JP2935606B2 - Manufacturing method of magnetic disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic disk capable of obtaining 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, an increase in the capacity of a magnetic disk and an increase in the density of a recording medium (magnetic material layer) have been attempted. In order to improve the recording density, it is necessary to reduce the thickness of the recording medium. From this point, a plating type magnetic disk having a structure in which a metal magnetic material layer is formed on a substrate (disk substrate) by a plating method, as an alternative to a coating type magnetic disk having a limit in reducing the film thickness of the medium, 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 of the disk is practically used.

[0005] Increasing the coercive force (Hc) is also a powerful means for improving the recording density. Therefore, conventionally, as a method for increasing the coercive force, in a metal-sputtered magnetic disk, the substrate temperature is set to a normal value on the substrate.
With the temperature higher than about 150 to 250 ° C, Co-Ni-Cr,
Magnetic layer (magnetic layer) made of Co-based alloy such as Co-Cr-Ta
There is known a method in which is formed by sputtering (for example, Ishikawa et al., 11th Annual Meeting of the Japan Society of Applied Magnetics, 1pA-10, p.18, 1987). This method
Although it is excellent, since the magnetic layer is formed at a high substrate temperature, there is a problem in equipment such as the carrier for holding the substrate that is easily deformed by heating, and it is difficult for mass production. I am worried.

Therefore, the present inventors formed an underlayer made of Cr, a magnetic layer made of a Co-based alloy, and a protective layer in this order on a carbon substrate made of glassy carbon, A method has been proposed in which a magnetic disk with improved coercive force can be obtained by heat treatment at a temperature of (Japanese Patent Application No. 2-73924, Proceedings of the Spring Meeting of the Japan Society of Applied Physics, 1990, 29a-Y-8, p.60). In this case, a similar method is proposed for a magnetic disk having no Cr underlayer.

According to this method of manufacturing a magnetic disk, it is considered that the coercive force is improved by the following action mechanism. That is, the nonmagnetic element Cr
In the case where Cr is contained, the heat treatment promotes the segregation of Cr to the crystal grain boundaries of the Co-based alloy magnetic layer. Thus, it is considered that the magnetic separation between the crystal grains in the Co-based alloy magnetic layer progresses, and the magnetic interaction between the crystal grains weakens, thereby improving the coercive force. When a Cr underlayer is formed on the substrate, the (110) plane of the Cr underlayer is selectively grown by increasing its thickness,
The easy axis of magnetization (C axis) of the Co-based alloy magnetic layer is easily oriented in the plane, so that the anisotropic magnetic field is increased .
Further, it is considered that by performing the heat treatment, the diffusion of Cr from the Cr underlayer to the crystal grain boundaries of the Co-based alloy magnetic layer is promoted, so that the coercive force is improved.

[0006]

However, in the process of carrying out the method proposed above, a layer of C (carbon), which is a typical substance, is formed on the Co-based alloy magnetic layer as a protective layer. When the heat treatment is performed after forming the layer, C
C is diffused into the Co-based alloy magnetic layer, and reacts with, for example, Cr, which is a non-magnetic element in the Co-based alloy magnetic layer, to form Cr.
It was found that a -C compound was formed. It has been found that the diffusion of C forming the protective layer into the Co-based alloy magnetic layer due to the heat treatment is an obstacle to obtaining a higher coercive force without any variation.

The present invention has been conceived based on the above findings, and has as its object to provide a method for manufacturing a magnetic disk capable of obtaining a magnetic disk having a high coercive force.

[0008]

Means for Solving the Problems To achieve the above object, the invention of claim 1 of the present application is to form a magnetic layer made of a Co-based alloy and a protective layer on a substrate in this order, In a method for producing a magnetic disk by heating at a temperature of 250 ° C. or higher, wherein the heat treatment is performed on the protective layer.
It is characterized by being formed using Zr or Ta , which is an element that does not diffuse into the Co-based alloy magnetic layer.

