JP2006318583A - Glass substrate for information recording medium, information recording medium, and information recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the glass substrate from being broken caused by colliding with a ramp when the information recording device is dropped down. <P>SOLUTION: An information recording glass substrate has at least a main surface and an outer side surface. The main surface inclines so that the substrate becomes gradually thinner from the center to the outer side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an information recording medium glass substrate, an information recording medium, and an information recording apparatus.

  2. Description of the Related Art A substrate using a glass substrate is known as a substrate of a small hard disk device used for a notebook type personal computer or a card type storage medium. In such a portable hard disk device, for the purpose of protecting the magnetic head and the recording layer of the disk from external impact, the magnetic head is retracted to the ramp outside the disk while the device is stopped, There is known a ramp load type in which recording is performed by sliding a magnetic head out of a ramp when the apparatus is activated.

  In such a ramp load type hard disk device, a magnetic disk that does not cause any particular problems even if it is dropped or shocked when incorporated in a device other than the ramp load type is used. Regardless, it has been found that the glass substrate is damaged by a sudden impact such as dropping or collision. In particular, this problem was significant when a glass substrate that was not subjected to a tempering treatment was used.

  A typical example of a magnetic recording medium of a conventional hard disk device is shown in FIG. The glass substrate 100 on which the magnetic recording layer 200 is formed has a configuration as shown in FIG. That is, a flat chamfered portion 20 is formed between the main surface 10 and the side surface 40 at the outer end portion. According to the study of the present inventor, the storage medium is slightly bent because the lamp is located away from the disk but is always positioned so as to overlap the recording medium when viewed from the direction perpendicular to the main surface of the disk. It sometimes turned out that the substrate collided with the lamp, and a specific stress was concentrated on the boundary portion 30 between the main surface 10 and the chamfered portion 20 at the outer end portion of the glass substrate 100 to break the substrate.

In order to alleviate stress concentration at the boundary between the main surface and the chamfered portion, it is conceivable to form a curved surface between the main surface and the chamfered portion. Patent Documents 1 and 2 are known as techniques for providing a curved surface between a main surface and a chamfered portion.
JP-A-10-154321 JP 2002-100031 A

  However, the inventions described in Patent Documents 1 and 2 are intended to prevent the generation of particles due to rubbing between the corners of the glass substrate and the storage container, and to prevent the substrate from cracking due to a lamp collision. Patent Documents 1 and 2 do not describe how long the curved surface portion is provided. In addition, it is assumed that there is a flat chamfered portion having an angle of approximately 45 degrees with respect to the main surface and the outer surface, and it is difficult to prevent the substrate from being cracked due to a lamp collision. Thus, the actual situation is that a glass substrate for an information recording medium in consideration of preventing cracking of the substrate due to a lamp collision has not been proposed yet.

  Accordingly, an object of the present invention is to provide a glass substrate for an information recording medium, an information recording medium, and an information recording apparatus that can prevent the substrate from being cracked due to a lamp collision.

  As a result of investigations, the present inventors have found that this problem can be solved by controlling the outer end portion to a predetermined shape, and have reached the present invention.

  That is, the glass substrate for information storage media according to the present invention is a glass substrate for information storage media comprising at least a main surface and an outer surface, so that the thickness of the substrate decreases from the center toward the outer surface. The main surface is inclined.

  The inclination angle of the main surface may be 15 degrees or less.

  The inclination angle of the main surface may be constant or may increase continuously toward the outer surface.

  The glass substrate may have a strength that can be used as a recording medium substrate without performing a strengthening treatment.

  The glass substrate is used while being rotated around a fixed center.

  The glass substrate has a hole in the center, and the main plane between the inner diameter and the outer diameter is inclined.

  The information recording medium according to the present invention is characterized in that a recording layer is provided on the main surface of a glass substrate having any one of the above-described configurations.

