JP2006059463A - Glass substrate for magnetic disk, its reinforcement method and hard disk drive using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass substrate for a magnetic disk by which a glass magnetic disk is not damaged even when an impact of falling or the like is loaded and which can be inexpensively obtained, to provide its reinforcement method and to provide a hard disk drive using the same. <P>SOLUTION: A heterogeneous phase is formed on the surface or the inner part of glass or compression stress is generated on the surface of the glass using a wind cooling method or an ion exchange method only at inner edge parts on the periphery of a center hole of the glass magnetic disks 10a and 10b coming in contact with a fixing part of the hard disk drive. By providing a reinforcement treatment part using either one method of these reinforcement treatment methods, stress concentration is produced and reinforcement treatment of the part which is easily damaged can be intensively performed and the glass magnetic disks 10a and 10b having excellent impact resistance can be obtained without performing reinforcement treatment of the entire surfaces thereof. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a glass substrate for a magnetic disk, a method for strengthening the same, and a hard disk drive using the same.

  In recent years, a large capacity has been demanded for hard disk drives, and glass magnetic disks in which a magnetic layer and a lubricating layer are provided on a glass disk substrate have been used. However, since glass is a brittle material, it can be damaged relatively easily when subjected to excessive impacts such as handling when manufacturing hard disk drives, falling as a product or being used as a computer component. End up. Therefore, measures to reinforce the glass substrate used for glass magnetic disks can be considered so as not to be damaged when such an impact is applied. A tempering treatment using a method of applying compressive stress to the glass surface is performed using a chemical tempering treatment method using exchange. The glass magnetic disk strengthening process by these methods is performed on the entire surface of the magnetic disk glass substrate. However, in order to improve the strength by controlling the surface roughness of the inner peripheral end surface of the doughnut-shaped glass substrate within a predetermined range, It has been proposed to perform chemical treatment on the peripheral end surface (see Patent Document 1). As another strengthening method of the glass material, a strengthening process is proposed in which the ultrashort pulse laser beam is focused on the glass material to form a heterogeneous phase on the surface of the glass material or inside the glass material (Patent Document). 2).

On the other hand, for fixing the glass magnetic disk to the hard disk drive, as shown in FIG. 5, a single glass magnetic disk 10a is laminated on the flange portion 12 of the hub 11 of the spindle motor, and an annular spacer 14 is formed thereon. The other disk 10b is stacked through the disk, and a disk presser 13 having a presser portion formed in a circumferential shape is applied to the disk 10b and fixed to the other end of the spindle motor hub with a screw 15 or the like. . Members in contact with the glass magnetic disks 10a and 10b such as the hub 11 of the spindle motor, the spacer 14, and the disk retainer 13 are made of a metal having high rigidity and hardness such as stainless steel. Therefore, when an impact is applied from the outside to the hard disk drive loaded with a glass magnetic disk, stress concentrates on the periphery of the spindle motor hub, spacer, and disk retainer that fixes the glass magnetic disk to the hard disk drive. However, most of the damage occurs in this portion, that is, the inner edge around the central hole of the glass magnetic disk having a donut shape.
Japanese Patent Application Laid-Open No. 07-230621 JP 2003-28604 A

As described above, since the conventional glass magnetic disk strengthening process is performed on the entire surface of the magnetic disk glass substrate, the manufacturing cost is increased, and the chemical strengthening process is not necessarily advantageous for forming the magnetic layer. In addition, since the chemical strengthening process is performed only on the center hole surface, the part described in Patent Document 1 is not strengthened at the place where stress is concentrated when fixed to the hard disk drive, and an impact is applied. It is difficult to prevent damage.
Therefore, the present invention relates to a glass substrate for a magnetic disk that can be obtained at a low cost without damaging the glass magnetic disk even when an impact such as a drop is applied, a strengthening method thereof, and a hard disk using the same. The purpose is to provide a drive.

  As a result of repeating various studies and experiments in order to solve the above problems, the present inventor does not necessarily need to subject the entire glass substrate for magnetic disk to a tempering treatment in order to improve the impact strength of the glass magnetic disk. By strengthening only the part where the glass magnetic disk is in contact with the fixed part of the hard disk drive, the overall impact resistance is improved, it can be strengthened at low cost, and it is advantageous for magnetic layer formation. It has been obtained and the present invention has been achieved.

