JP2005050436A - Spacer for magnetic disk, and hard disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spacer for a magnetic disk, the spacer having a thermal expansion coefficient of about 8.0 to 9.5×10<SP>-6</SP>/°C. <P>SOLUTION: The spacer for the magnetic disk l includes a sintered compact containing Al<SB>2</SB>O<SB>3</SB>, TiC, and MgO, wherein the sintered compact includes 35 to 55 wt.% of MgO to the total weight of Al<SB>2</SB>O<SB>3</SB>, TiC, and MgO. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic disk spacer interposed between magnetic disks in a hard disk device (HDD) and a hard disk device using the same.

  Conventionally, a plurality of magnetic disks having a magnetic recording layer formed on a disk, a magnetic disk spacer interposed between the magnetic disks and separating the magnetic disks at a predetermined interval, a motor for rotating the magnetic disk, 2. Description of the Related Art A hard disk device (HDD) including a magnetic head that performs at least one of writing information to and reading information from a magnetic recording layer of a magnetic disk is known.

In recent years, glass materials have been used as magnetic disk substrates, and attempts have been made to use lightweight and high-strength ceramic materials as magnetic disk spacers (see Patent Document 1).
JP 2001-247357 A

However, the thermal expansion coefficient of the above-mentioned ceramic material is about 7 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the glass material that is the material of the magnetic disk substrate is 8.5 to 9.3 × 10 ⁻⁶ / ° C. There is a big difference. Therefore, when the temperature of the magnetic disk or the magnetic disk spacer in the hard disk device fluctuates within the range of −30 to 50 ° C., which is the allowable environmental temperature of the hard disk device, the degree of expansion of the magnetic disk and the magnetic disk spacer is increased. Due to the large difference, the magnetic disk may be distorted and the performance of reading / writing may be affected.

The present invention has been made in view of the above problems, and is made of a ceramic having a thermal expansion coefficient of approximately 8.0 to 9.5 × 10 ⁻⁶ / ° C., which is substantially equal to the thermal expansion coefficient of a magnetic disk made of glass. An object is to provide a spacer for a magnetic disk.

As a result of intensive studies, the inventors have added a predetermined ratio of MgO to an AlTiC material containing Al ₂ O ₃ (alumina) and TiC (silicon carbide), so that the thermal expansion coefficient is 8.0 to 9.5 × 10. The inventors have found that a ceramic material of about ⁻⁶ / ° C. can be obtained and have come to the present invention.

Spacer for a magnetic disk according to the present invention, Al ₂ O _3, TiC, and have a sintered body containing MgO, the sintered body is Al ₂ O _3, TiC, and, relative to the total weight of MgO MgO is contained in an amount of 35 to 55% by weight.

A hard disk device according to the present invention includes a plurality of magnetic disks having a magnetic recording layer formed on a glass substrate, a magnetic disk spacer interposed between the magnetic disks, a motor for rotating the magnetic disk, and a magnetic disk magnetic field. A magnetic head that performs at least one of writing information to the recording layer and reading information from the magnetic recording layer of the magnetic disk, and the spacer for the magnetic disk is a sintered body containing Al ₂ O ₃ , TiC, and MgO. The sintered body contains 35 to 55% by weight of MgO based on the total weight of Al ₂ O ₃ , TiC, and MgO.

According to the present invention, a ceramic magnetic disk spacer having a thermal expansion coefficient of about 8.0 to 9.5 × 10 ⁻⁶ / ° C. can be obtained. For this reason, the thermal expansion coefficient of the magnetic disk spacer can be made sufficiently close to the thermal expansion coefficient of the magnetic disk including the glass substrate. As a result, even if the temperature of the magnetic disk and the spacer in the hard disk device fluctuates, the rate of thermal expansion becomes approximately the same, so that unnecessary distortion or the like is less likely to occur in the magnetic disk.

Here, the sintered body, Al ₂ O _3, TiC, and, relative to the total weight of MgO, preferably contains TiC 20 to 30 wt%.

  Thus, a magnetic disk spacer having sufficient strength and sufficiently sintered can be obtained. Here, if the amount of TiC is less than 20% by weight, the rigidity tends to decrease and the strength of the spacer tends to decrease. On the other hand, if the amount of TiC exceeds 30% by weight, it becomes difficult to sinter, becomes brittle, and the strength tends to decrease again.

