JP2001176056A - Magnetic disk and magnetic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic disk excellent in the mass productivity and the property to lower the floating height of a magnetic head. SOLUTION: In the magnetic disk which comprises a glass substrate and an information recording thin film formed directly or with other layers interposed on the substrate surface, the glass substrate contains a conducting material dispersed in a glass matrix. The conducting material is dispersed in an amount such that <=1011 Ωcm specific resistance of the glass substrate at room temperature is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk, and more particularly to a magnetic disk and a magnetic recording device which are effective for lowering the flying height of a magnetic head and which are excellent in mass productivity.

[0002]

2. Description of the Related Art Conventionally, a magnetic recording apparatus uses an Al substrate as a substrate of a magnetic disk mounted thereon. In recent years, as the capacity of a magnetic recording device has increased, a glass substrate has been used as a substrate of the magnetic disk.

[0003] The above glass substrate is superior in smoothness and flatness as compared with the Al substrate, and is hard, which is advantageous from the viewpoint of low flying height and impact resistance of the magnetic head. A glass substrate is applied to the entire surface of a small 2.5-inch magnetic recording device mounted on a notebook personal computer.

[0004] These glass substrates are disclosed in
239030, JP-A-7-223845, JP-A-9
As described in JP-A-249431 or JP-A-9-249432, a chemically strengthened glass substrate whose surface is ion-exchanged to increase the strength is used.

Further, as described in JP-A-7-187711 and JP-A-7-300340, a crystallized glass substrate is used in which a high-hardness crystal is precipitated by heat treatment to increase the strength. .

As a 2.5-inch magnetic disk, an information recording thin film is formed on a glass substrate by a sputtering method or the like. In practice, an underlayer intervenes between the information recording thin film and the glass substrate, and a protective layer is often formed on the information recording thin film surface. Further, a lubricating liquid is applied to the surface of the magnetic disk.

On the other hand, the magnetic head flies above the information recording surface of the magnetic disk when the magnetic disk rotates, and repeats recording and reproducing operations.

[0008]

The recording capacity of a magnetic recording device is increasing at an annual rate of about 80%, and a further increase in the capacity is required in the future. In order to increase the capacity, in addition to the materials used for the magnetic disk and the magnetic head and the high performance due to the configuration, the flying height of the magnetic head on the information recording surface of the magnetic disk is further reduced, It is necessary that recording and reproduction can be efficiently performed on a minute portion of the recording surface.

However, on the other hand, the low flying height of the magnetic head is
There is a problem that the production yield of the magnetic disk is reduced.

In order to reduce the flying height of the magnetic head, it is necessary to remarkably improve the smoothness and flatness of the glass substrate used for the magnetic disk and also to increase the cleanliness of the substrate surface. Recently, advanced glass processing technology and cleaning technology have been used, but in particular, the degree of cleanliness has been limited from the viewpoint of glass material.

A chemically strengthened glass substrate as described in JP-A-1-239030 and the like and
A crystallized glass substrate as described in JP-187711 is generally insulative, and even after advanced processing and cleaning, dust and the like once removed by cleaning are reattached by static electricity. It turned out that there was.

Actually, a magnetic disk is manufactured in a clean room where the amount of dust and the like is very small. However, even in the case of cleaning and handling, extremely fine dust may be attached to the magnetic disk, thereby lowering the manufacturing yield of the magnetic disk. . Further, as the flying height of the magnetic head has been reduced, there has been an important problem in improving the manufacturing yield.

In a magnetic disk manufactured using a glass substrate to which such dust has adhered, when the magnetic head slides, the adhered dust and the like forms a protruding portion, and the magnetic head collides with the projecting portion. In some cases, important information recorded was lost due to scratching.

An object of the present invention is to provide a magnetic disk which is effective for lowering the flying height of a magnetic head and has an excellent manufacturing yield, and a magnetic recording apparatus using the same.

[0015]

The gist of the present invention to achieve the above object is as follows.

