JPH05325183A - Manufacture of magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk whose coercive force is high by a method wherein the segregation amount of Cr whose segregation is promoted by increasing a substrate temperature in a grain boundary inside a CoCr-based alloy magnetic-substance layer is not reduced by a nondiffusible element constituting a protective layer. CONSTITUTION:When a magnetic disk is manufactured by sequentially forming a magnetic-substance layer and a protective layer on a substrate at a substrate temperature of 250 deg.C or higher by means of a sputtering method, a nondiffusible element which is not diffused into the magnetic-substance layer at said substrate temperature, e.g. Zr, is used as the constituent material of the protective layer.

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 can obtain a magnetic disk having a high coercive force.

[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 magnetic disk devices and the density of magnetic disks have been increased. In order to improve the recording density, it is necessary to reduce the thickness of the recording medium (magnetic layer). From this point, a sputtered thin film magnetic disk having a structure in which a magnetic layer is formed on a substrate by a sputtering method has been attracting attention as an alternative to the coating type magnetic disk in which the reduction in the thickness of the medium is seen. Has been put to practical use.

Further, reducing the thickness of the magnetic layer (magnetic layer) and increasing the coercive force (Hc) are effective means for improving the recording density. Therefore, in the past, in sputtered thin-film magnetic disks, in order to increase the coercive force, the substrate temperature was set higher than the normal temperature of 150 to 250 ° C, and the magnetic layer made of CoCr-based alloy such as CoNiCr was placed on the substrate. A method is known in which a magnetic disk is produced by sequentially forming a body layer (magnetic layer) and a protective layer by a sputtering method (for example, Ishikawa et al., 11th Annual Meeting of the Japan Society for Applied Magnetics, Abstracts, 1pA-10, p.18, 1987,
Horikawa et al., Proc. Of the 14th Japan Society for Applied Magnetics, 8
pB-16, p.27, 1990).

In the magnetic disk manufacturing method as described above, a protective layer is formed on the magnetic layer made of a CoCr alloy.
A C protective layer made of C (carbon) is formed. It is believed that the reason for the improvement in coercive force is that the segregation of Cr to the grain boundaries in the CoCr-based alloy magnetic layer is promoted by raising the substrate temperature above the normal temperature. ..

[0005]

However, in this conventional technique, for example, when the CoCr alloy magnetic layer and the C protective layer are sequentially formed with the substrate temperature higher than 300 ° C. However, there is a problem that the coercive force is lowered.
Therefore, as a result of repeated research on the cause of this decrease in coercive force, the present inventors formed a CoCr-based alloy magnetic layer and a C protective layer in this order on the substrate by a sputtering method at a substrate temperature of 250 ° C or higher. In this case, it was found that C, which is a constituent material of the protective layer, diffuses into the CoCr alloy magnetic layer.

The present invention was conceived based on the above findings, and a magnetic layer and a protective layer were sequentially formed on a substrate at a substrate temperature of 250 ° C. or higher by a sputtering method to obtain a magnetic layer. When a disk is manufactured, a non-diffusible element that does not diffuse into the magnetic layer at the substrate temperature is used as a constituent material of the protective layer so that a magnetic disk having a high coercive force can be obtained. The purpose is to provide a method.

[0007]

In order to achieve the above object, a method of manufacturing a magnetic disk according to the present invention is a sputtering method in which a magnetic layer and a protective layer are sequentially formed on a substrate at a substrate temperature of 250 ° C. or higher. In the method for producing a magnetic disk by using the above method, a non-diffusible element that does not diffuse into the magnetic layer at the substrate temperature is used as a constituent material of the protective layer.