  An information recording apparatus according to the present invention is arranged such that the information recording medium described above, a drive mechanism of the information recording medium, a head for reading and writing the information recording medium, and a tip overlaps with an end of the information recording medium. And a head driving mechanism for loading the head retracted on the lamp onto the information recording medium and unloading the head onto the lamp.

  According to the present invention, it is possible to provide a glass substrate that can effectively prevent cracking due to lamp collision when the information recording apparatus is dropped.

  FIG. 1 is an end sectional view showing an embodiment of a glass substrate for information recording medium according to the present invention. The overall configuration of the glass substrate 106 is a disk shape, and has a hole in the center. The central hole is used to fix the glass substrate 106 to the rotating member and rotate the glass substrate 106 around the center. The front main surface 10a and the back main surface 10b of the glass substrate 106 are smooth surfaces.

  As shown in FIG. 1, in the glass substrate 106, the main surface 10 a is slightly inclined so that the thickness of the substrate 106 becomes thinner as a whole from the central portion toward the outer surface 40. As described above, the main surface 10a is inclined from the central portion toward the outer side surface 40 in a tapered manner, so that the connection from the main surface 10a to the outer side surface 40 can be made smoother. If the connection is made more gently from the main surface 10a, stress concentration is less likely to occur. The inclination angle θ formed by the reference plane 91 and the inclined surface 92 of the main surface 10a is preferably 15 degrees or less. Furthermore, it is more preferable that the inclination angle θ of the main surface 10a is constant or continuously increases toward the outer surface, that is, draws a loose arc.

  By designing the shape of the outer end portion in this way, even when the information recording apparatus is dropped, even if the glass substrate bends and the outer end portion contacts the lamp 300, the thin inclined portion slides to make the lamp 300 slide. It is presumed that the impact caused by the contact is reduced in space and time. Therefore, stress does not concentrate near the boundary between the front main surface 10a and the thin inclined portion, and cracking does not occur.

  Since the main surface 10b on the back side and the side surface 40 are configured in the same manner as the front side, the tensile stress at the time of lamp collision is also dispersed, so that the glass substrate 106 can be more effectively prevented from cracking.

In the above embodiment, the influence of the stress concentration on the boundary between the side surface 40 and the thin inclined portion at the time of the lamp collision is not large, but the corner portion of the boundary is removed to prevent generation of dust due to rubbing with the storage container. It is preferably a curved surface.
<Substrate manufacturing method>
A disk-shaped glass body is obtained by directly pressing after melting the glass raw material or by cutting it out from a sheet glass formed by a downdraw method or the like using a grinding wheel. And it grinds so that it may become desired thickness using a diamond grindstone. And it grinds so that it may become a desired surface roughness for each side using the grindstone with a finer grain size than the said grindstone. Thereafter, the central portion is drilled using a cylindrical grindstone, and the inner and outer circumferences are ground and chamfered. Then, end surface polishing is performed by brush polishing or mechanical polishing using a polishing liquid so that the surface roughness of the inner and outer peripheral end surfaces of the glass substrate is within a predetermined range while rotating the glass substrate. Then, lapping is performed by blowing abrasive grains with a lapping apparatus to further reduce the surface roughness. Finally, polishing is performed using a polisher (note that cleaning is appropriately performed between the steps). In this way, a glass substrate for information recording media is obtained. The glass substrate having the configuration as shown in the above embodiment can be obtained by adjusting the process conditions from the end face polishing to the polishing.

More specifically, first, the end face shape of each glass plate is finished with a drum-shaped grindstone. Thereafter, the surface is polished by bringing a rotating nylon brush roller into contact with the end face while supplying the polishing liquid. At this time, by processing a plurality of substrates at the same time with a spacer in between, R can be formed above and below the substrates, and the processing time can be shortened. Thereafter, the main surface is polished. In the case of performing chemical strengthening, polishing conditions are set in advance so as to allow for deformation due to chemical strengthening so that the above-described shape is obtained after chemical strengthening.
<Material of glass substrate>
There is no restriction | limiting in particular and conventionally well-known various glass and glass ceramics can be used. Examples thereof include glass ceramics such as aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, or crystallized glass. Moreover, the glass by which the chemical strengthening process was given by the dealkalizing process, the chemical strengthening process by ion exchange, etc. may be sufficient. Although it is possible to improve impact resistance and vibration resistance if the glass is chemically strengthened, the present invention effectively prevents cracking due to collision with the lamp even if the glass is not chemically strengthened. be able to.

