Cr intermediate layer with a thickness of 50Å and the second Co with a thickness of 200Å
_62.5Ni₃₀Cr_7.5Layer, the second Cr intermediate layer with a thickness of 50Å, and the thickness
 200Å 3rd Co_62.5Ni₃₀Cr_7.5Layers and Zr protection with a thickness of 300Å
The protective layer and the D.C.
It was sequentially formed by a sputtering method using a sputtering device. Got
Sample in a vacuum atmosphere (vacuum degree 30 × 10^-3Tor
In r), a reverse bias voltage of 300 V was applied.
In this state, heat treatment is performed under the same conditions as in Example 3.
A magnetic disk was produced. Of these magnetic disks
As a result of measuring the coercive force Hc, no
Compared to the one that only heat treatment without applying the ass voltage,
A magnetic disk having a high coercive force was obtained.

Example 5 A magnetic disk was manufactured in the same procedure as in Example 3 except that the Cr underlayer was omitted, and its coercive force Hc was measured. As a result, a magnetic disk having a high coercive force was obtained as compared with the magnetic disk without heat treatment and the magnetic disk with no reverse bias voltage applied and only heat treatment.

Example 6 A magnetic disk was manufactured in the same procedure as in Example 4 except that the Cr underlayer was omitted, and its coercive force Hc was measured. As a result, a magnetic disk having a high coercive force was obtained as compared with the magnetic disk without heat treatment and the magnetic disk with no reverse bias voltage applied and only heat treatment.

[Example 7] A magnetic disk was manufactured in the same procedure as in Example 1 except that the heat treatment was carried out in the atmosphere, and its coercive force Hc was measured. As a result, even when the heat treatment is performed in the atmosphere,
A magnetic disk having a high coercive force was obtained as compared with the case where no heat treatment was performed and the case where only heat treatment was performed without applying a reverse bias voltage.

[Embodiment 8] A titanium substrate (Kobe Steel Co., Ltd., pure titanium KS40, JIS class 1) as a magnetic disk substrate.
And a crystallized glass substrate having a composition of the SiO ₂ —Li ₂ O—Al ₂ O ₃ system were used to fabricate magnetic disks, and their coercive force
Hc was measured. In this case, a magnetic disk was manufactured by the same procedure as in Example 1 except that the carbon substrate was changed to both of the above substrates. As a result, even when a titanium substrate or a crystallized glass substrate is used as the magnetic disk substrate, it has a higher coercive force than those without heat treatment and with only heat treatment without applying a reverse bias voltage. A magnetic disk was obtained. In each of the above examples, Cr
The example of forming the underlayer, the Co-based alloy magnetic material layer, the Cr intermediate layer, the protective layer and the like by the sputtering method has been described, but the method according to the present invention is also applicable to the case where each of these layers is formed by the plating method or the like. It is possible.

[0026]

According to the method of manufacturing a magnetic disk of the first and second aspects of the present invention, a Co-based alloy magnetic material layer or a non-magnetic material layer serving as an intermediate layer is sandwiched between the upper and lower Co layers on a substrate.
This is a method in which a system alloy magnetic material layer is formed, a protective layer is formed on this Co system alloy magnetic material layer, and this is then heat-treated at a temperature of 250 ° C. or higher with a bias voltage applied. Therefore, segregation of non-magnetic elements such as Cr to the crystal grain boundaries of the Co-based alloy magnetic layer is more promoted compared to methods that do not perform heat treatment or methods that perform only heat treatment without applying a bias voltage. By doing so, the magnetic separation of the crystal grains of the Co-based alloy magnetic material layer progresses and the magnetic interaction is weakened, so that a magnetic disk having a high coercive force can be obtained. According to the magnetic disk manufacturing method of the third and fourth aspects of the invention, the action of the Cr underlayer
A magnetic disk having a higher coercive force can be obtained due to the easy axis of magnetization of the Co-based alloy magnetic layer being easily oriented in the plane and the above-mentioned effect of improving the coercive force.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of coercive force of a magnetic disk obtained by a method according to the present invention.

Claims (4)

[Claims] 1. A magnetic material layer made of a Co-based alloy and a protective layer are sequentially formed on a substrate, and then heat-treated at a temperature of 250 ° C. or higher while applying a bias voltage. Manufacturing method of magnetic disk. 2. A magnetic material layer made of a Co-based alloy is formed on a substrate, and a non-magnetic material layer and a magnetic material layer made of a Co-based alloy are alternately formed on the magnetic material layer at least once to form the uppermost layer. After further forming a protective layer on the magnetic layer made of the Co-based alloy, the temperature of this layer was increased with a bias voltage applied.
A method for manufacturing a magnetic disk, which comprises performing heat treatment at 250 ° C. or higher. 3. An underlayer made of Cr, a magnetic layer made of a Co-based alloy, and a protective layer are sequentially formed on a substrate, and then heat-treated at a temperature of 250 ° C. or higher while applying a bias voltage. A method of manufacturing a magnetic disk, comprising: 4. An underlayer made of Cr is formed on a substrate, a magnetic layer made of a Co-based alloy is formed on the Cr underlayer, and then a magnetic layer made of a non-magnetic layer and a Co-based alloy is formed thereon. Alternately formed with body layers at least once and formed on top
After forming a protective layer on the magnetic layer made of Co-based alloy, the protective layer was formed at a temperature of 2 with a bias voltage applied.
A method for manufacturing a magnetic disk, which comprises performing heat treatment at 50 ° C. or higher.