[1] In a magnetic disk having a glass substrate and an information recording thin film formed directly or via another layer on the surface of the substrate, the glass substrate has a conductive material dispersed in a glass matrix. The magnetic disk is characterized in that the material is dispersed in such a quantity that the specific resistance of the glass substrate at room temperature becomes 10 ¹¹ Ω · cm or less.

The specific resistance of the glass substrate is as follows:
It is particularly preferred that it is not more than 10 ⁹ Ω · cm.

[2] The magnetic disk in which the conductive material is conductive fine particles. The conductive fine particles include metal or noble metal fine particles. Further, metal ions are particularly preferable as the conductive material, and Nb,
A transition metal ion selected from Ti, Sn, Co, Fe, and V is preferable.

[3] The above magnetic disk has a surface roughness Ra of the information recording surface of 0.6 nm or less.

[4] A magnetic disk, a magnetic head,
In a magnetic recording apparatus including a rotating unit for rotating a magnetic disk and a moving unit for moving a magnetic head in parallel to a surface of the magnetic disk, the magnetic disk includes a glass substrate,
An information recording thin film formed directly or through another layer on the substrate surface, and an information recording thin film formed directly or through another layer on the substrate surface, wherein the glass substrate is made of glass. A conductive material is dispersed in the matrix, the specific resistance at room temperature is 10 ¹¹ Ω · cm or less, and the surface roughness Ra of the information recording surface is 0.6 nm or less, An average flying height of a magnetic head with respect to a magnetic disk surface during recording and reproduction is 23 nm or less. In particular, the glass substrate preferably has a specific resistance at room temperature of 10 ⁹ Ω · cm or less.

[5] The magnetic recording device has two or more magnetic disks mounted thereon, and the spacers provided between the magnetic disks are glass spacers having the same composition or the same components as the glass substrate but having different component ratios. In the magnetic recording device provided with:

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described based on embodiments.

[Examples 1 to 8] Using the glass substrates shown in Table 1, 2.5 inch magnetic disks were manufactured.

[0024]

[Table 1]

In order to match the thermal expansion of the glass substrate of Table 1 with other members such as the information recording thin film and the spacer, a temperature range of 100 to 300 ° C. (70 to 100) ×
The coefficient of thermal expansion was 10 to ⁷ / ° C. The surface roughness Ra of the information recording surface of the glass substrate was 0.6 nm, and the thickness of the glass substrate was 0.635 mm.

Regarding the cleanliness of the glass substrates, all the substrates are placed in a dedicated clean room for manufacturing magnetic disks.
Scrubble washing was performed using a polyvinyl alcohol brush, and drying after washing was by natural drying.

The specific resistance of the dried glass substrate and the average number of foreign substances on the recording surface of the substrate were measured by an SEM image and an optical microscope, and are shown in Table 1.

The specific resistance (Ω · cm) was determined by forming electrodes on the upper and lower recording surfaces of a glass substrate with an Ag paste, measuring the resistance between the electrodes, and converting the resistance to obtain the specific resistance. . This specific resistance is a measured value at room temperature.

The average number of foreign particles was obtained by measuring the number of foreign particles having a size of 0.3 μm or more adhering to the entire recording surface of the substrate and converting the number per unit area. The number of foreign substances was measured for five substrates. That is, the average number of foreign substances was shown by converting the measured values on the 10 recording surfaces per unit area.

Comparative Example a in Table 1 is an aluminosilicate glass substrate which has been subjected to a chemical strengthening treatment for increasing the strength of the substrate by alkali ion exchange on the surface of the glass substrate, and Comparative Example b is a soda lime glass which has also been subjected to the chemical strengthening treatment. The substrate, Comparative Example c is a lithium silicate glass substrate subjected to crystallization strengthening treatment, and Comparative Example d is an aluminoborosilicate glass substrate not subjected to special strengthening treatment such as a to c.