The aluminosilicate _glass, SiO 2: _62~75 wt%, Al ₂ O _3: 5~15 wt%, Li ₂ O: 4~10 wt%, Na ₂ O: 4~12 wt%, ZrO _2: 5 0.5 to 15 wt% as a main component, and the weight ratio of Na ₂ O / ZrO ₂ is 0.5 to 2.0, and the weight ratio of Al ₂ O ₃ / ZrO ₂ is 0.4 to 2.5. The glass for chemical strengthening etc. which are are preferable. Further, in order to eliminate protrusions on the surface of the glass substrate caused by the undissolved material of ZrO ₂ , SiO ₂ is 57 to 74%, ZnO ₂ is 0 to 2.8%, Al ₂ O _{3 in} terms of mol%. 3-15% of LiO ₂ 7 to 16% it is preferred to use chemical strengthening glass containing Na ₂ O 4~14%. Aluminosilicate glass and the like having such a composition have an increased bending strength, a deep compressive stress layer, and an excellent surface hardness when chemically strengthened.

In the present invention, for the purpose of improving impact resistance, vibration resistance and the like, the surface of the glass substrate can be subjected to chemical strengthening treatment by a low temperature ion exchange method. Here, the chemical strengthening method is not particularly limited as long as it is a conventionally known chemical strengthening method. For example, low-temperature chemical strengthening in which ion exchange is performed in a region not exceeding the transition temperature is preferable from the viewpoint of the glass transition point. . Examples of the alkali molten salt used for chemical strengthening include potassium nitrate, sodium nitrate, and nitrates obtained by mixing them.
<Substrate size and thickness>
There is no particular limitation on the substrate size, and various sizes such as 0.85 inch, 1 inch, 2.5 inch, 3 inch, and 3.5 inch can be used. There is no particular limitation on the thickness of the substrate, and it may be appropriately selected according to the substrate size.
<Magnetic disk manufacturing method>
A magnetic disk as an information recording medium is manufactured by sequentially forming an underlayer, a magnetic layer, a protective layer, and a lubricating layer on the glass substrate obtained as described above. A magnetic recording medium usually has a predetermined flatness and surface roughness, and an underlayer, a magnetic layer, a protective layer, and a lubricating layer are provided on a glass substrate for a magnetic disk that has been subjected to chemical strengthening treatment on the surface as necessary. Produced by sequentially laminating.

  The underlayer is selected according to the magnetic layer. Examples of the underlayer include an underlayer made of at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, and Al. In the case of a magnetic layer containing Co as a main component, Cr alone or a Cr alloy is preferable from the viewpoint of improving magnetic characteristics. Further, the base layer is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. Examples thereof include multilayer underlayers such as Cr / Cr, Cr / CrMo, Cr / CrV, CrV / CrV, Al / Cr / CrMo, Al / Cr / Cr, Al / Cr / CrV, and Al / CrV / CrV. .

  The material of the magnetic layer in the magnetic recording medium is not particularly limited. Examples of the magnetic layer include magnetic thin films such as CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, CoNiPt containing Co as a main component, CoNiCrPt, CoNiCrTa, CoCrTaPt, and CoCrPtSiO. The magnetic layer may be a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrTaPt / CrMo / CoCrTaPt, etc.) in which the magnetic film is divided by a non-magnetic film (for example, Cr, CrMo, CrV) to reduce noise. Good.