  That is, the glass substrate for a magnetic disk of the present invention that achieves the above object is a glass substrate for a magnetic disk having a donut shape used for a hard disk drive, and an inner edge around the central hole of the glass substrate for a magnetic disk, A reinforcing treatment portion having a predetermined width is provided from the inner peripheral end of the center hole. It is desirable that the strengthened portion has a width that is at least as large as a range in which a fixing member that fixes the glass substrate for a magnetic disk contacts the hard disk drive.

Further, the method for strengthening a glass substrate for a magnetic disk of the present invention is a method for strengthening a glass substrate for a magnetic disk having a donut shape used for a hard disk drive, and an inner edge portion around a central hole of the glass substrate for a magnetic disk, The impact strength of the glass disk substrate is increased by strengthening the range of a predetermined width from the inner peripheral end of the center hole. As the strengthening treatment method, an ultrashort pulse laser beam is condensed and irradiated to form a heterogeneous phase on the surface of the magnetic disk glass substrate and / or the inside of the magnetic disk glass substrate, thereby providing a strengthening treatment portion, ion exchange A compressive stress is generated on the surface of the glass substrate for a magnetic disk using a method to provide a strengthened portion, and a compressive stress is generated on the surface of the glass substrate for a magnetic disk using an air cooling method. This can be achieved by adopting any means for providing the reinforcing treatment portion.
The hard disk drive of the present invention is a hard disk drive characterized by using any one of the above magnetic disk glass substrates.

  The glass substrate for a magnetic disk of the present invention is provided with a strengthening portion locally only on the inner edge around the center hole, not on the entire surface of the magnetic disk glass substrate. An inexpensive glass substrate for a magnetic disk can be provided. Then, the present invention provides a stress concentration using any one of the strengthening treatment methods, in which a heterogeneous phase is formed on the glass surface or inside the glass, or a compressive stress is generated on the glass surface using an air cooling method or an ion exchange method. It is possible to reliably provide a strengthened portion only at the inner edge around the center hole, which is easily damaged, and is extremely unlikely to be damaged when an impact such as dropping is applied.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing a main part of a hard disk drive apparatus using a magnetic disk glass substrate according to an embodiment of the present invention. In the drawing, members similar to those of the conventional hard disk drive device shown in FIG. 5 are given the same reference numerals, and detailed description thereof is omitted.
As shown in FIG. 2, the glass magnetic disk 10 comprising the glass substrate for magnetic disk of the present embodiment fixed to the hard disk drive shown in FIG. 1 is one of the doughnut-shaped magnetic disk glass substrates (glass magnetic disk 10). A reinforcing treatment portion 10e indicated by hatching is provided from the peripheral end portion 16 to the inner edge portion of the width W. As shown in FIG. 1, the strengthened portion 10 e provided at the inner edge with a width W from the inner peripheral end 16 is used to fix the glass magnetic disk in a hard disk drive such as the hub 11 of the spindle motor, the spacer 14, and the disk retainer 13. It is provided up to a position corresponding to each end position so as to cover all the surfaces in contact with the members. Preferably, as shown in FIGS. 1 and 3, the glass magnetic disk is provided so that it protrudes to the outer peripheral side from the respective end portions of the fixing member, and more preferably protrudes by 1 mm or more. If the tempered portion 10e is provided so as to be within the respective ends of the fixing member of the glass magnetic disk, when the impact force is applied, the impact force is concentrated on the non-strengthened portion and the glass magnetic disk is damaged. End up.

