JP2984199B2 - Magnetic disk substrate holding member and magnetic disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holding member such as a spacer, a shim or a clamp for holding a magnetic disk substrate at a predetermined position, and a magnetic disk having a glass magnetic disk substrate held by these holding members. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, in a magnetic disk drive, a plurality of magnetic disk substrates 15 and spacers 11 are alternately inserted into a hub 14 fixed to a rotating shaft 13, and finally a shim is provided. 10 and clamp 12
It was fixed by tightening with the screw 16. The magnetic head 17 moves on the surface of the magnetic disk substrate 15 in a non-contact state while rotating the magnetic disk substrate 15 by the rotation of the rotation shaft 13, so that information can be written at a predetermined position on the magnetic disk substrate 15. And read.

In recent years, with the increase in the density and capacity of information in such a magnetic disk device 50, the distance between the magnetic head 17 and the magnetic disk substrate 15 has been minimized, and Therefore, there has been a demand for a magnetic disk substrate 15 using glass that can obtain a magnetic disk substrate 15 with extremely effective surface strength and smooth surface. The holding members such as the spacer 11, the shim 10, and the clamp 12 for fixing and holding the magnetic disk substrate 15 are used to prevent the magnetic disk substrate 15 from being distorted due to a difference in thermal expansion.
Some were formed of ceramics or glass (Japanese Patent Publication No. 5-80745, Japanese Patent Application Laid-Open No. 61-148667).

However, since ceramics and glass constituting the holding member are generally insulating materials,
It has been known in recent years that when the magnetic disk substrate 15 is held by these holding members, the magnetic disk substrate 15 is charged, and noise may be generated at the time of reading or writing information, thereby destroying recorded contents. Therefore, a holding member in which a metal film such as aluminum or zinc is coated on a contact surface with the magnetic disk substrate 15 or a holding member made of conductive ceramics in which a conductive material is added to alumina or the like is used. In some cases, the magnetic disk substrate 15 is prevented from being charged (JP-A-2-226566).

[0005]

However, in the case of a holding member having a contact surface coated with a metal film, the difference in thermal expansion between the ceramic or glass forming the base and the metal film is large.
There is a problem that the flatness of the contact surface is impaired. Therefore, when the magnetic disk device 50 is configured using this holding member, the magnetic disk substrate 15 is distorted, and the parallelism between the magnetic disk substrates 15 is impaired, so that the flying height of the magnetic head 17 is reduced. In some cases, the magnetic head 17 may come into contact with the magnetic disk substrate 15 to cause damage.

In addition, there is a risk that the coated metal film may be peeled off due to a difference in thermal expansion between the ceramic and glass, and there is another problem that static electricity charged on the magnetic disk substrate 15 cannot be released.

The metal film is coated in a thin film so as not to impair the flatness of the contact surface. However, the metal film slightly slides between the magnetic disk substrate 15 and the holding member with high-speed rotation. Since the metal film having low hardness is worn out or peeled off due to the movement, there is a fear that static electricity charged on the magnetic disk substrate 15 cannot be released.

On the other hand, the holding member made of conductive ceramic has a thermal expansion difference of about 2 to 5 × 10 ⁻⁶ / ° C. with the magnetic disk substrate 15 made of glass. There is a problem that distortion occurs and the parallelism between the magnetic disk substrates 15 is impaired.

In the magnetic disk device 50 which is required to have a higher density and a larger capacity, the device 50 using the above-mentioned holding member has not been able to obtain a satisfactory device 50 yet.

[0010]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a magnetic disk substrate holding member such as a shim, a spacer, and a clamp, in which a MgFe ₂ O ₃ and / or Fe ₃ O ₄ crystal is provided. And formed of a forsterite ceramic having a volume resistivity of less than 10 ⁷ Ω · cm.

Further, according to the present invention, a magnetic disk device is constituted by sequentially inserting and fixing the holding member and a magnetic disk substrate made of glass into a hub made of a conductive material.

[0012]

Embodiments of the present invention will be described below.

1 to 3 are views showing a holding member according to the present invention. FIG. 1A is a perspective view of a spacer 11, and FIG.
2 is a cross-sectional view thereof, FIG. 2A is a perspective view of the shim 10, and FIG.
Is a sectional view thereof, FIG. 3A is a perspective view of a clamp 12 ′,
(B) is a sectional view thereof. First, a spacer 11 shown in FIG. 1 is a ring body 112 made of a forsterite ceramic having conductivity having a volume resistivity of less than 10 ⁷ Ω · cm, and has inner and outer edge portions 113a, 1a.
A C-plane or an R-plane is formed on 13b to prevent chipping.