Further, the sintered body, Al ₂ O _3, TiC, and, relative to the total weight of MgO, preferably comprises MgO 40 to 50 wt%, thereby, 8.5-9.0 × 10 ^-6 A spacer for a magnetic disk having a thermal expansion coefficient of about / ° C. is obtained, and is more preferable.

  The outer shape of the sintered body is preferably a ring.

  According to the present invention, the reliability of the hard disk device can be improved and the recording density can be improved.

  First, a hard disk device (HDD) according to the present embodiment will be described.

  As shown in FIG. 1, the hard disk device 100 according to the present embodiment mainly includes a plurality of magnetic disks 24 having a magnetic recording layer 25 formed on a surface thereof, a spindle 70 serving as a rotation axis of the plurality of magnetic disks 24, A spacer (corresponding to a magnetic disk spacer) 10 interposed between the magnetic disks 24, a motor 20 that rotates the magnetic disk 24, and a magnetic head 18 that faces the magnetic recording layer 25 of the magnetic disk 24 are included.

  The magnetic disk 24 includes a glass material disk 23 and magnetic recording layers 25 formed on both surfaces of the disk 23. Further, the magnetic disk 24 has a through hole 24a penetrating front and back at the center.

Examples of the glass material of the magnetic disk 24 include tempered glass and chemically tempered glass, and their thermal expansion coefficient is approximately 8.5 to 9.3 × 10 ⁻⁶ / ° C. For example, examples of the tempered glass include HOYA (registered trademark) N5 glass and soda lime glass, and examples of the chemically tempered glass include HOYA (registered trademark) N10 glass. The thermal expansion coefficient of N5 glass is about 9.1 × 10 ⁻⁶ / ° C., the thermal expansion coefficient of soda lime glass is about 9.1 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of N10 glass is about 8. 7 × 10 ⁻⁶ / ° C.

  The spindle 70 has a cylindrical portion 70 a, and the outer diameter of the cylindrical portion 70 a is approximately the same as the inner diameter of the through hole 24 a of the magnetic disk 24.

  As shown in FIG. 2, the spacer 10 is a composite ceramic sintered body having an annular outer diameter. Specifically, for example, the inner diameter is about 20 mm, the outer diameter is about 24 mm, and the height is about 2 mm. The inner diameter of the spacer 10 is approximately the same as the inner diameter of the through hole 24 a of the magnetic disk 24. The material of the spacer 10 will be described later.

  The magnetic disk 24 and the spacer 10 are fitted into the columnar portion 70a of the spindle 70 so that the spacer 10 is sandwiched between the magnetic disks 24 and 24, respectively. The end of the spindle 70 is fixed by the clamp 21, and the magnetic disk 24 and the spacer 10 are fixed to the spindle 70.

  The spacer 10 maintains the interval between the magnetic disks 24 and 24 at a predetermined interval.

  The motor 20 rotates the magnetic disk 24 by rotating the spindle 70 around the axis of the spindle 70.

  The magnetic head 18 is movable in parallel to the surface of the magnetic recording layer 25 of the magnetic disk 24, records information on a desired portion of the magnetic recording layer 25, and Read information from the part.

The magnetic disk spacer 10 in this embodiment contains Al ₂ O ₃ (alumina), TiC (titanium carbide), and MgO (magnesia), and the total weight of Al ₂ O ₃ , TiC, and MgO. The composite ceramic sintered body containing 35 to 55% by weight of MgO is formed.

Such a spacer 10 has a thermal expansion coefficient of about 8.0 to 9.5 × 10 ⁻⁶ / ° C. For this reason, the thermal expansion coefficient of the spacer 10 can be made sufficiently close to the thermal expansion coefficient 8.5 to 9.3 × 10 ⁻⁶ / ° C. of the magnetic disk 24 formed mainly by the disk 23 made of glass material.

  As a result, even if the temperature of the magnetic disk 24 and the spacer 10 of the hard disk device 100 fluctuates, the rate of thermal expansion of each becomes the same, so that it is difficult to generate unnecessary distortion or the like in the magnetic disk 24.