[0008]

[Function] As a result of repeated research on the cause of the above-mentioned decrease in coercive force, the present inventors found that the CoCr alloy magnetic layer and the C protective layer were sequentially formed on the substrate by the sputtering method at a substrate temperature of 250 ° C. or higher. When forming, C, which is the constituent material of the C protective layer, is Co
It was found that the Cr-based alloy magnetic material diffuses into the layer. From this, it is assumed that the segregation amount of Cr, in which the segregation is promoted by increasing the substrate temperature at the crystal grain boundary in the CoCr-based alloy magnetic layer, is decreased by the diffusion of C, and the coercive force is reduced. Thought. In addition, a Cr underlayer, a magnetic layer, made of, for example, Cr, which is a non-magnetic element and is widely used,
In a magnetic disk having a structure having a C protective layer in order,
It is considered that when a C protective layer is formed on the magnetic layer, Cr segregated from the Cr underlayer to the crystal grain boundaries in the magnetic layer is attracted, and the amount of Cr segregation decreases, resulting in a decrease in coercive force. It was On the substrate, Cr underlayer, CoCr alloy magnetic layer,
Also in a magnetic disk with a structure having a C protection layer,
From the above, it was considered that the amount of Cr segregated in the CoCr-based alloy magnetic layer was reduced and the coercive force was reduced.

Therefore, as a constituent material of the protective layer, 250 ° C.
By using a non-diffusible element that does not diffuse into the magnetic layer at the above substrate temperature, it is possible to obtain a magnetic disk with a high coercive force by eliminating the decrease in the amount of Cr segregation at the grain boundaries in the magnetic layer. I did it. As the non-diffusible element forming the protective layer, Li, Be, B, Na, M
g, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Mn, F
e, Co, Ni, Cu, Zn, Ge, As, Se, Sr, Y, Zr, Nb, M
o, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, I, Ba, L
a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, and Bi, or one of H, Li, Be, and B
, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K,
Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, G
e, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, P
d, Ag, Cd, In, Sn, Sb, Te, I, Ba, La, Ce, Pr, N
d, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, T
Two or more kinds selected from the group of a, W, Re, Os, Ir, Pt, Au, Tl, Pb, and Bi can be mentioned. In order to improve lubricity, a conventional layer using C or the like may be formed on the protective layer made of the above non-diffusing element, if necessary.

In the method according to the present invention, examples of the substrate include a carbon substrate, a tempered glass substrate, a crystallized glass substrate, a ceramic substrate, a titanium substrate, and a silicon substrate. Note that the aluminum alloy substrate and the electroless NiP plated substrate are inferior in heat resistance such as being easily deformed at a substrate temperature of 250 ° C. or higher, and are not preferable at present.

The medium material of the magnetic layer of the magnetic disk to which the method according to the present invention is applied is CoNiCr, CoCrTa,
Examples include CoCr-based alloys such as CoCrPt. Further, as the medium material of the magnetic layer having a Cr underlayer as the underlayer, CoNiPt, CoCrPt, CoCrTa, CoCrPt, etc.
γ-Fe ₂ O _{3 and the} like can be mentioned.

[0012]

Embodiments of the present invention will be described below. [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. It is then placed in a hot isostatic press (HIP) 25
HIP by applying isotropic pressure of 2000 atm while heating to 00 ℃
To process. The obtained molded body was subjected to predetermined peripheral end face processing and surface polishing to obtain a 3.5-inch carbon substrate having a thickness of 1.27 mm.

Using an in-line DC magnetron sputtering device, a carbon substrate having a thickness of 3000 as an underlayer is formed.
Å Cr layer and CoCr alloy magnetic layer 600 Å
_A magnetic disk was manufactured by sequentially forming a _62.5 Ni ₃₀ Cr _7.5 layer and a Zr layer having a thickness of 300 Å as a protective layer in this order of description. In this case, the Ar gas pressure was 3 × 10 ⁻³ Torr, the substrate temperature was changed in the range of 250 to 600 ° C. (see FIG. 1), and the magnetic disk was manufactured under each substrate temperature condition. In addition, a C layer was formed instead of the Zr layer to manufacture a magnetic disk as a comparative example.