As a glass material used for a glass substrate for a magnetic disk to be a glass magnetic disk of the present invention, an ordinary oxide glass can be used, but it is preferable to use a glass having a composition with few cracks. As a glass having such a composition, 5~15mass% of _Na 2 O, _0~10mass% of _Li 2 O, 5~15mass% of _Al 2 _O 3, _0~6mass% of CaO, 2~10mass% of TiO _{2, 53~75mass%} of _SiO 2, Nb oxide and / or V oxides calculated as _Nb 2 _{O 5} or _V 2 _{O 5} glass material containing 0.1～10Mass% in terms of 5~15mass% Na ₂ O, 0~10mass% of _Li 2 O, _5~15mass% of _Al 2 _O 3, _0~6mass% of CaO, 2~6mass% of _TiO 2, _0~5mass% of _ZrO 2, _53~75mass% of SiO _2, Nb oxide and / or glass material containing 0.1～10Mass% of V oxide calculated as _Nb 2 _{O 5} or terms _{of V} 2 _{O 5} or 5～15Mass% of _Na 2 O,, the 0～10Mass% li ₂ O, the 5~15mass% Al _{2 3, 0.5~6mass%} of CaO, _TiO 2 of 2~10mass%, _ZrO 2 of 0~5mass%, containing SiO ₂ of 53~75mass%, and 1% to 15% of _B 2 _{O 3} and 0 glass material containing ～5Mass% of _{K 2} O, or 5～15Mass% of _Na 2 O, _0~10mass% of _Li 2 O, 5~15mass% of _Al 2 _O 3, _0.5~6mass% of CaO , _TiO 2 of 2~10mass%, _ZrO 2 of 0~5mass%, containing SiO ₂ of 53~75mass%, and the 0～15Mass% of _B 2 _{O 3} and 0.5～5Mass% of _{K 2} O The glass material contained is desirable.

As a method for providing a strengthening treatment portion having a predetermined width W from the inner peripheral end portion of the center hole of the glass substrate for magnetic disk, the following strengthening treatment method that has been performed for strengthening the glass material can be used. For example, a pulse width of an order of 1 × 10 ⁻¹⁵ seconds having energy of several nj to 1 mj, ultrashort wavelength pulse laser light of 400 to 1000 nm is converged into a spot shape of 100 μm or less using a lens or the like, and the convergence point is determined. The donut-shaped glass substrate for a magnetic disk is scanned and moved inside and / or on the surface of the inner edge around the center hole, and a phase different from the surrounding is formed inside and / or on the surface of the inner edge around the center hole. Or, apply potassium nitrate to the inner edge of both sides around the center hole of the glass substrate for magnetic disks, and heat to 300-500 ° C to exchange Na ions and K ions of potassium nitrate to give compressive stress to the surface. To do. Alternatively, the glass substrate for magnetic disk can be heated in a heating furnace, and a strengthened portion can be provided on the inner edge of the glass substrate for magnetic disk by using any one of these strengthening methods. As described above, it is desirable that the strengthening treatment is performed up to both surfaces and / or the inside of the inner edge portion around the center hole of the glass substrate for magnetic disks.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
As a glass substrate for a magnetic disk, 5.0 mass% Na ₂ O, 3.6 mass% Li ₂ O, 12.7 mass% Al ₂ O ₃ , 0.5 mass% CaO, 3.7 mass% TiO ₂ , Outer diameter 65 mm, inner diameter 20 mm, thickness 0.635 mm made of 57.3 mass% SiO ₂ , 7.6 mass% B ₂ O ₃ , 1.8 mass% K ₂ O, 7.8 mass% Nb ₂ O ₅ The doughnut-shaped glass polishing substrate was placed on a stage movable in the horizontal direction and the height direction, and a pulse width of 1.2 × 10 ⁻¹³ seconds oscillated from a titanium sapphire laser on one surface of the glass polishing substrate. After fixing the position where the ultrashort wavelength pulse laser beam with a wavelength of 600 nm is converged into a 30 μm spot using a lens or the like and the output is adjusted to 50 mW, the stage is 21 m concentric with the central hole of the glass polishing substrate. The diameter, 22 mm diameter, 23 mm diameter, 24 mm diameter, 25 mm diameter, 26 mm diameter, 27 mm diameter, 28 mm diameter, 29 mm diameter, 30 mm diameter, 31 mm diameter, and 32 mm diameter of each of the 12 rows are moved circularly, A heterogeneous phase was formed on the inner edge surface of about 6 mm from the inner peripheral edge of the glass polishing substrate. Next, a heterogeneous phase was formed on the surface of the inner edge of about 6 mm from the inner peripheral edge in the same manner as above on the surface of the other side of the glass polishing substrate. In this manner, a glass magnetic disk comprising a glass substrate for magnetic disk whose inner edge was reinforced was prepared.