The contact surface 113 has a center line average roughness (Ra) of 0.2 to 2.0 μm in order to prevent the fixed magnetic disk substrate from rotating with high-speed rotation. In addition, the flatness of the contact surface 113 is set to 3 μm or less in order to prevent the magnetic disk substrate from being distorted when fixed, and the upper and lower contact surfaces are used to hold the magnetic disk substrate at a predetermined interval. The parallelism of 113 is set to 5 μm or less. As shown in FIG. 2, the shim 10 has the same shape as the spacer 11 and is slightly thinner.

The clamp 12 'shown in FIG. 3 is a disk-shaped plate-shaped body 122' made of forsterite ceramics having a conductivity of less than 10 ⁷ Ω · cm. The contact surface 123 'is the spacer 1
In order to prevent the magnetic disk substrate from being distorted and prevent the disk from rotating, the center line average roughness (R
In a), the surface roughness is set to 0.2 to 2.0 μm, and the flatness is set to 3 μm or less. In the center of the contact surface 123 ', there is provided a concave portion 124' for engaging with the tip of the hub and a screw hole 125 'for fixing to the hub. C and R surfaces are formed on a and 123'b.

[0016] Thus, the present invention is shim 10, spacers 11, and 10 ⁷ holding member such as a clamp 12 '
By forming the forsterite ceramic having a volume resistivity of less than Ω · cm, static electricity charged on the magnetic disk substrate can be efficiently released.
In addition, the forsterite ceramic constituting the holding member has the same or similar thermal expansion coefficient (8.0 to 10.0 × 10 ⁻⁶ / ° C.) as that of the magnetic disk substrate made of glass. The accompanying distortion of the magnetic disk substrate can be prevented, and the magnetic disk substrate can be held with extremely high accuracy.

Next, FIG. 4 shows a magnetic disk device 50 in which a glass magnetic disk substrate 15 having a magnetic film on the surface is held by the holding member.

A hub 14 having a substantially cylindrical body made of metal and having a flange 14a is fixed to the rotating shaft 13. A magnetic disk substrate 15 and the spacer 11 shown in FIG. Insert multiple pieces alternately, and finally Figure 2
After inserting the shim 10 shown in (1), press down with the clamp 12 made of metal or ceramics such as alumina,
The magnetic disk substrate 15 is fixed by fastening the clamp 12 to the hub 14 with screws 16.

The magnetic disk drive 50 according to the present invention comprises a magnetic disk substrate 15 and a holding member (spacer 11, shim 1).
Since the thermal expansion coefficients of 0) are the same or close to each other, there is no inconvenience caused by the difference in thermal expansion even when the temperature becomes high during high-speed rotation. Therefore, the flying height of the magnetic head 17 with respect to the magnetic disk substrate 15 can be extremely reduced, and the information recording density can be increased. In addition, since the holding members (spacers 11 and shims 10) have conductivity, static electricity charged on the magnetic disk substrate 15 can be released via the metal hub 14 and the rotating shaft 13, and the recorded contents can be recorded. Can be prevented from being destroyed.

In addition to the glass substrate, the magnetic disk substrate 15 may be a ceramic substrate in which a glass glaze layer is formed on the surface and a magnetic film is coated thereon.

In the magnetic disk drive 50 shown in FIG. 4, the shim 10 is held between the uppermost magnetic disk substrate 15 and the clamp 12, but as another embodiment, the clamp 12 is held at the uppermost position. The magnetic disk substrate 15 may be held in direct contact with the magnetic disk substrate 15. In this case, the use of the clamp 12 ′ shown in FIG. The static electricity charged on the magnetic disk substrate 15 can be effectively released.

Further, as another example of the magnetic disk device 50, the magnetic disk device 50 may be one in which the spacer 11 disposed between the flange portion 14a of the hub 14 and the magnetic disk substrate 15 is removed and held directly in contact with the magnetic disk device 50. In order to eliminate the difference in thermal expansion from the magnetic disk substrate 15, the hub 14 is also preferably formed of conductive ceramics, particularly conductive forsterite ceramics.