Further, the invention of claim 2 of the present application provides
A method for manufacturing a magnetic disk by forming a base layer made of Cr, a magnetic layer made of a Co-based alloy, and a protective layer in this order, and then performing a heat treatment at a temperature of 250 ° C. or more, wherein the protective layer is It is characterized by being formed using Zr or Ta , which is an element that does not diffuse into the Co-based alloy magnetic layer when subjected to heat treatment.

[0010]

In the method of manufacturing a magnetic disk according to the first aspect of the invention, when the Co-based alloy magnetic layer contains, for example, Cr, which is a non-magnetic element, the Co-based alloy magnetic layer is subjected to heat treatment. The segregation of Cr at the grain boundaries is promoted. In this case, the protective layer is made of Zr or Ta, which is an element that does not diffuse into the Co-based alloy magnetic layer when subjected to the heat treatment. Therefore, the elements forming the protective layer and
Since a Cr compound with Cr in the Co-based alloy magnetic layer is not generated, the segregation of Cr at the crystal grain boundaries of the Co-based alloy magnetic layer is further promoted. As a result, it is considered that the magnetic interaction between the crystal grains in the Co-based alloy magnetic material layer is weakened, so that the coercive force is further improved.

In the method for manufacturing a magnetic disk according to the present invention, a nonmagnetic element, for example, Cr in the Co-based alloy magnetic layer and a compound of an element forming a protective layer are formed by heat treatment. Is not generated, so that the segregation of Cr at the crystal grain boundaries of the Co-based alloy magnetic layer is further promoted in the same manner as described above. In addition to this,
Since the Cr underlayer is provided, by increasing its thickness, the (110) plane of the Cr underlayer is selectively grown, and the axis of easy magnetization (C axis) of the Co-based alloy magnetic layer is in-plane. In addition to increasing the anisotropic magnetic field by being easily oriented,
It is considered that by performing the heat treatment, the diffusion of Cr from the Cr underlayer to the crystal grain boundaries of the Co-based alloy magnetic layer is promoted, so that the coercive force is improved.

In the method of manufacturing a magnetic disk according to the present invention, the Zr formed on the Co-based alloy magnetic material layer
Or the protective layer made of Ta is oxidized by the heating atmosphere.
The Co-based alloy magnetic layer is chemically and
A non-magnetic protective layer having a function of mechanical protection.

[0013]

This Zr and Ta can be formed (layer formed) by various methods such as a vapor deposition method and a chemical vapor deposition method as well as the sputtering method . In the method according to the present invention ,
As a method of forming the Co-based alloy magnetic layer and the Cr underlayer,
Not limited to the sputtering method, various methods such as a vapor deposition method, a chemical vapor deposition method, and a plating method can be adopted.

In the method for manufacturing a magnetic disk according to the present invention, the heat treatment temperature is 250 ° C. or higher. If the temperature is lower than 250 ° C., the time required for the heat treatment is long in order to obtain the effect of improving the coercive force, which is not preferable. The upper limit temperature is
If the temperature is higher than 1450 ° C., it is determined because the Co-based alloy magnetic layer itself is destroyed by heat and there are restrictions based on the material of the magnetic disk substrate. For example, when a titanium substrate is used, the heat treatment temperature is 885
If the temperature is higher than ℃, the crystal structure of the titanium substrate
The structure changes from a P. (closest-packed hexagonal lattice) structure to a BCC (body-centered hexagonal lattice) structure, and fine irregularities occur on the surface of the magnetic layer or Cr underlayer formed on the titanium substrate surface. Has the adverse effect of deteriorating its characteristics. When a crystallized glass substrate is used, its glass transition point is 7
Since the temperature is 50 ° C., a lower temperature is preferable.

