JPH08315533A - Holding member for magnetic disc substrate and magnetic disc employing it - Google Patents

Abstract

PURPOSE: To protect the edge part against chipping and to minimize the fly height of magnetic head by forming a holding member of a specified material, setting a predetermined actual touching area with a board and a predetermined flatness on the touching surface. CONSTITUTION: A spacer 20 is a ring body 21 made of ceramics or glass and a chamfered C face is formed by firing at the inner edge parts 23a, 23b in order to protect the inner edge parts 23a, 23b against chipping. The arithmetical mean deviation of abutting face 22 is set in the range of 0.2-2.0μm in order to prevent turning of a magnetic disc board fixed thereto accompanying high speed rotation. At the same time, the rate of area actually abutting on the magnetic disc board is set in the range of 50-90% and the flatness of abutting face 22 is set at 3μm or less in order to protect the magnetic disc board against strain at the time of clamping. Furthermore, the parallelism between upper and lower abutting faces 22 is set at 5μm or less in order to keep a predetermined interval of magnetic disc board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device used as an external storage device of a computer and a magnetic disk substrate holding member used for the magnetic disk device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, in a magnetic disk device, a plurality of magnetic disk substrates 12 and spacers 20 are alternately inserted into a hub 11 fixed to a rotary shaft 10, and finally a shim is inserted. 30 and clamp 40,
It is fixed by tightening with a screw 13. Then, while the magnetic disk substrate 12 is rotated by the rotation of the rotating shaft 10, the magnetic head 14 moves on the surface of the magnetic disk substrate 12 in a non-contact state, thereby writing information at a predetermined position on the magnetic disk substrate 12. I was supposed to read.

In recent years, such a magnetic disk device 50 is required to make the distance between the magnetic head 14 and the magnetic disk substrate 12 extremely small as the information density increases. The magnetic disk substrate 12 is made of ceramics or glass that has high rigidity and does not easily deform, and the holding members such as the spacers 20, the shims 30, and the clamps 40 that fix the magnetic disk substrate 12 are magnetic due to the difference in thermal expansion. In order to prevent the disk substrate 12 from being deformed, there has been one formed of the same ceramic or glass as the magnetic disk substrate 12 (Japanese Patent Publication No. 5-80745, Japanese Patent Laid-Open No. 61-148667).
Issue).

For example, the spacer 20 for holding the magnetic disk substrate 12 at a predetermined interval was made of alumina ceramics and formed on the ring body 21 as shown in FIG.

On the other hand, in Japanese Patent Application Laid-Open No. 51-118408, a plurality of air grooves are radially formed on the contact surface with the magnetic disk substrate 12 in order to relieve the stress applied to the magnetic disk substrate 12 during clamping. However, a holding member such as a spacer or a shim configured to form an air layer in the air groove is also disclosed.

[0006]

However, since the ceramics or glass forming the holding member such as the spacer 20, the shim 30, and the clamp 40 is a brittle material, the edge portion is chipped due to the stress during clamping. I was afraid. If the fragments enter the gap between the magnetic disk substrate 12 and the magnetic head 14 floating above the magnetic disk substrate 12, the magnetic disk substrate 12 may be scratched or the magnetic head 14 may be damaged.

On the other hand, at the time of clamping, the magnetic disk substrate 12
In order to relieve the stress applied to the holding member, an air groove is formed on the contact surface, and an air layer is formed on the air groove.
If the ratio of the air grooves to the contact surface is large, the contact area with the magnetic disk substrate 12 becomes too small, which may cause distortion in the magnetic disk substrate 12. Therefore, the flatness of the magnetic disk substrate 12 at the time of clamping cannot be reduced, and the flying height of the magnetic head 14 cannot be made minute. In particular, when the magnetic disk substrate 12 is distorted in a V shape, the magnetic head 14 collides with the magnetic disk substrate 12 and is damaged.

In recent years, it has been known that static electricity is charged on the magnetic disk substrate 12 at the time of reading and writing information, which may cause noise and destroy recorded contents. Since it is generally an insulating material, it was not possible to prevent the magnetic disk substrate 12 from being charged.