(Example 2)
As a magnetic disk glass substrate, a heterogeneous phase was formed in the same manner as in Example 1 on both the front and back surfaces of a doughnut-shaped glass polishing substrate having the same composition as in Example 1 and the same size and shape as in Example 1. Thereafter, the position where the pulse laser beam converges is fixed at a position of a depth of 0.2 mm from the surface of the glass polishing substrate surface, and a depth of 0.2 mm from both the front and back surfaces of the glass polishing substrate surface in the same manner as in Example 1. A heterogeneous phase was formed on the surface of the inner edge of about 6 mm from the inner peripheral end of the position. In this way, a heterogeneous phase was formed at a position of a depth of 0.2 mm from both the front and back surfaces of the inner edge portion of about 6 mm from the inner peripheral end portion and the inner edge portion of about 6 mm from the inner peripheral end portion. Thus, a glass magnetic disk comprising a glass substrate for a magnetic disk in which the surface of the inner edge portion and the inside thereof were reinforced was prepared.

(Example 3)
As a glass substrate for a magnetic disk, 5.0 mass% Na ₂ O, 5.0 mass% Li ₂ O, 13.0 mass% Al ₂ O ₃ , 0.5 mass% CaO, 3.0 mass% TiO ₂ , From the inner peripheral edge of a doughnut-shaped glass polishing substrate having the same dimensional shape as Example 1 consisting of 63.5 mass% SiO ₂ , 9.0 mass% B ₂ O ₃ , and 1.0 mass% K ₂ O The surface of the inner edge having a width of about 7 mm was coated with a paste in which kaolin was impregnated with potassium nitrate, and then heated at 400 ° C. for 15 hours to give a compressive stress to the surface. In this manner, a glass magnetic disk comprising a glass substrate for magnetic disk whose inner edge was reinforced was prepared.

Example 4
As a glass substrate for a magnetic disk, the following conditions are applied to an inner edge portion having a width of about 7 mm from an inner peripheral end portion of a doughnut-shaped glass polishing substrate having the same composition as in Example 2 and the same size and shape as in Example 1. The air cooling strengthening treatment was applied. That is, a magnetic disk glass substrate is heated to 600 ° C. in a heating furnace, and cold air jets are blown from a plurality of nozzles arranged circumferentially on both sides around the central hole of the magnetic disk glass substrate as follows. Then, compressive stress was applied to the surface. Thus, a glass magnetic disk composed of a glass substrate for magnetic disk, which was reinforced in the range of a predetermined width W from the inner peripheral end of the center hole, was prepared.
[Air cooling method]
28 holes of 1.5 mm diameter with 0.8 mm spacing on each circumference of 7 rows of concentric 21 mm diameter, 23 mm diameter, 25 mm diameter, 27 mm diameter, 29 mm diameter, 31 mm diameter, and 33 mm diameter 31 rows, 34 pieces, 36 pieces, 39 pieces, 42 pieces, 45 pieces, 7 rows of air-cooled nozzles drilled continuously in a ring shape, rotating in parallel on both sides of the glass substrate for magnetic disk Cooling air jets were sprayed from these holes to the inner edge of a width of about 7 mm from the inner periphery of the glass substrate for magnetic disk while cooling the nozzle while rotating the nozzle.

(Comparative example)
As a magnetic disk glass substrate, a glass magnetic disk comprising a glass polishing substrate having a donut-like shape having the same composition as in Example 1 and the same size and shape as in Example 1 was prepared.

  The configuration shown in FIG. 1 or FIG. 3 using two glass magnetic disks that are tempered on the inner edge of Examples 1 to 4 and two glass magnetic disks that are not tempered on the inner edge of the comparative example. Created a hard disk drive. That is, one glass magnetic disk is laminated on a spindle motor hub having a diameter of 24 mm at the outer end of the flange portion in contact with the glass magnetic disk, and the diameter of the outer peripheral end of the portion in contact with the glass magnetic disk thereon. Another glass magnetic disk was laminated through a spacer having a diameter of 24 mm, and a disk presser having a diameter of 23 mm in circumferential contact with the glass magnetic disk was fixed thereon to constitute a hard disk drive. Next, as shown in FIG. 4, the hard disk drive 1 was fixed on a stainless steel plate 6 of 30 cm × 30 cm × 15 mm so that the glass magnetic disk was parallel to the stainless steel plate 6. On the other hand, a stainless steel plate 8 having a thickness of 30 mm and a silicon rubber plate 9 having a thickness of 2 mm is placed on the concrete floor 7 and a stainless steel plate 6 to which the hard disk drive 1 is fixed is placed on the stainless steel plate 6 to an arbitrary height. The height at which at least one of the glass magnetic disks was damaged was measured by dropping from the height H. This test was performed five times with the glass magnetic disk changed, and the damage height was measured, and the average value was taken as the damage fall height. Table 1 shows the damage drop heights of these drop tests.