As a magnetic layer corresponding to a magnetoresistive head (MR head) or a large magnetoresistive head (GMR head), an impurity element selected from Co, alloys, Y, Si, rare earth elements, Hf, Ge, Sn, Zn Or those containing oxides of these impurity elements. As the magnetic layer, in addition to the above, ferritic, iron - rare-earth and, Fe in a non-magnetic film made of SiO _2, BN, Co, FeCo, the structure in which the magnetic particles are dispersed, such CoNiPt granular It may be. Further, the magnetic layer may be of an internal type or a vertical type.

  The protective layer in the magnetic recording medium is not particularly limited. Examples of the protective layer include a Cr film, a Cr alloy film, a carbon film, a zirconia film, and a silica film. These protective films can be continuously formed by an in-line sputtering apparatus together with an underlayer, a magnetic layer, and the like. Further, these protective films may be a single layer, or may be a multilayer structure composed of the same or different films.

Another protective layer may be formed on the protective layer or instead of the protective layer. For example, in place of the protective layer, colloidal silica fine particles are dispersed and applied in a tetraalkoxylane diluted with an alcohol-based solvent on a Cr film, and further baked to form a silicon oxide (SiO ₂ ) film. It may be formed.

The lubricating layer in the magnetic recording medium is not particularly limited. For example, the lubricating layer may be obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon, and applying it to the surface of the medium by dipping, spin coating, or spraying. Go and form.
<Aspects other than glass substrates for hard disks>
It can also be used as a glass substrate for magneto-optical disks and a disk substrate for electro-optics such as optical disks.
<Configuration of information recording device>
FIG. 2 is a perspective view showing a load / unload type hard disk drive in which a magnetic disk is mounted. The hard disk device 500 includes a magnetic disk 401, a recording / reproducing head 502, a suspension 504 that supports the recording / reproducing head 502, and a head actuator 509 that includes an arm 506 that fixes the suspension 504.

  The head actuator 509 is attached so that the arm 506 can rotate with respect to the housing 501 about the pivot 507. The head actuator 509 is rotationally driven by a voice coil motor 508 provided on the opposite side of the suspension 504 across the pivot 507. Furthermore, power is supplied to the head actuator 509 and signals are exchanged with the recording / reproducing head 502 via a flexible printed board 505 fixed to the arm 506.

  In the hard disk device 500, a lift tab 503 is provided at the tip of the suspension 504, and the lift tab 503 is guided to a position regulation lamp 300 attached to the housing 501 so as to overlap with the end of the disc 401, whereby the recording / reproducing head. Unloading is performed for retracting 502 from the surface of the magnetic disk 401 to the outside, and loading for landing the head 502 from the outside of the disk 401 to the surface.

  The lift tab 503 is a protrusion provided at the tip of the suspension 504 and is located on the tip side of the head 502. The position restricting ramp 300 has a slope with which the lift tab 503 comes into contact. While the lift tab 503 is in contact with the slope of the ramp 300, the distance between the two suspensions 504 is restricted, and the heads 502 contact with each other and the head 502. And the disc 401 are prevented from contacting each other.

The head 502 floats above the surface of the disk 401 by an air flow generated by the rotation of the disk 401 mounted on the rotary spindle. For this reason, when the head 502 is loaded onto the surface of the disk 401, the lift tab 503 is supported by the position restriction lamp 300 until the head 502 reaches the surface of the disk 401. When unloading the head 502 to the outside of the disk 401, the lift tab 503 is supported by the position restriction lamp 300 before the head 502 comes out of the disk 401.
<Example>
A predetermined amount of raw material powder was weighed into a platinum crucible, mixed, and then melted at 1550 ° C. in an electric furnace. After the raw materials were sufficiently dissolved, a stirring blade was inserted into the glass melt and stirred for about 1 hour. Thereafter, the stirring blade was taken out and allowed to stand for 30 minutes, and then the melt was poured into a jig to obtain a glass block. Thereafter, the glass block was reheated to near the glass transition point of each glass, and slowly cooled to remove strain. The obtained glass block was sliced into a disc shape of about 1.5 mm in thickness and 2.5 inches, and the inner periphery and outer periphery were cut out using a cutter with concentric circles. Then, both surfaces were roughly polished, polished and washed to produce a glass substrate. By changing the polishing conditions, glass substrates (sample numbers 1 to 3) having the outer end shape described above were obtained.