By the way, the spacer 11, the shim 10,
The conductive forsterite ceramic constituting the holding member such as the clamp 12 'and the like has forsterite (2MgO.SiO ₂ ) as a main component and a metal compound added as a conductive material. It is preferable to add iron-based compounds such as iron oxide (FeO, Fe ₂ O ₃ ), triiron tetroxide (Fe ₃ O ₄ ), and iron oxide hydroxide (FeO (OH)).

That is, the present inventors have conducted intensive studies on a material having a volume resistivity of less than 10 ⁷ Ω · cm, and having the same or similar thermal expansion coefficient as that of the magnetic disk substrate 15 made of glass. As a result of the superposition, if iron compounds such as iron oxide, triiron tetroxide, and iron oxide hydroxide are added to forsterite within a certain range, it can be made conductive without substantially impairing the mechanical properties. Was found. Moreover, in the forsterite-based ceramics containing an iron-based compound, chipping is less likely to occur than in the insulating forsterite-based ceramics, and the edge portions (103a, 103b, 113a, 113b, 123 ').
a, 123'b) The C-plane or R-plane amount can be reduced. Therefore, the contact area ratio of the contact surfaces (103, 113, 123 ') with the magnetic disk substrate 15 can be increased, and the distortion of the magnetic disk substrate 15 can be suppressed.

It is preferable that the iron-based compound be added in a preferable amount in the range of 20 to 60% by weight based on the whole. This is because if the addition amount is less than 20% by weight, the volume specific resistance value becomes 10 ⁷ or more and the insulating property becomes strong, so that it becomes impossible to prevent the magnetic disk substrate 15 from being charged. If it exceeds 60% by weight, the mechanical properties (Young's modulus, bending strength) are greatly reduced, so that the flatness of the contact surfaces 103, 113, 123 'of the holding members cannot be maintained, and the thermal expansion coefficient also decreases. Therefore, the difference in thermal expansion from the magnetic disk substrate 15 made of glass increases, and the magnetic disk substrate 15 is distorted.

On the other hand, in order to manufacture the holding member according to the present invention, first, a ceramic raw material in which MgO and SiO ₂ are mixed at a ratio of 50:50 is wet-mixed and pulverized, and dried to obtain fine and MgO and SiO 2. After preparing a granule in which ₂ is uniformly dispersed, firing is performed to form ceramic particles having a crystal structure of 2MgO.SiO ₂ and / or MgSiO ₃ .

Next, iron oxide (FeO, Fe ₂ O ₃ ), triiron tetroxide (Fe ₃ O ₄ ), and iron oxide hydroxide (FeO (OH)) were added to 40 to 80% by weight of the ceramic particles. 20 to 60% by weight of at least one of them based on the whole
The mixture was added together with a binder in the range described above, kneaded and dried, and then formed into a ring-shaped or disk-shaped formed body having a desired shape by a mechanical press.
By firing at a firing temperature of 00 ° C. for 1 to 2 hours, the holding member according to the present invention can be obtained.

The ceramic thus obtained is
It is preferable that crystals of 2MgO.SiO ₂ and / or MgSiO ₃ exist as the forsterite component, and at least one crystal of MgFe ₂ O ₃ or Fe ₃ O ₄ exists as the iron-based compound component. The presence of these crystals means that the peaks of the respective crystals are present by analysis by X-ray diffraction.

In the above forsterite ceramics, Ti is contained in an amount of 15% by weight or less based on the whole.
It may contain impurities such as O ₂ and CaO.

The holding member made of conductive forsteritic ceramic obtained in this manner has a volume resistivity of less than 10 ⁷ Ω · cm and a coefficient of thermal expansion of 9 to 1.
In the range of 1 × 10 ⁻⁶ / ° C. and a Young's modulus of 100 to 1
It has a flexural strength of 40 to 14 kg / mm ² .

As described above, the holding member according to the present invention can have the same or similar thermal expansion coefficient as that of the magnetic disk substrate, and has conductivity, so that the holding member has high thermal expansion during high-speed rotation. Inconvenience due to the difference in expansion does not occur, and static electricity charged on the magnetic disk substrate 15 can be released. In addition, if the magnetic disk drive according to the present invention, in which the glass magnetic disk substrate is held by using the above-mentioned holding member, is used, the flying height of the magnetic head 17 with respect to the magnetic disk substrate can be extremely reduced, and high-density recording can be performed. And the destruction of recorded contents due to the electrification of the magnetic disk substrate 15 can be prevented.