The glass substrates of Comparative Examples a to d are already 2.
This is a conventional substrate applied to a 5-inch magnetic disk or the like, or a substrate to be used in the future. They had a high specific resistance at room temperature of 10 ¹² Ω · cm or more and were electrically insulating. In addition, the average number of foreign matters is as large as 6 / cm ² or more,
In order to achieve both low flying height of the head and improvement in production yield, it was necessary to make the value less than 1/3 of the above value.

On the other hand, in Examples A to C, Au, P
t, conductive fine particles made of a noble metal of Ag
It is a glass substrate with 67% dispersion. Here, the reason why the amount of dispersion is set to 12 to 67% is that if it is less than 12%, the glass conductivity becomes small, and if it exceeds 67%, the surface roughness Ra of the information recording surface of the substrate becomes larger than 0.6 nm. It is because.

In Examples C to H, CoO, Nb ₂ O ₅ ,
The _{TiO 2, SnO 2, Fe 2} O 3, metal oxide selected from V ₂ O _5, a glass substrate which contains 18 to 58 wt%.

If the content of the metal oxide is less than 18% by weight, the glass conductivity becomes low, and if it exceeds 58% by weight, the mechanical strength of the glass substrate is reduced.

The glass substrates of Examples A to H exhibited low specific resistances at room temperature of 10 ¹¹ Ω · cm or less by dispersing conductive fine particles or metal ions.

It should be noted that the same effect can be obtained with a substance other than the fine particles or metal ions shown in the examples of Table 1 if the substance having the above conductivity is present in the glass substrate in an appropriate amount. It is considered something.

The average number of foreign substances on the glass substrates of Examples A to H was very small, less than 2 / cm ² . In particular, in the glass substrates of Examples C, F, G, and H having a specific resistance of 10 ⁹ Ω · cm or less, the average number of foreign matters was remarkably small at 0.5 / cm ² or less.

Next, FIG. 1 shows the relationship between the specific resistance of the glass substrate and the average number of foreign substances. As can be seen from the figure, the average number of foreign substances increases as the glass substrate has a higher specific resistance. Specific resistance is 10 ⁹ Ω
・ Below cm, the average number of foreign substances is extremely small, 10 ¹¹ Ω
cm, the average number of foreign substances significantly increased in the region exceeding 10 ¹³
It can be seen that the average number of foreign substances exceeds 8 / cm ² at Ω · cm or more.

FIG. 2 is a schematic sectional view of a magnetic disk manufactured using the glass substrates shown in Table 1. A precoat film 2, a base film 3, a magnetic film 4, and a protective film 5 were sequentially formed on a glass substrate 1, and a lubricant 6 was applied thereon.

In this embodiment, a Cr-based precoat film (thickness: 15 nm) is used as the precoat film 2, and a CrTi
A CoCrPt-based magnetic film was used for the magnetic underlayer and the magnetic film 4, and a carbon protective film was used for the protective film 5.

Next, an outline of a method of manufacturing a magnetic disk will be described. A Cr-based precoat film 2 (thickness: 15 nm) was formed on both surfaces of the glass substrate 1 shown in Table 1 by sputtering.
i-based base film 3 (thickness: 20 nm), CoCrPt-based magnetic film 4 (thickness: 20 nm), carbon protective film 5 (thickness: 1 nm)
0 nm). At this time, the Cr-based precoat film 2 was at room temperature, and the other films were at a glass substrate temperature of 250 to
The film was formed at 300 ° C. The sputtering rate of each film is 1
The range was from 00 to 300 nm / min.

Further, a perfluoropolyether-based lubricant 6 was applied by dipping to produce a magnetic disk shown in the schematic sectional view of FIG. The number of magnetic disks manufactured was 100 for each glass substrate shown in Table 1.

Next, a magnetic head flying test was carried out using each of the manufactured 100 magnetic disks. The flying height of the magnetic head was set to four types of 33 nm, 28 nm, 23 nm, and 19 nm, and the test was performed in the descending order of the flying height, and the yield (the number of good products) at each flying height was examined. The flying height of the magnetic head was the distance from the lower surface of the magnetic head to the upper surface of the carbon protective film 5. In the magnetic head flying test, the magnetic head was slid on both surfaces of the produced magnetic disk at the above-mentioned flying height, and was classified into a defective product and a non-defective product according to the presence or absence of an error due to heat generation at the time of collision with the magnetic head. The rotation speed of the magnetic disk was 5,000 rpm. Table 2 summarizes the results of these measurements.