8 × from each of these magnetic disks produced
A sample with a size of 8 mm 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. As can be seen from FIG. 1, in the magnetic disk of the comparative example, when the substrate temperature is raised above 300 ° C., C, which is a constituent material of the C protective layer, is more diffused in the Co _62.5 Ni ₃₀ Cr _7.5 layer. As it progresses, it becomes a magnetic layer.
The amount of Cr segregated at the grain boundaries in the Co _62.5 Ni ₃₀ Cr _7.5 layer decreases, and the coercive force decreases as the substrate temperature increases. On the other hand, in the method of this example, as a constituent material of the protective layer, Co _62.5
Since Zr, which is a non-diffusible element that does not diffuse into the Ni ₃₀ Cr _7.5 layer, is used, the segregation amount of Cr is promoted by increasing the substrate temperature at the grain boundary in the Co _62.5 Ni ₃₀ Cr _7.5 layer. However, it was not decreased by Zr, and the coercive force was improved as the substrate temperature was increased, and a magnetic disk having a high coercive force was obtained.

The compositions in the depth (thickness) direction of the magnetic disks according to Examples and Comparative Examples manufactured at a substrate temperature of 400 ° C. were analyzed by ESCA (electron spectroscopy).
y for chemical analysis). As a result, in the magnetic disk according to the comparative example, C Co _62.5 Ni ₃₀ Cr
Diffusion into _7.5 layers was confirmed. On the other hand, in the magnetic disk according to the example, diffusion of Zr into the Co _62.5 Ni ₃₀ Cr _7.5 layer was not observed.

Example 2 A magnetic disk was manufactured in the same manner as in Example 1 except that the following substrate was used instead of the carbon substrate as the substrate, and the coercive force of each magnetic disk was produced. Was measured. as a result,
Tempered glass substrate, crystallized glass substrate, ceramic substrate,
Even when a titanium substrate and a silicon substrate were used, a magnetic disk having a coercive force similar to that of Example 1 was obtained regardless of the types of these substrates.

[Embodiment 3] Magnetic disks were manufactured in the same manner as in Embodiment 1 except that the following constituent materials were used instead of Zr as the constituent material of the protective layer. The coercive force was measured. as a result,
Be, Mg, Al, Si, Sc, Ti, V, Cr, Cu, Zn, Ge, Y, N
b, Mo, Pd, Hf, Ta, W, Pt, Au, Pb, Bi, La, Ce, P
Even when r, Nd, and Eu were used alone to form the protective layer, a magnetic disk having a coercive force similar to that of Example 1 was obtained regardless of the types of these constituent materials.

[Embodiment 4] Magnetic disks were manufactured in the same manner as in Embodiment 1 except that the following constituent materials were used instead of Zr as the constituent material of the protective layer. The coercive force was measured. as a result,
Even when the protective layer is formed by using NiP, SiN, SiC, TiC, ZnSe, and ZnS independently, a magnetic disk having a coercive force similar to that of Example 1 is obtained regardless of the types of the constituent materials. Was obtained.

Example 5 A magnetic disk was produced in the same manner as in Example 1 except that the magnetic layer described below was formed instead of the Co _62.5 Ni ₃₀ Cr _7.5 layer. The coercive force of the magnetic disk was measured. as a result,
CoCrTa layer, CoCr layer, CoNiPt layer, CoCrPt layer, and γ-Fe ₂ O
Even when each of the _three layers was formed, a magnetic disk having a higher coercive force was obtained as compared with the case where the protective layer was formed using C.

[0020]

As described above, according to the magnetic disk manufacturing method of the present invention, a magnetic layer and a protective layer are sequentially formed on a substrate by a sputtering method at a substrate temperature of 250 ° C. or higher. In manufacturing the above, since a non-diffusible element that does not diffuse into the magnetic layer at the substrate temperature is used as the constituent material of the protective layer, it is necessary to increase the substrate temperature at the crystal grain boundary in the magnetic layer. The segregation amount of Cr, which promotes segregation, is not reduced by the non-diffusible element forming the protective layer, and a magnetic disk having a high coercive force can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a substrate temperature and a coercive force of a magnetic disk obtained according to an embodiment of the present invention.

Claims (1)

[Claims] 1. A method for manufacturing a magnetic disk by forming a magnetic layer and a protective layer on a substrate in this order by a sputtering method at a substrate temperature of 250 ° C. or higher, and at the substrate temperature as a constituent material of the protective layer. A method for manufacturing a magnetic disk, comprising using a non-diffusible element that does not diffuse into the magnetic layer.