The magnetic disk substrate used in the method according to the present invention includes a carbon substrate, a titanium substrate,
Examples include a crystallized glass substrate, a tempered glass substrate, and a silicon substrate.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. First, an embodiment of the present invention will be described below. [Example 1] First, the production of a carbon substrate as a substrate for a magnetic disk will be described. A phenol / formaldehyde resin, which is a thermosetting resin which becomes vitreous carbon after carbonization and firing, is formed into a magnetic disk shape. _2. Pre-fire at a temperature of 1000 to 1500 ° C in a gas atmosphere. Then, this is heated to 25% using a hot isostatic press (HIP).
HIP by applying isotropic pressure of 2000 atm while heating to 00 ° C
To process. The obtained molded body was subjected to predetermined peripheral end face processing and surface polishing to obtain a carbon substrate for 3.5 inches with a thickness of 1.27 mm.

On the prepared carbon substrate, a Cr layer having a thickness of 3000 mm as an underlayer, and a 600 nm thick layer as a Co-based alloy magnetic layer.
Co Co _62.5 Ni ₃₀ Cr _7.5 layer and thickness 300 as protective layer
The Zr layer was sequentially formed using a DC magnetron sputtering apparatus. The substrate temperature was 250 ° C. The obtained product was subjected to a heat treatment in a vacuum atmosphere (degree of vacuum: 30 × 10 ⁻³ Torr) with a heating time of 1 minute and a heating temperature of 350 to 650 ° C. (see FIG. 1). A magnetic disk was manufactured for each heating condition.

Further, a substrate having a C layer provided in place of the above-mentioned Zr layer was prepared, and this was formed in a vacuum atmosphere (degree of vacuum 30 ×).
10 ^-3 Torr), set the heating time to 1 minute each, and set the heating temperature
Heat treatment was performed at a temperature in the range of 450 to 600 ° C. (see FIG. 1) to produce a magnetic disk as a comparative example under each heating condition.

From each of these magnetic disks produced, 8 ×
A sample having a size of 8 mm was cut out, each layer on one side was removed, and the magnetic properties were measured using a vibrating sample magnetometer (VSM). FIG. 1 shows the measurement results of the coercive force Hc. Note that the coercive force Hc before the heat treatment was also measured for those having the Zr layer and those having the C layer. Without these heat treatments, the coercive force Hc was about 1000 (Oe).

As can be understood from FIG. 1, according to the method of this embodiment, Zr and Co _62.5 Ni
Compounds with Cr in the ₃₀ Cr _7.5 layer are not generated,
Since the segregation of Cr in the grain boundary of Co _{62 .5} Ni ₃₀ Cr _7.5 layer is further promoted, which do not heat treated, as compared to the magnetic disk of Comparative Example, the coercive force Hc greatly improved without variation A magnetic disk was obtained.

In addition, thin film X-ray diffraction and ESCA analysis (electron spect
As a result of roscopy for chemical analysis), it was found that the Zr layer was changed to an oxidized Zr layer by the heat treatment. The sample was kept in an atmosphere at a temperature of 65 ° C. and a humidity of 85% for 10 days. After this environmental test, the magnetic properties were measured using a vibrating sample magnetometer. As a result, the coercive force Hc,
The values of the residual magnetic flux density Br and the squareness m did not change compared to before the environmental test, and it was confirmed that the Zr oxide layer has a function as a protective layer.

The C layer of the magnetic disk of the comparative example reacts with oxygen by heat treatment in a vacuum to be gasified as CO ₂ and its thickness is reduced. For example, a 300-mm thick C layer has a thickness of 82 mm when heated at 300 ° C for 1 minute.
The thickness decreased by 118 ° when heat-treated at 400 ° C for 1 minute, and decreased by 268 ° when heat-treated at 500 ° C for 1 minute. In contrast, the thickness of the Zr layer was not reduced by the heat treatment in vacuum.