[0044]

[Table 2]

In Comparative Examples 1 to 4, glass substrates a to d were used. As the flying height of the magnetic head decreased, the yield of the magnetic disk decreased. In particular, the decrease was remarkable when the flying height of the magnetic head was 23 nm or less. In addition, the yields of Comparative Examples 1 to 4 tend to be lower as the substrate has a larger number of foreign substances.

On the other hand, in Examples 1 to 8, since the glass substrates A to H having a small number of foreign matters were used, a better yield was obtained as compared with the comparative example. Magnetic head flying height is 2
At 3 nm or more, a yield of 90% or more was achieved.

On the other hand, in the comparative example, the flying height of the magnetic head was 33
A yield of 90 nm or more was achieved at nm, but was reduced to about 84% at 27 nm and further to 40 to 50% at 23 nm. At 19 nm, the yield was remarkably reduced to about 20%.

In this embodiment, the flying height of the magnetic head is as high as 70% or more even at the flying height of 19 nm. In particular, in the embodiments 3, 6, 7 and 8, the flying height is at least 90%. Examples 3, 6, 7, and 8 used glass substrates C, F, G, and H. As shown in Table 1 and FIG. 1, particularly, the specific resistance was low and the average number of foreign substances was very small, and thus excellent. Showed yield.

From the above, it has been found that a glass substrate having a lower specific resistance has a smaller number of foreign substances adhering thereto, and a glass substrate having a smaller number of foreign substances has a higher yield of a magnetic disk and is more effective for lowering the flying height of a magnetic head. Specifically, it is effective that the specific resistance of the glass substrate is 10 ¹¹ Ω · cm or less.
0 ⁹ Ω · cm or less is clear that more preferable.

Such a glass substrate can be obtained, for example, by dispersing conductive fine particles in a glass matrix or by including a transition metal ion. When the surface roughness Ra of the information recording surface of the glass substrate is 0.6 nm or less, the yield of the magnetic disk when the flying height of the magnetic head is 23 nm or less is much higher than before.

[Examples 9 to 12] A 2.5-inch magnetic disk was manufactured using the glass substrates E, G, and a in Table 1, and a study was made to reduce the flying height of the magnetic head.

The thickness of the glass substrate is 0.635 mm,
The surface roughness Ra of the information recording surface of the glass substrate was two types, 0.6 nm and 0.3 nm. Regarding the cleanliness of the glass substrate, scrubbing was performed in a dedicated clean room for manufacturing a magnetic disk in the same manner as in the above embodiment.

The average number of foreign particles due to the difference in the surface roughness Ra of the information recording surface of the glass substrate was slightly smaller when Ra was smaller, but was substantially the same. The method for measuring the average number of foreign particles was the same as in Example 1. Next, using these glass substrates, 100 magnetic disks of FIG. 2 were manufactured in the same manner as in Example 1.

At this time, the thickness of the Cr-based precoat film 2 was 9 nm, the thickness of the CrTi-based
The system magnetic film 4 was 14 nm, and the carbon protective film 5 was 6 nm. Lubricant 6 was applied by spin coating.

A magnetic head levitation test was performed using each of the 100 manufactured magnetic disks. The flying height of the magnetic head from the lower surface of the magnetic head to the upper surface of the carbon protective film 5 of the magnetic disk was set to 19 nm, 16 nm, 12 nm, and 9 nm, and the flying height was tested in descending order, and the yield at each flying height (non-defective product) Number). In the magnetic head flying test, the magnetic head was slid at the above-mentioned flying height on both surfaces of the magnetic disk produced in the same manner as in Example 1, and was classified into a defective product and a non-defective product according to the presence or absence of an error due to heat generated at the time of collision with the magnetic head.
The rotation speed of the magnetic disk was 6,000 rpm. Table 3 shows the results.