(Experimental Example) Here, among the forsterites constituting the holding member according to the present invention, iron-based compounds (iron oxide (FeO, Fe ₂ O ₃ ), triiron tetroxide (Fe
Volume resistivity when the amount of ₃ O ₄ )) is changed,
The Young's modulus, bending strength, and coefficient of thermal expansion were measured.

The evaluation criterion in this experiment is that the volume specific resistance required for the holding member is 10 ⁷ Ω · cm.
Less, Young's modulus 100 GPa or more, bending strength 10 kg / mm ²
Those having a coefficient of thermal expansion in the range of 9 to 11 × 10 ^-6 / ° C.

The results are as shown in Tables 1 to 3.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

As a result, in Samples 1, 2, 11, and 21, the amount of the iron-based compound (iron oxide (FeO, Fe ₂ O ₃ ), triiron tetroxide (Fe ₃ O ₄ )) was less than 20% by weight. For this reason, the holding member could not have the necessary conductivity when the volume specific resistance was 10 ⁷ Ω · cm or more.

In samples 9 and 18, iron compounds (iron oxide (FeO, Fe ₂ O ₃ ), triiron tetroxide (Fe
_Since the added amount of ₃ O ₄ )) was more than 60% by weight, the volume resistivity was less than 10 ⁷ Ω · cm, but the Young's modulus, bending strength, and thermal expansion coefficient did not satisfy the reference values.

On the other hand, Samples 3 to 8,1 according to the present invention
2 to 17, 22 to 27 are iron compounds (iron oxide (Fe
O, Fe ₂ O ₃ ) and triiron tetroxide (Fe ₃ O ₄ )) are in the range of 20 to 60% by weight, so that the volume resistivity is less than 10 ⁷ Ω · cm, the Young's modulus is 100 GPa or more, Flexural strength of 10 kg / mm ² or more and thermal expansion coefficient of 9-11 ×
It was in the range of 10 ⁻⁶ / ° C., and the standard value could be satisfied.

[0041]

As described above, according to the present invention, the shim,
A holding member for a magnetic disk substrate such as a spacer and a clamp is internally provided with MgFe ₂ O ₃ and / or Fe ₃
Since it is made of a forsterite ceramic having an O ₄ crystal and having a volume resistivity of less than 10 ⁷ Ω · cm, the coefficient of thermal expansion can be made equal to or close to the coefficient of thermal expansion of the magnetic disk substrate. However, there is no inconvenience caused by the difference in thermal expansion, and static electricity charged on the magnetic disk substrate can be efficiently released.

Further, according to the present invention, a magnetic disk drive is constructed by sequentially inserting and fixing a glass magnetic disk substrate to a hub made of a conductive material using the above-mentioned holding member, thereby providing a magnetic head with respect to the magnetic disk substrate. The flying height can be made extremely small, and high-density recording (large capacity) can be realized, and static electricity charged on the magnetic disk substrate can be efficiently released through the holding member and the hub. Can be prevented.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing a spacer which is an example of a holding member according to the present invention, wherein FIG. 1A is a perspective view and FIG.

FIGS. 2A and 2B are views showing a shim as an example of a holding member according to the present invention, wherein FIG. 2A is a perspective view and FIG.

3A and 3B are views showing a clamp as an example of a holding member according to the present invention, wherein FIG. 3A is a perspective view and FIG. 3B is a cross-sectional view.

FIG. 4 is a longitudinal sectional view showing a magnetic disk drive according to the present invention.

[Explanation of symbols]

 10: Shim 102: Ring body 103: Contact surface 11: Spacer 112: Ring body 113: Contact surface 12 ': Clamp 122': Plate 123 ': Contact surface 13: Rotating shaft 14: Hub 15: Magnetic Disk substrate 17: Magnetic head

Claims (2)

(57) [Claims] A holding member for holding a magnetic disk substrate made of glass at a predetermined position has MgFe ₂ O ₃ and / or
Or a volume resistivity value having Fe ₃ O ₄ crystal of 10 ⁷
Holding member for a magnetic disk substrate characterized by being formed by off Orusuteraito ceramics under Omega · cm. 2. A hub made of a conductive material, a magnetic disk substrate made of glass, MgFe ₂ O ₃ and / or Fe
Volume resistivity value having a crystal of ₃ O ₄ is 10 ⁷ Ω · cm
Magnetic disk apparatus characterized by sequentially inserted and fixed a less than full Orusuteraito ceramics or Ranaru magnetic disc substrate holding member.