  Therefore, when such a spacer 10 is used as the spacer 10 of the magnetic disk 24, the reliability of the hard disk device 100 can be improved and the recording density can be improved.

Here, when the content of MgO is less than 35% by weight, the thermal expansion coefficient becomes lower than 8.0 × 10 ⁻⁶ / ° C. On the other hand, when the content of MgO exceeds 55% by weight, the thermal expansion coefficient becomes higher than 9.5 × 10 ⁻⁶ / ° C.

For example, if the thermal expansion coefficient exceeds 9.5 × 10 ⁻⁶ / ° C. or falls below 8.0 × 10 ⁻⁶ / ° C., the difference in thermal expansion coefficient from the magnetic disk 24 made of glass material increases. In some cases, distortion or the like may occur in the magnetic disk 24 or the like as the temperature changes.

The thermal expansion coefficient of the spacer 10 made of a sintered body containing almost no other substances other than Al ₂ O ₃ and TiC is 7.3 × 10 ⁻⁶ / ° C., and thermal expansion is achieved by adding MgO. The coefficient has been lowered. Further, the content ratio of Al ₂ O ₃ and TiC hardly affects the thermal expansion coefficient itself.

Here, in particular, the content of MgO is preferably 40 to 50% by weight based on the total weight of Al ₂ O ₃ , TiC, and MgO. According to this, the thermal expansion coefficient of the spacer 10 can be set to about 8.5 to 9.0 × 10 ⁻⁶ / ° C., which is convenient. This case is particularly suitable for the magnetic disk 24 containing soda lime glass and the magnetic disk 24 containing N10 glass. Further, it is more preferable that the content of MgO is 43 to 47% by weight with respect to the total weight of Al ₂ O ₃ , TiC, and MgO.

The amount of TiC is, Al ₂ O _3, TiC, and, relative to the total weight of MgO, is preferably 20 to 30 wt%. Thereby, the spacer 10 having sufficient strength and sufficiently sintered can be obtained. The TiC content is more preferably 23 to 27% by weight. Here, if the amount of TiC is less than 20% by weight, the rigidity tends to decrease and the strength of the spacer tends to decrease. On the other hand, if the amount of TiC exceeds 30% by weight, it becomes difficult to sinter, becomes brittle, and the strength tends to decrease again.

Furthermore, since such a spacer 10 is a composite ceramics sintered body containing TiC and Al ₂ O _3, it exhibits the properties of Altic (AlTiC), which is a highly hard conductive ceramic, and has high strength. Yes. For this reason, when used as a spacer of a magnetic disk, the magnetic disk can be maintained at a predetermined interval. In addition, since such a spacer 10 has a specific resistance of about 1 to 1 × 10 ⁴ Ω · m and is conductive, static electricity or the like is hardly collected.

  Next, a method for manufacturing such a spacer will be described.

Such a spacer 10 is obtained by mixing Al ₂ O ₃ powder, TiC powder, and MgO powder, forming into a ring shape, firing the molded body at a predetermined temperature, and allowing to cool.

Below, the manufacturing method of the spacer which concerns on this embodiment is demonstrated in detail. First, Al ₂ O ₃ powder, TiC powder, and MgO powder as raw materials are prepared. Here, the raw material Al ₂ O ₃ powder is preferably a fine powder, and the average particle size is preferably 0.1 to 1 μm, particularly preferably 0.4 to 0.6 μm. The TiC powder is preferably fine powder, and the average particle size is preferably 0.1 to 3 μm, particularly preferably 0.5 to 1.5 μm. The MgO powder is preferably a fine powder, and the average particle size is preferably 0.1 to 3 μm, particularly preferably 0.5 to 1 μm.

And these powders are mixed and mixed powder is obtained. Here, these powders are mixed so that the MgO powder is contained in an amount of 35 to 55% by weight with respect to the total weight of the Al ₂ O ₃ powder, the TiC powder, and the MgO powder.

  Preferably, these powders are mixed so that 20 to 30% by weight of TiC is contained. Preferably, these powders are mixed so that MgO is contained in an amount of 40 to 50% by weight.