[0009]

In view of the above problems, the present invention forms holding members such as shims, clamps, and spacers from ceramics or glass, and has an actual contact area ratio with a magnetic disk substrate of 50. ~ 95
%, And the flatness of the contact surface is 3 μm or less.

Further, according to the present invention, one or a plurality of magnetic disk substrates are arranged on a hub having a substantially cylindrical shape which is fixed to a rotating shaft through a ring-shaped spacer and a shim, and the magnetic disk substrates are held by a clamp. In the disk device, the magnetic disk substrate is made of ceramics or glass, and the actual contact area ratio with the magnetic disk substrate is 50 to 95%.
In addition, the magnetic disk device is constituted by holding the contact surface with a spacer and a shim having a flatness of 3 μm or less.

Further, according to the present invention, a vertical through hole is formed in the contact surface of the holding member such as the shim or clamp, and a spring is provided inside the through hole, or the through hole is electrically conductive. A magnetic material is filled or coated on the surface of the magnetic material so as to establish continuity between the upper and lower contact surfaces to prevent the magnetic disk substrate from being charged.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

1A and 1B are perspective views showing a holding member according to the present invention, wherein FIG. 1A is a spacer, and FIG.
Is a clamp.

First, as shown in FIG. 1A, the spacer 20 is a ring body 21 made of ceramics or glass.
In order to prevent chipping, the inner and outer edge portions 23a and 23b have chamfered C faces as they are baked.

The contact surface 22 has a center line average roughness (Ra) of 0.2 to 2.0 .mu.m so that the fixed magnetic disk substrate does not rotate with high speed rotation. The flatness of the contact surface 22 is set to 3 μm or less to prevent the magnetic disk substrate from being distorted when clamped, and the upper and lower contact surfaces 22 are used to hold the magnetic disk substrate at a predetermined interval. Has a parallelism of 5 μm or less.

Although the shim 30 is not shown, it has the same shape as the spacer 20 and is slightly thin.

Next, as shown in FIG. 1B, the clamp 40 is a disk-shaped plate 41 made of ceramics or glass, and its abutting surface 42 is the same as the spacer 20 in the magnetic disk. In order to prevent the substrate from distorting and prevent it from rotating, the center line average roughness (R
In a), the surface roughness is 0.2 to 2.0 μm, and the flatness is 3 μm or less. In addition, a concave portion 44 that engages with the tip portion of the hub is provided at the center of the contact surface 42,
An edge portion 43a of the recessed portion 44 and an outer peripheral edge portion 43b of the plate-like body 41 have chamfered portions which are C-planes as they are baked.

The spacer 20, shim 30, and
As another example of the holding member such as the clamp 40, a through hole or a groove may be provided.

For example, the spacer 20 shown in FIG.
Has four through holes 22a formed in the contact surface 22,
With such a structure, the weight of the spacer 20 can be reduced. If the spacer 20 is used to hold the magnetic disk substrate 12, the weight applied to the rotating shaft 10 can be significantly reduced, and therefore the magnetic disk substrate 12 can be rotated at high speed with a small torque. In addition, at least two or more through holes 22a formed in the contact surface 22 may be formed at equal intervals.

Further, the spacer 20 shown in FIG.
As with the spacer 20 shown in FIG.
The two through holes 22a are bored, and the through holes 22a are provided with springs 25 made of a conductive material such as metal so that both ends thereof slightly project from the contact surfaces 22. Therefore, if the spacer 20 is used to hold the magnetic disk substrate 12, both ends of the spring 25 can be housed in the through holes 22a by the elastic action, so that the magnetic disk substrate 12 is not deformed. Since both ends of the spring 25 are in contact with the magnetic disk substrate 12 arranged on the upper and lower abutting surfaces 22 of the spacer 20, static electricity charged on the magnetic disk substrate 12 can be released to prevent the recorded contents from being destroyed. it can.

The spring 25 is used for the magnetic disk device 50.
May be inserted into the through hole 22a of the spacer 20 at the time of assembling, and the spring 25 may be disposed in the through hole 22a and fixed by an adhesive or the like in order to improve the efficiency of the assembly work. good.