  As shown in Table 1, the hard disk drive constructed by incorporating the glass magnetic disk having the reinforced portion at the inner edge portion of the present invention is more than the hard disk drive constructed by incorporating the glass magnetic disk without the reinforced portion at the inner edge portion. Even if it was dropped from a high position and a larger impact strength was applied, it was difficult to cause damage. Therefore, it has been confirmed that the present invention has a very remarkable effect in improving the impact resistance of the glass magnetic disk.

  The glass substrate for a magnetic disk according to the present invention is provided with a strengthened portion by locally forming a heterogeneous phase only at the inner edge around the center hole, not on the entire surface of the glass substrate for the magnetic disk, or by generating a compressive stress Thus, a shock-resistant buffer layer that improves impact resistance is formed at a low cost, and a hard disk drive constructed by incorporating a glass magnetic disk made of the glass substrate for a magnetic disk is capable of dropping from a high place. Even if a large impact strength is applied, the glass magnetic disk will not be damaged. Handling when manufacturing a hard disk drive, even if it is subjected to impacts such as dropping when distributed as a product or used as a computer part, glass The possibility of damage to the magnetic disk is extremely low, making it suitable as a highly reliable hard disk drive It can be applied.

It is a principal part section schematic diagram showing an example of a hard disk drive using a glass magnetic disk which consists of a glass substrate for magnetic disks concerning an embodiment of the present invention. It is a schematic explanatory drawing which shows the reinforcement | strengthening part of the glass substrate for magnetic discs concerning embodiment of this invention. It is principal part cross-sectional schematic which shows an example of the hard disk drive using the glass magnetic disc which consists of the glass substrate for magnetic discs concerning other embodiment of this invention. It is explanatory drawing of a hard-disk drive drop strength measurement. It is a principal part cross-sectional schematic diagram of the hard disk drive using the conventional glass magnetic disk.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hard disk drive 6 Stainless steel plate 7 Concrete floor surface 8 Stainless steel plate 9 Silicon rubber plate 10 Glass magnetic disk 10a Glass magnetic disk 10b Glass magnetic disk 10e Strengthening part of glass substrate for magnetic disks 11 Spindle motor hub 12 Flange part 13 Disk presser 14 Spacer 15 Fixing means 16 Inner peripheral edge H Drop height W Width of strengthened portion

Claims (7)

  A glass substrate for a magnetic disk having a donut shape used in a hard disk drive, wherein a reinforcing treatment portion having a predetermined width from an inner peripheral end of the center hole is provided at an inner edge around the center hole of the glass substrate for the magnetic disk A glass substrate for a magnetic disk, characterized by comprising:   2. The glass substrate for a magnetic disk according to claim 1, wherein the strengthened portion has a width that is equal to or larger than a range in which a fixing member that fixes the glass substrate for a magnetic disk contacts at least a hard disk drive.   A method for strengthening a glass substrate for a magnetic disk having a donut shape used in a hard disk drive, wherein a range of a predetermined width from the inner peripheral edge of the center hole is strengthened on the inner edge around the center hole of the glass substrate for the magnetic disk A method for strengthening a glass substrate for a magnetic disk, wherein the impact strength of the glass substrate for a magnetic disk is increased by processing.   The strengthening treatment is characterized in that an ultrashort pulse laser beam is condensed and irradiated to form a heterogeneous phase on the surface of the magnetic disk glass substrate and / or the inside of the magnetic disk glass substrate, thereby providing a strengthening treatment portion. A method for strengthening a glass substrate for a magnetic disk according to claim 3.   The glass substrate for a magnetic disk according to claim 3, wherein the strengthening treatment provides a strengthening portion by generating a compressive stress on the surface of the glass substrate for the magnetic disk using an ion exchange method. How to strengthen.   4. The glass substrate for a magnetic disk according to claim 3, wherein the strengthening treatment provides a strengthening treatment portion by generating a compressive stress on the surface of the glass substrate for the magnetic disk using an air cooling method. How to strengthen.   A hard disk drive comprising the glass substrate for a magnetic disk according to claim 1.

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