  Here, it is preferable to mix the powder in a ball mill or an attritor. In order to mix suitably, it is preferable to use, for example, ethanol, IPA, 95% denatured ethanol or the like as a solvent other than water. Moreover, it is preferable to mix these powders for about 10 to 100 hours. In addition, as a mixing medium in a ball mill or an attritor, it is preferable to use an alumina ball or a zirconia ball having a diameter of about 1 to 20 mm, for example.

  Next, the mixed powder thus mixed is spray granulated. Here, for example, it may be spray-dried in a warm air of about 60 to 200 ° C. of an inert gas such as nitrogen or argon containing almost no oxygen, whereby a granulated product of the mixed powder having the above composition is obtained. can get. Here, for example, the particle size of the granulated product is preferably about 50 μm to 200 μm.

  Next, if necessary, a solvent or the like is added to adjust the liquid content of the granulated product so that the solvent is contained in the granulated product by about 0.1 to 10% by weight.

Next, this granulated material is filled in a predetermined mold, and primary molding is performed by cold pressing to obtain a ring-shaped molded body. Here, for example, a granule is filled in a metal or carbon mold for forming a disk having an inner diameter of 150 mm, and cold pressing is performed at a pressure of about 5 to 15 MPa (50 to 150 kgf / cm ² ). That's fine.

  Subsequently, the primary molded body is hot pressed to obtain a sintered body. Here, for example, it is preferable that the firing temperature is 1200 to 1700 ° C., the pressure is 10 to 50 MPa (100 to 500 MPa), and the atmosphere is vacuum, nitrogen, or argon. The non-oxidizing atmosphere is used to prevent oxidation of TiC. Moreover, it is preferable to use a carbon mold. The sintering time is preferably about 1 to 3 hours.

  Then, after the appearance and the like are inspected, the upper and lower surfaces, the inner peripheral surface, and the outer peripheral surface are mechanically finished with a diamond grindstone or the like to complete the magnetic disk spacer 10.

  Further, the hard disk device as shown in FIG. 1 can be manufactured by interposing the spacer 10 between the magnetic disks 24 and assembling the spindle 70 by a known method.

  Next, examples of the spacer according to the present embodiment will be described.

(Example 1)
First, Al ₂ O ₃ powder (average particle size 0.5 μm, purity 99.9%), TiC powder (average particle size 0.5 μm, purity 99%, carbon content 19% or more, 1% or less of which is free graphite And a predetermined amount of MgO powder (average particle size 0.1 μm), weighed and mixed with ethanol in a ball mill for 30 minutes, and spray granulated in nitrogen at 150 ° C. to obtain a granulated product. Here, with respect to the total weight of the Al ₂ O ₃ powder, the TiC powder, and the MgO powder, the content of the MgO powder is 35% by weight, the content of the TiC powder is 25% by weight, and the Al ₂ O ₃ powder The composition of the granulated product was prepared so that the content of was 40% by weight.

Subsequently, these granulated materials are each formed into a ring shape at a pressure of about 0.5 MPa (50 kgf / cm ² ), and are hot-pressed in a vacuum atmosphere for 1 hour at a sintering temperature of 1600 ° C. and a press pressure of about 30 MPa (about The spacer for Example 1 was obtained by firing at 300 kgf / cm ² ).

(Examples 2 to 5)
A spacer of Example 2 was obtained in the same manner as Example 1 except that the MgO content was 40% by weight and the Al ₂ O ₃ content was 35% by weight. Further, a spacer of Example 3 was obtained in the same manner as Example 1 except that the content of MgO was 45% by weight and the content of Al ₂ O ₃ was 30% by weight. Further, a spacer of Example 4 was obtained in the same manner as Example 1 except that the content of MgO was 50% by weight and the content of Al ₂ O ₃ was 25% by weight. Further, a spacer of Example 5 was obtained in the same manner as in Example 1 except that the content of MgO was 55 wt% and the content of Al ₂ O ₃ was 20 wt%.

(Comparative Example 1 and Comparative Example 2)
A spacer of Comparative Example 1 was obtained in the same manner as in Example 1 except that the content of MgO was 30% by weight and the content of Al ₂ O ₃ was 45% by weight. Further, a spacer of Comparative Example 2 was obtained in the same manner as in Example 1 except that the content of MgO was 60% by weight and the content of Al ₂ O ₃ was 15% by weight.