  Specifically, when performing the end surface polishing, the surface roughness of the inner and outer peripheral end surfaces of the glass substrate is within a predetermined range while rotating the glass substrate by brush polishing or mechanical polishing using slurry. Polished. For sample number 1, the grindstone was tilted at a predetermined angle with respect to the reference surface, thereby forming an inclined surface with the main surface tilted as a whole. Sample No. 2 was subjected to polishing conditions such that a curved surface was formed only between the main surface and the flat chamfered portion and between the flat chamfered portion and the side surface with respect to the glass substrate. For sample number 3, the polishing conditions were such that neither a chamfered portion nor a curved surface was provided between the main surface and the side surface.

As the glass composition, in mol%, the SiO ₂ 66.8%, the _{Al 2 O 3 11.3%, B} 2 O 3 3.4%, the Li ₂ O 2.5%, Na ₂ O 7.0%, K ₂ O 2.5%, CaO 3.0%, TiO ₂ 1.9%, ZrO ₂ 0.6%, La ₂ O ₃ 0.7%, Sb ₂ O ₃ was 0.3%.

  A magnetic layer was formed on the obtained glass substrate to obtain information recording media (sample numbers 1 to 3). Samples 2 and 3 are shown as comparative examples. The information recording medium was set on a ramp load type hard disk device, and then it was inspected for scraping caused by rubbing with the container. In addition, a drop test was performed to examine whether the glass substrate was cracked. The results are shown in Table 1.

  As shown in Table 1, in the information recording medium according to the present invention, it was confirmed that the glass substrate was not broken by a drop test, and that no abrasion occurred due to rubbing with the container.

It is edge part sectional drawing of the glass substrate which concerns on one Embodiment of this invention. It is an exploded sectional view of an information recording device. It is a perspective view of an information recording medium. It is edge part sectional drawing of the glass substrate which concerns on a prior art.

Explanation of symbols

10a: Front main surface 10b: Back main surface 40: Side surface 91: Reference surface 92: Inclined surface 106: Glass substrate 401: Magnetic disk 500: Hard disk device

Claims (8)

  An information storage medium glass substrate having at least a main surface and an outer surface, wherein the main surface is inclined so that the thickness of the substrate decreases from the central portion toward the outer surface. Glass substrate for media.   The glass substrate for an information storage medium according to claim 1, wherein the inclination angle of the main surface is 15 degrees or less.   The glass substrate for an information storage medium according to claim 1, wherein the inclination angle of the main surface is constant or continuously increases toward the outer surface.   The glass substrate for an information storage medium according to any one of claims 1 to 3, wherein the glass substrate has a strength that can be used as a substrate for a recording medium without performing a strengthening treatment.   The glass substrate for an information storage medium according to any one of claims 1 to 4, wherein the glass substrate is used by being rotated around a fixed center.   The glass substrate for an information storage medium according to any one of claims 1 to 5, wherein the glass substrate has a hole in a central portion, and a main plane between an inner diameter and an outer diameter is inclined.   An information recording medium comprising a recording layer provided on a main surface of the glass substrate for an information recording medium according to any one of claims 1 to 6. 8. An information recording medium according to claim 7, a drive mechanism for the information recording medium, a head for reading and writing the information recording medium, a lamp arranged so that the tip thereof overlaps the end of the information recording medium, and retreating to the lamp An information recording apparatus comprising: a head driving mechanism for loading a head to an information recording medium and unloading the head to a lamp.

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