The spacer 20 shown in FIG.
Instead of 5, the through hole 22a is filled with a conductive material 26 so that the upper and lower contact surfaces 22 can be electrically connected. The entire surface of the conductive material 26 is the contact surface 22.
Does not have to be on the same plane as that of the above, but a part thereof may be on the same plane as the upper and lower contact surfaces 22. The conductive material 26
For this, a metal such as aluminum, zinc, or carbon, or a resin having conductivity may be used.

Further, the spacer 20 shown in FIG.
The inner wall surface of the through hole 22a is coated with a conductive film 27, which is lightweight and allows the upper and lower contact surfaces 22 to be electrically connected. The edge portion of the through hole 22a is chamfered such as a C surface, and the C surface is also covered with the conductive film 27.

Therefore, even if the spacer 20 shown in FIGS. 2C and 2D is used, the static electricity charged on the magnetic disk substrate 12 can be released.

Further, like the spacer 20 shown in FIG. 2 (e), a plurality of air grooves 22b are provided on the upper and lower contact surfaces 22, respectively.
Is formed in a radial shape. With such a structure, not only the weight of the spacer 20 is reduced, but also by forming an air layer in the air groove 22b, the stress applied to the magnetic disk substrate 12 at the time of clamping is reduced. Can be alleviated to reduce the distortion generated in the magnetic disk substrate 12.

Next, these spacers 20, shims 30,
A magnetic disk device 50 holding the magnetic disk substrate 12 by the clamp 40 is shown in FIG.

A hub 11 having a substantially cylindrical metal body 15 having a flange portion 11a is fixed to the rotary shaft 10, and the hub 1 is fixed.
A plurality of magnetic disk substrates 12 on the flange portion 11a of
And the spacer 20 are alternately inserted, and finally, the shim 30 and the clamp 40 hold the magnetic disk substrate 12 between the flange portion 11a of the hub 11 and the clamp 40, and the spacer 20 (the shim 30) is used. The magnetic disk substrate 12 is held at a predetermined interval,
Further, the magnetic disk substrate 12 is fixed by fastening the clamp 40 to the hub 11 with the screw 13. Then, while the magnetic disk substrate 12 is rotated at a high speed via the rotary shaft 10, the magnetic head 14 floated above the surface of the magnetic disk substrate 12 with a minute distance to write and read information. ing.

The magnetic disk substrate 12 provided in the magnetic disk device 50 is made of ceramics such as alumina or glass which is lightweight and has high rigidity and is hard to be deformed as information density is increased. In a substrate made of glass, a magnetic disk substrate 12 can be obtained by forming a glaze layer on the surface and forming a magnetic film on the glaze layer.
The magnetic disk substrate 12 can be obtained by forming a magnetic film on the surface thereof. Furthermore, titanium, silicon, YAG, carbon or the like can be used as another substrate material.

In particular, if the magnetic disk substrate 12 is held by using the holding member according to the present invention, the coefficient of thermal expansion of the magnetic disk substrate 12 can be made equal to or approximate to that of the magnetic disk substrate 12. The distortion of No. 12 can be eliminated, the flying height of the magnetic head 14 can be made extremely small, and the information recording density can be improved. In the magnetic disk device 50 shown in FIG. 3, the shim 30 is held between the uppermost magnetic disk substrate 12 and the clamp 40, but in addition to this, the clamp 40 is held on the uppermost magnetic disk substrate 12. The magnetic disk substrate 12 can be accurately held by using the clamp 40 shown in FIG. 1B in this case. In addition, the flange portion 11 of the hub 11
spacer 2 arranged between a and the magnetic disk substrate 12
It is also possible to have a structure in which 0 is removed and directly contacted and held. In this case, it is preferable that the hub 11 is also made of ceramics or glass in order to eliminate the difference in thermal expansion from the magnetic disk substrate 12.

The material forming the holding member such as the spacer 20, the shim 30, and the clamp 40 has a coefficient of thermal expansion of 20 × 10 ⁻⁶ / ° C. or less, preferably 12 × 10 ^−6.
Ceramics or glass as shown in Table 1 below / ° C. can be used.