(Example 6 to Example 9)
A spacer of Example 6 was obtained in the same manner as in Example 3 except that the content of TiC powder was 15 wt% and the content of Al ₂ O ₃ was 40 wt%. Further, a spacer of Example 7 was obtained in the same manner as Example 3 except that the content of TiC powder was 20% by weight and the content of Al ₂ O ₃ was 35% by weight. Further, a spacer of Example 8 was obtained in the same manner as Example 3 except that the content of TiC powder was 30% by weight and the content of Al ₂ O ₃ was 25% by weight. Further, a spacer of Example 9 was obtained in the same manner as in Example 3 except that the content of TiC powder was 35% by weight and the content of Al ₂ O ₃ was 20% by weight.

  The table | surface of FIG. 3 shows about the composition of each component in these Examples 1-9 and Comparative Examples 1-2. In addition, the thermal expansion coefficient, the three-point bending strength, and the sinterability are shown in the table of FIG. 3 for each spacer thus obtained. Furthermore, the relationship between the added amount of MgO and the coefficient of thermal expansion is shown in FIG. The three-point bending strength was measured with an autograph material testing machine manufactured by Shimadzu Corporation at a span distance of 30 mm and a crosshead speed of 0.1 mm / min.

As is clear from FIG. 4, when the MgO content is 35 to 55% by weight as in Examples 1 to 9, the thermal expansion coefficient is about 8.0 to 9.5 × 10 ⁻⁶ / ° C. . Moreover, as can be seen from Examples ₃ and 6 to 9, the weight ratio of Al ₂ O ₃ and TiC hardly affects the thermal expansion coefficient. Moreover, in order to obtain a spacer having a strength of 400 MPa or more, which is usually preferred, it was confirmed that the content of TiC is preferably 20% or more and 30% or less. In addition, when the weight ratio of TiC increases too much, it is thought that sinterability falls and intensity | strength falls.

  Furthermore, the strength of the spacer described above is sufficiently higher than the three-point bending strength of 324 MPa of alumina, which is preferable as a spacer.

1 is a schematic configuration diagram showing a hard disk device according to the present embodiment. It is a perspective view which shows the spacer of FIG. It is a table | surface which shows the composition of Examples 1-9 and Comparative Examples 1-2, a thermal expansion coefficient, and 3 point | piece bending strength. It is a graph which shows the relationship between a thermal expansion coefficient and the addition amount of MgO.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Spacer (magnetic disk spacer) 23 ... Glass substrate 24 ... Magnetic disk 25 ... Magnetic recording layer 20 ... Motor 18 ... Magnetic head 100 ... Hard disk device

Claims (6)

Having a sintered body containing Al ₂ O ₃ , TiC and MgO, the sintered body containing 35 to 55 wt% of MgO based on the total weight of Al ₂ O ₃ , TiC and MgO; Magnetic disk spacer. The magnetic disk spacer according to claim 1, wherein the sintered body contains 20 to 30% by weight of TiC based on the total weight of Al ₂ O ₃ , TiC, and MgO. The magnetic disk spacer according to claim 1, wherein the sintered body contains 40 to 50% by weight of MgO with respect to the total weight of Al ₂ O ₃ , TiC, and MgO. The magnetic disk spacer according to claim 1, wherein an outer shape of the sintered body is a ring. A plurality of magnetic disks each having a magnetic recording layer formed on a glass substrate;
A magnetic disk spacer interposed between the magnetic disks;
A motor for rotating the magnetic disk;
A magnetic head that performs at least one of writing information to the magnetic recording layer of the magnetic disk and reading information from the magnetic recording layer of the magnetic disk;
With
The magnetic disk spacer has a sintered body containing Al ₂ O ₃ , TiC, and MgO, and the sintered body contains MgO with respect to the total weight of Al ₂ O ₃ , TiC, and MgO. Hard disk device containing 35 to 55% by weight. The hard disk drive according to claim 5, wherein the sintered body of the magnetic disk spacer includes 20 to 30 wt% of TiC with respect to the total weight of Al ₂ O ₃ , TiC, and MgO.

Images