[0056]

[Table 3]

In Comparative Example 5, the surface roughness Ra of the recording surface was 0.6.
This is a magnetic disk using a glass substrate a having a thickness of 10 nm, and the yield of the magnetic disk is reduced as the flying height of the magnetic head is reduced.

The yield at each flying height of each magnetic head was as very low as 24% or less. At a flying height of 9 nm, no good product was obtained out of 100 sheets. In Comparative Example 6, a glass substrate a having a smaller recording surface roughness Ra of 0.3 nm was used.
The average number of foreign substances on the glass substrate was almost the same as Ra 0.6 nm, and the yield of the magnetic disk at each magnetic head flying height was similar to that of Comparative Example 5. However, the yield at each magnetic head flying height was somewhat better because the average number of foreign particles was slightly smaller than in Comparative Example 5.

On the other hand, the surface roughness Ra of the recording surface is equal to 0.1.
In the ninth embodiment using the 6 nm glass substrate E, the yield of the magnetic disk at the magnetic head flying height of 19 nm was 74%.
%, The yield at 16 nm is 60%, the yield at 12 nm is 46%, and the yield at 9 nm is 30%. The yield of the magnetic disk decreases as the flying height of the magnetic head decreases, but the yield at each flying height of the magnetic head is:
It was significantly higher than Comparative Examples 5 and 6.

This is because the glass substrate E having an extremely small average number of foreign substances was used as compared with the glass substrate a used in the comparative example.

The surface roughness Ra of the glass substrate E is 0.6 nm.
In Example 10 where the average number of foreign substances on the glass substrate was slightly reduced, the yield at each magnetic head flying height was improved. Although the yield tends to decrease as the magnetic head flying height decreases,
The effect of reducing the surface roughness Ra was obtained.

In the eleventh embodiment in which the glass substrate G having a small specific resistance was used while maintaining the surface roughness Ra at 0.6 nm, almost the same yield as in the tenth embodiment was obtained. In Example 12 in which the surface roughness Ra of the glass substrate G was reduced to 0.3 nm, the yield at each magnetic head flying height was even better than in Examples 10 and 11. Further, as in the other embodiments, the yield decreased with a decrease in the flying height of the magnetic head, but the decrease was very small as compared with the other examples.

Therefore, in order to increase the capacity of a magnetic recording apparatus by lowering the flying height of a magnetic head, a glass substrate to which a magnetic disk is applied must have a low specific resistance, and then have a high degree of cleanliness (a small number of foreign substances). Then, the surface roughness Ra of the information recording surface is small.

This example shows that a glass substrate having a specific resistance of 10 ⁹ Ω · cm or less and a surface roughness Ra of the information recording surface of 0.6 nm or less is effective.

Although the degree of cleanliness varies depending on the method of cleaning the glass substrate, the glass substrate having a lower specific resistance can be improved in cleanliness, and has the advantage that less reattachment of dust and the like occurs.

Embodiment 13 A magnetic disk which passed the magnetic head flying height of 19 nm in Examples 9 and 11 of Table 3 was mounted on a 2.5-inch magnetic recording apparatus.

FIG. 3 is a schematic view of the magnetic recording apparatus manufactured in this embodiment. The magnetic disk 7 is supported by a rotating shaft 8, and at the same time, the magnetic disk 7 is rotated by the rotation of a spindle motor 9.

The magnetic head 10 is supported by a magnetic head rotating shaft 11.
The position of the magnetic disk in the radial direction is determined by the rotation of. In addition, 12 is an output terminal of an electric system, 1
3 is a spacer.

In this embodiment, two magnetic disks 7 are mounted via the spacer 13 and a total of four magnetic heads are arranged on both surfaces of each disk. As the spacer 13, a conventional metal (stainless) material was used.