Then, depending on the material of the magnetic disk substrate 12, a material having a thermal expansion coefficient close to that of the material of the holding member may be used. For example, in the case of using the magnetic disk substrate 12 made of ceramic, as a holding member,
It suffices to use ceramics having a coefficient of thermal expansion of 10 × 10 ⁻⁶ / ° C. or less, similarly to glass (coefficient of thermal expansion 8.0 to
When a magnetic disk substrate 12 made of (× 10 ⁻⁶ / ° C.) is used, if ceramics or glass having a thermal expansion coefficient of 8.0 × 10 ⁻⁶ / ° C. or more such as forsterite in Table 1 is used as the holding member. It is suitable.

[0032]

[Table 1]

By the way, the spacer 20, the shim 30,
And edge portions 23, 4 of the holding member such as the clamp 40
In No. 3, a chamfered portion such as a C surface, an R surface, or a tapered surface having a larger taper angle than the C surface is formed on the edge portions 23 and 43 of the holding member for the purpose of preventing chipping due to stress during clamping. However, the present invention is characterized in that the chamfered portion is a surface as it is baked. That is, if it is attempted to form a chamfered portion on the edges 23 and 43 of the fired holding member, it takes a very long time to process one holding member and microcracks are generated on the surface of the polished chamfered portion. Although there is a possibility that chipping may occur due to the stress during clamping, the chamfered part as fired as in the present invention has the original strength of the sintered body, so that the stress due to clamping causes It is possible to completely prevent chipping.

Here, the chamfered as-fired portion referred to in the present invention has a predetermined shape in advance by an ordinary molding method such as a uniaxial pressure molding method, an isobaric pressure molding method, and a cast molding method. The chamfered portion is formed and then fired, and the chamfered portion is not subjected to polishing or grinding after firing.

For example, when the C-face is formed by a uniaxial pressure forming machine such as a mechanical press, as shown in FIG. 3, the chamfered portion consisting of the tapered surface T and the flat surface H is integrally formed with the edge portions 23 and 43 of the holding member. And then fired to polish the outer peripheral surface to a predetermined size. At this time, the edge portion 2 of the holding member
The plane H is cut off at 3,43, and the C-plane portion remains. Then, the C surface becomes the chamfered portion as it is baked in the present invention. Although the flat surface H is cut off in the above example, the strength of the chamfered portion does not decrease even if the flat surface portion 2 is slightly curved or the holding member that leaves the flat surface H entirely. Will not cause any problems.

On the other hand, if the amount of chamfer formed on the holding member is large, the fixed magnetic disk substrate 12 may be greatly distorted. Further, even if the ratio of the through holes 22a and the air grooves 22b formed in the contact surfaces 22 and 42 increases, the magnetic disk substrate 12 may be distorted.

Therefore, in the present invention, the actual contact area ratio of the holding member is set in the range of 50 to 95%, preferably 70 to 95%.

The actual contact area ratio is the edge portion 2 of the holding member.
Chamfers, through holes 22a and air grooves 22b
With respect to the total area of the contact surfaces 22 and 42 before the formation of
It is the ratio of the contact surfaces 22, 42 after the chamfered portions and the through holes 22a and the air grooves 22b are formed in the edge portions 23, 43. For example, each dimension of the spacer 20 shown in FIG. When set as shown in FIG. 4, it is a value calculated by the following equation.

Formula Actual contact area ratio (%) = (R ² −S ² ).
/ (P ² −Q ² ) × 100 If the actual contact area ratio is less than 50%, the contact area with the magnetic disk substrate 12 is too small, so the magnetic disk substrate 12 is distorted during clamping, and the magnetic head This is because the flying height of the magnetic head 14 cannot be reduced, and if it becomes worse, the magnetic disk substrate 12 is distorted into a V-shape, and the magnetic head 14 is contacted and damaged due to this distortion.

The higher the actual contact area ratio, the higher the flatness of the magnetic disk substrate 12. However, if the actual contact area ratio exceeds 95%, the chamfering amount is too small. Even if the chamfered portion is provided, the chipping may occur due to the stress at the time of clamping. Therefore, it is important to set the upper limit of the actual contact area ratio to 95%, and if chamfered portions are formed in the edge portions 23 and 43 within this range, chipping will not occur due to stress during clamping.

Further, in the holding member according to the present invention, the flatness of the contact surfaces 22 and 42 is 3 μm or less in order to prevent the clamped magnetic disk substrate 12 from being distorted in the same manner as the actual contact area ratio. It is important that the thickness is preferably 1 μm or less, more preferably 0.3 μm or less.

Further, it is important that the contact surfaces 22 and 42 are appropriately rough surfaces.

That is, when the surface roughness of the contact surfaces 22 and 42 is less than 0.2 μm in the center line average roughness (Ra), the contact surface 2
This is because slippage of the magnetic disk substrate 12 rotating at a high speed cannot be prevented because 2, 42 are too smooth, and conversely, when the center line average roughness (Ra) is greater than 2.0 μm, the magnetic disk substrate 12 is greatly distorted. Occurs and flatness is 2μ
This is because the magnetic disk substrate 12 cannot be set to m or less and the magnetic disk substrate 12 may be damaged.

Therefore, it is preferable that the contact surfaces 22 and 42 have a center line average roughness (Ra) of 0.2 μm to 2.0 μm.

As described above, according to the present invention, since the holding member for holding the magnetic disk substrate 12 at a predetermined interval is made of ceramics or glass, the distortion of the magnetic disk substrate 12 due to the difference in thermal expansion is largely prevented. Since the actual contact area ratio is 50 to 95% and the flatness is 3 μm or less, no V-shaped distortion is generated on the magnetic disk substrate 12, and even if distortion is generated. Since it can be distorted smoothly, stable writing and reading of information can be performed. Moreover, since the chamfered portion formed at the edge portion of the holding member is the surface as it is baked, it is possible to completely prevent the chipping caused by the stress during clamping.

Therefore, when the magnetic disk substrate 12 is held by the holding member to form a magnetic disk device, the flatness of the magnetic disk substrate 12 can be set to 2 μm or less, and the flying height of the magnetic head is 0. It can be set to 1 μm or less, and high density recording can be realized.

Here, the actual contact area ratio of the spacers 20 was changed, and the flatness and distortion of the magnetic disk substrate 12 held by these spacers 20 were measured using an optical interferometer.

The spacer 20 used in this measurement has an outer diameter of 24.
mm, an inner diameter of 20 mm, a C-face is formed on the inner and outer edge portions 23 as the chamfered as-fired portion, and the spacer 20 is made of a ceramic material having a diameter of 20.97 mm as shown in FIG. The flatness and the degree of distortion of the magnetic disk substrate 12 with the magnetic disk substrate 12 being held were measured.

The value of the changed actual contact area ratio and the flatness at that time are as shown in Table 2, and the degree of distortion of each is as shown in FIG.

The evaluation criteria in this measurement are that the magnetic disk substrate 12 has no V-shaped distortion and the flatness is 2 μm.
The following were considered excellent:

[0051]

[Table 2]

As can be seen from Table 2, in Samples 6 and 7, since the actual contact area ratio is 40% or less, the flatness of the magnetic disk substrate 12 is greatly distorted to 2.1 to 3.9 μm.
It could not be set to 2 μm or less. Further, as can be seen from (6) and (7) of FIG. 6, a large number of elongated elliptical interference fringes are seen, and the intervals are very narrow. A local cusp was formed on the surface, and a V-shaped strain was formed.

On the other hand, in the samples 1 to 5 according to the present invention, since the actual contact area ratio is 50% or more, the flatness of the magnetic disk substrate 12 can be set to 1.5 μm or less, which is a reference value. Was able to be satisfied. Further, as can be seen from (1) to (5) of FIG. 6, the intervals of the interference fringes are large, and the interference fringes are not elliptical elliptical but draw smooth circles. There were no points.

In particular, the actual contact area ratio of Samples 1 to 3 is 70%.
In the above, since interference fringes that draw a smooth circle are seen as can be seen from (1) to (3) of FIG. 6, it can be seen that the distortion is a very smooth conical shape. Therefore, if the magnetic head 14 is levitated on the magnetic disk substrate 12, the magnetic head 14 can be always positioned at a predetermined track with a constant distance, and stable and high-density recording is possible.

Next, the spacer 2 having an actual contact area ratio of 90%
The flatness of the contact surface 22 was changed by using 0, and the displacement amount at the peripheral portion of the magnetic disk substrate 12 when held by the spacer 20 was measured. As shown in FIG. 7, when the spacer 20 having the radius r and the flatness F of the contact surface 22 is used to hold the magnetic disk substrate 12 having the radius R and the maximum bending occurs, the warp angle of the magnetic disk substrate 12 is increased. θ is represented by θ = tan ⁻¹ (2Fr / (r ² −F ² )), and when L = R−r, the magnetic disk substrate 12
The amount of displacement Δg at the peripheral portion of Δg = Ltan θ + F =
It is represented by (2Fr / (r ² −F ² )) L + F.

Here, r = 11.53 mm, L = 20.
Table 3 shows Δg when the value of the flatness F was changed to 97 mm.

[0057]

[Table 3]

As is apparent from Table 3, the flatness F is set to 3 μm or less, preferably 1 μm or less.
It turns out that can be made extremely small.

[0059]

As described above, according to the present invention, holding members such as shims, clamps, and spacers are made of ceramics or glass, and the actual contact area ratio with the magnetic disk substrate is 50 to 95%, and By setting the flatness of the contact surface to 3 μm or less, it is possible to completely prevent the chipping that occurs at the edge portion due to the stress during clamping, increase the flatness of the magnetic disk substrate, and reduce the flying height of the magnetic head. It can be quantity.

Further, according to the present invention, the recording density of information can be increased by forming the magnetic disk device by holding the magnetic disk substrate with the spacer and the shim which are the holding members. In particular, when the magnetic disk device is configured by combining the magnetic disk substrate made of ceramics or glass, the magnetic disk substrate is not distorted during clamping, and the holding member and the magnetic disk substrate have the same thermal expansion coefficient. Therefore, high-density recording of information is possible.

Further, according to the present invention, a vertical through hole is formed in the contact surface of the holding member such as the shim or clamp, and a spring made of a conductive material is arranged inside the through hole.
Since the through hole is filled with a conductive material, or the inner wall surface of the through hole is covered with a conductive film so as to establish continuity between the upper and lower contact surfaces, static electricity charged on the magnetic disk substrate is prevented. It is possible to effectively escape and prevent the recorded contents from being destroyed.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a holding member according to the present invention, in which (a) is a spacer and (b) is a clamp.

2A to 2E are perspective views showing another embodiment of the spacer according to the present invention.

FIG. 3 is a cross-sectional view showing a structure of a peripheral portion of a molded body in which the holding member according to the present invention is formed by a uniaxial pressure molding machine.

FIG. 4 is a vertical sectional view of the spacer shown in FIG.

FIG. 5 is a vertical cross-sectional view showing a magnetic disk device according to the present invention.

FIG. 6 is a photograph showing interference fringes observed on a magnetic disk substrate when the magnetic disk substrate is held by spacers having different actual contact area ratios.

FIG. 7 is a schematic diagram showing a distortion amount of a magnetic disk substrate in a magnetic disk device according to the present invention.

FIG. 8 is a perspective view showing a spacer which is an example of a conventional holding member.

[Explanation of symbols]

 10: Rotating shaft 11: Hub 12: Magnetic disk substrate 14: Magnetic head 20: Spacer 21: Ring body 22: Contact surface 23: Edge part

Claims (3)

[Claims] 1. A holding member made of ceramics or glass for holding one or a plurality of magnetic disk substrates at a predetermined interval, and the actual contact area ratio of the holding member with the magnetic disk substrate is 50 to 50. A holding member for a magnetic disk substrate having a flatness of 95% and a contact surface of 3 μm or less. 2. A magnetic disk device in which one or more magnetic disk substrates are arranged on a hub having a substantially cylindrical shape fixed to a rotary shaft via a ring-shaped spacer and / or shim and held by a clamp. In the above, the magnetic disk substrate is made of ceramics or glass, and a holding member such as a spacer or a shim having an actual contact area ratio with the magnetic disk substrate of 50 to 95% and a flatness of the contact surface of 3 μm or less. A magnetic disk device that holds it. 3. A vertical through hole is formed in the contact surface of the holding member, and a spring made of a conductive material is provided in the through hole, or the through hole is filled with a conductive material. 3. The magnetic disk according to claim 1, wherein the inner wall surface of the through hole is coated with a conductive film so that electrical conduction is established at upper and lower contact surfaces. apparatus.