Example 2 A magnetic disk was manufactured in the same manner as in Example 1 except that the heat treatment was performed in an air atmosphere instead of the heat treatment in a vacuum atmosphere. FIG. 2 shows the measurement results of the coercive force Hc of the obtained magnetic disk.
Shown in As can be understood from the figure, even when the heat treatment is performed in the air atmosphere, a magnetic disk having no heat treatment and a magnetic disk having significantly improved coercive force Hc as compared with the magnetic disk of the comparative example of Example 1 are obtained. Was done.

[0025]

Example 3 A magnetic disk was manufactured in the same manner as in Example 1 except that a Ta layer was formed instead of a Zr layer as a protective layer. FIG. 3 shows the measurement results of the coercive force Hc of the obtained magnetic disk. As can be understood from the figure, by performing the heat treatment, even if the protective layer is formed using Ta,
And the coercive force as compared with the comparative magnetic disk of Example 1.
A magnetic disk with greatly improved Hc was obtained. The composition analysis in the depth (thickness) direction of the magnetic disk of this example was performed by ESCA analysis. As a result, it was found that the Ta layer was changed to an oxidized Ta layer by the heat treatment. Further, as a result of the same environmental test as in Example 1, the coercive force
The values of Hc, residual magnetic flux density Br, and squareness m did not change compared to before the environmental test, and it was confirmed that the Ta oxide layer had a function as a protective layer.

[0027]

[0028]

[0029]

[0030]

[0031]

Example 4 A magnetic disk substrate was replaced by a titanium substrate (Pure Titanium KS40, JIS Class 1) instead of a carbon substrate.
A magnetic disk was manufactured in the same manner as in Example 1. FIG. 4 shows the measurement results of the coercive force Hc. As can be understood from the figure, by performing the heat treatment, even when the titanium substrate was used, a magnetic disk having a significantly improved coercive force Hc was obtained as compared with the case where the heat treatment was not performed.

Example 5 Example 1 was repeated except that a crystallized glass substrate having an SiO ₂ -Li ₂ O-Al ₂ O ₃ composition was used as the magnetic disk substrate instead of the carbon substrate. A magnetic disk was produced in the same manner as described above. Coercive force Hc
FIG. 5 shows the measurement results. As understood from the figure,
By performing the heat treatment, even when a crystallized glass substrate was used, a magnetic disk having a significantly improved coercive force Hc was obtained as compared with the case where no heat treatment was performed.

Example 6 A magnetic disk was manufactured in the same manner as in Example 1, except that a strengthened glass substrate was used instead of the carbon substrate as the magnetic disk substrate. FIG. 6 shows the measurement results of the coercive force Hc. As can be understood from the figure, by performing the heat treatment, even when the tempered glass substrate was used, a magnetic disk having a significantly improved coercive force Hc was obtained as compared with the case where the heat treatment was not performed.

Example 7 A magnetic disk was manufactured in the same manner as in Example 1 except that a silicon (Si) substrate was used instead of the carbon substrate as the magnetic disk substrate. FIG. 7 shows the measurement results of the coercive force Hc. As can be understood from the figure, by performing the heat treatment, a magnetic disk having significantly improved coercive force Hc was obtained even when a silicon substrate was used, as compared with the case where no heat treatment was performed.

Next, an embodiment of the present invention will be described below. Example 8 On a carbon substrate, a Co _62.5 Ni ₃₀ Cr _7.5 layer with a thickness of 600 mm as a Co-based alloy magnetic layer and a Zr layer with a thickness of 300 mm as a protective layer were sequentially formed using a DC magnetron sputtering apparatus. did. The substrate temperature was 250 ° C. The obtained product was heated in a vacuum atmosphere (degree of vacuum: 30 × 10 ⁻³ Torr) for 1 minute each at a heating temperature of 350 to 650 ° C.
(See FIG. 8 ), and heat treatment was performed to produce a magnetic disk for each heating condition. FIG. 8 shows the measurement results of the coercive force Hc. In addition, the coercive force Hc
Was about 200 (Oe). As can be understood from the figure, even with a magnetic disk having no Cr underlayer, a magnetic disk having significantly improved coercive force Hc was obtained as compared with a magnetic disk without heat treatment.