The flying height of the magnetic head 10 can be controlled to two types, 23 nm and 19 nm, by adjusting the shape of the magnetic head slider and the spring strength of the arm supporting the magnetic head. The rotation speed of the magnetic disk is 5,500 rpm
And

The manufactured magnetic recording apparatus was operated continuously for 100 hours, and the presence or absence of an error was examined. Further, by removing the magnetic disk from the magnetic recording device and observing the surface of the magnetic disk in detail, the presence / absence of damage such as film peeling and the state of any damaged part were examined.

In this embodiment in which the flying height of the magnetic head was 23 nm, the flying height of the magnetic head was 1 in Examples 9 and 11 in Table 3.
No matter which magnetic disk passed 9nm,
No error or damage to the magnetic disk was observed.

Further, even when the flying height of the magnetic head was set to 19 nm, the above problem was not observed. That is,
With the magnetic disk of the present invention, it is possible to provide a magnetic recording device compatible with a low flying height of 23 nm or less. This is highly effective in increasing the capacity of the magnetic recording device.

Since the magnetic disk of the present invention can be manufactured with a high yield, the mass productivity of the magnetic recording device can be improved. According to the present invention, it is possible to obtain a magnetic recording device that achieves both high capacity and high yield.

[Embodiment 14] As shown in FIG. 3, the same procedure as in Embodiment 13 was performed using three types of magnetic disks, each of which passed head flying heights of 16 nm, 12 nm, and 9 nm in Embodiment 12 of Table 3, and was shown in FIG. An inch magnetic recording device was manufactured. However, in this embodiment, the magnetic disk is connected to the
A total of ten magnetic heads were arranged on both sides of each disk.

As the spacer, a material having the same composition as the glass substrate G used in Example 12 was used instead of the conventional metal (stainless) spacer.

The flying height of the magnetic head is 16 nm, 1
It was made possible to control three types of 2 nm and 9 nm.
The rotation speed of the magnetic disk was 8,000 rpm. A magnetic recording device manufactured in the same manner as in
The operation was continued for 0 hours, and the presence or absence of an error and the damage of the magnetic disk were examined.

When the flying height of the head of the magnetic recording apparatus is reduced, the C / N of the read signal can be sufficiently obtained, the magnetic characteristics are improved, and the capacity can be increased. However, the low flying height of the magnetic head causes collision with the magnetic disk,
It leads to damage of the magnetic disk. This damage causes an error in the magnetic recording apparatus, and causes a serious problem that recorded information is lost.

In this example, no error was generated or the magnetic disk was not damaged even when the head flying height was significantly reduced, and the effectiveness of the magnetic disk of the present invention was confirmed.

Further, since a spacer having the same composition as the glass substrate mounted on the magnetic disk was used as the spacer,
Excellent in thermal expansion matching due to heat generated during rotation, and no reading error of the magnetic head occurred.

Usually, a conductive substance such as a metal is used as the spacer, and the material of the glass substrate according to the present invention is as follows.
It has been found that since the electric resistance (specific resistance) is small, it can be effectively used as a spacer.

Further, even if the spacer is not made of the same material as that of the glass substrate according to the present invention, the specific resistance is small to some extent.
In addition, it was confirmed that similar effects can be obtained even with similar materials having good thermal expansion matching. Here, the term “similar material” refers to a material having the same kind of component but a different component ratio from the glass substrate. Further, a material whose specific resistance and coefficient of thermal expansion match those of the glass substrate may be used.

As described above, in the magnetic disk of the present invention,
It is possible to provide a magnetic recording apparatus which is more suitable for lower flying height than the thirteenth embodiment and can cope with an increase in capacity. Further, since the magnetic disk of the present invention can be manufactured with a high yield, the mass productivity of the magnetic recording device can be improved.

In the above embodiment of the present invention, a 2.5 inch glass substrate, a magnetic disk and a magnetic recording apparatus have been described. However, the present invention can be applied to 1 inch, 3 inch, 3.5 inch or other sizes. It is a technology that can be done.

[0085]

According to the present invention, the specific resistance is 10 ¹¹ Ω · c.
m or less, preferably 10 ⁹ Ω · cm or less, and using a glass substrate having a surface roughness Ra of the information recording surface of 0.6 nm or less for the magnetic disk, the adhesion of foreign matter to the information recording surface can be significantly reduced. As a result, it is possible to manufacture a magnetic disk capable of coping with a low flying height of the magnetic head with a high yield.

Further, it is possible to provide a magnetic recording apparatus which achieves both high capacity and high yield by using the magnetic disk of the present invention.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the specific resistance of a glass substrate and the average number of foreign substances.

FIG. 2 is a schematic sectional view of a magnetic disk of the present invention.

FIG. 3 is a schematic diagram of a magnetic recording device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Precoat film, 3 ... Base film, 4 ...
Magnetic film, 5: protective film, 6: lubricant, 7: magnetic disk,
8: magnetic disk rotating shaft, 9: spindle motor, 10
... A magnetic head, 11 a head rotating shaft, 12 an electric signal output terminal, and 13 a spacer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroki Yamamoto 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Takashi Naito 7-1, Omikamachi, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi, Ltd.Hitachi Laboratory (72) Inventor Yuzo Kozono 1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Laboratory (72) Inventor Akira Kato Kozu, Kodawara City, Kanagawa Prefecture No. 2880 Storage Systems Division, Hitachi, Ltd. (72) Inventor Noriyuki Takeo No. 2880 Kokutsu, Odawara-shi, Kanagawa Prefecture F-Terms, Storage Systems Division, Hitachi, Ltd.F-term 4G059 AA00 5D006 CB04 CB06 CB07 DA03 DA04 FA00 5G067 AA52 CA01

Claims (11)

[Claims] 1. A magnetic disk having a glass substrate and an information recording thin film formed directly or via another layer on the surface of the substrate, wherein the glass substrate has a conductive material dispersed in a glass matrix. Is a magnetic disk wherein the glass substrate is dispersed in such an amount that the specific resistance at room temperature becomes 10 ¹¹ Ω · cm or less. 2. The glass substrate has a specific resistance of 10 ⁹ Ω · c.
2. The magnetic disk according to claim 1, wherein m is equal to or less than m. 3. The magnetic disk according to claim 1, wherein the conductive material is conductive fine particles. 4. The magnetic disk according to claim 3, wherein the conductive fine particles are a metal or a noble metal. 5. The method according to claim 1, wherein the conductive material is a metal ion.
Or a magnetic disk according to item 2. 6. The magnetic disk according to claim 5, wherein the metal ion is a transition metal ion. 7. The method according to claim 1, wherein the metal ions are Nb, Ti, Sn, C
6. The magnetic disk according to claim 5, wherein at least one of o, Fe, and V is used. 8. A surface roughness R of an information recording surface of a magnetic disk.
a is not more than 0.6 nm;
8. The magnetic disk according to any one of 7. 9. A magnetic recording apparatus comprising: a magnetic disk, a magnetic head, a rotating unit for rotating the magnetic disk, and a moving unit for moving the magnetic head in parallel to the surface of the magnetic disk, wherein the magnetic disk comprises a glass substrate, Having an information recording thin film formed directly or via another layer on the substrate surface,
The glass substrate has an information recording thin film formed directly or via another layer on the surface of the substrate, and a conductive material is dispersed in a glass matrix.
0 ¹¹ Ω · cm or less, and the surface roughness R of the information recording surface
a is not more than 0.6 nm, and the average flying height of the magnetic head with respect to the magnetic disk surface when recording and reproducing information on and from the magnetic disk is not more than 23 nm. 10. The glass substrate has a specific resistance of 1 at room temperature.
0 magnetic recording apparatus according to claim 9 or less ⁹ Omega · cm. 11. The magnetic recording apparatus in which two or more magnetic disks are mounted, and a spacer provided between the magnetic disks is a glass spacer having the same composition or the same constituent as the glass substrate but having a different component ratio. Claim 9 or 10
3. The magnetic recording device according to claim 1.