[0037]

As described above, in the method of manufacturing a magnetic disk according to the first aspect of the present invention, the magnetic disk is formed on the substrate.
When heat-treated on a magnetic layer made of a Co-based alloy, Co
A protective layer is formed using Zr or Ta , which is an element that does not diffuse into the base alloy magnetic layer, and then this is heated to a temperature.
Because it is a method of heating at 250 ° C or more,
By performing the heat treatment, the protective layer is changed to an oxide and functions as a protective layer, while the element forming the protective layer and the non-magnetic element in the Co-based alloy magnetic material layer are used. since for example a compound of Cr is prevented from being generated, so that the segregation of the Cr to the grain boundaries of the Co-based alloy magnetic layer is further promoted. Thereby, a magnetic disk having a high coercive force can be obtained by weakening magnetic interaction between crystal grains in the Co-based alloy magnetic layer.

In the method of manufacturing a magnetic disk according to the second aspect of the present invention, by performing the heat treatment, the protective layer is changed to a layer made of oxide and functions as a protective layer in the same manner as described above. On the other hand, since a compound of, for example, Cr, which is a non-magnetic element in the Co-based alloy magnetic layer and an element forming the protective layer, is not generated, it is difficult to reach a crystal grain boundary of the Co-based alloy magnetic layer. segregation of the Cr is a more is promoted. In addition to this, since the Cr underlayer is provided, the axis of easy magnetization (C-axis) of the Co-based alloy magnetic material layer is easily oriented in the plane, and the heat treatment is performed to improve the Cr. Cr from underlayer to crystal grain boundary of Co-based alloy magnetic layer
Is promoted, so that a magnetic disk having a higher coercive force can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an example of a relationship between a heat treatment temperature of a magnetic disk and a coercive force obtained according to a second embodiment of the present invention;

FIG. 3 is a diagram showing an example of a relationship between a heat treatment temperature of a magnetic disk and a coercive force obtained according to a third embodiment of the present invention;

FIG. 4 is a diagram showing an example of a relationship between a heat treatment temperature of a magnetic disk and a coercive force obtained according to a fourth embodiment of the present invention;

FIG. 5 is a diagram showing an example of a relationship between a heat treatment temperature of a magnetic disk and a coercive force obtained according to a fifth embodiment of the present invention.

FIG. 6 is a diagram showing an example of a relationship between a heat treatment temperature of a magnetic disk and a coercive force obtained according to a sixth embodiment of the present invention.

FIG. 7 is a diagram showing an example of a relationship between a heat treatment temperature of a magnetic disk and a coercive force obtained according to a seventh embodiment of the present invention.

8 is a diagram showing an example of the relationship between the heat treatment temperature and the coercivity of Example 8 thus obtained magnetic disk of the invention of claim 1.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 5/85 G11B 5/84

Claims (2)

(57) [Claims] 1. A method of manufacturing a magnetic disk by forming a magnetic layer made of a Co-based alloy and a protective layer in this order on a substrate, and heating the magnetic layer at a temperature of 250 ° C. or higher. A method for manufacturing a magnetic disk, wherein the layer is formed using Zr or Ta , which is an element that does not diffuse into the Co-based alloy magnetic layer when the layer is subjected to heat treatment. 2. A method of manufacturing a magnetic disk by forming an underlayer made of Cr, a magnetic layer made of a Co-based alloy, and a protective layer in this order on a substrate, and then heating them at a temperature of 250 ° C. or higher. In the above , Zr or Ta which is an element which does not diffuse into the Co-based alloy magnetic material layer when the protective layer is heat-treated.
A method for manufacturing a magnetic disk, comprising: