JP2010238302A - Method of producing glass substrate for magnetic disk and electroplated grinding wheel used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a glass substrate for a magnetic disk which has high productivity and does not cause chipping, and to provide an electroplated grinding wheel having a long life. <P>SOLUTION: The method of producing a glass substrate for a magnetic disk includes a chamfering step of forming a chamfered surface between a pair of main surfaces and an end face of a glass substrate having the pair of main surfaces and the end face. In the chamfering step, an automatically dressed electroplated grinding wheel is used to perform chamfering. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a glass substrate for a magnetic disk used in a magnetic disk device such as a hard disk drive device (HDD device), and an electrodeposition grindstone used therefor.

  There is a magnetic disk as a magnetic recording medium mounted on a hard disk drive device (HDD device). A magnetic disk is manufactured by laminating a magnetic layer or a protective layer on a substrate, a glass substrate, or a ceramic substrate on which a NiP film is deposited on a metal plate made of an aluminum-magnesium alloy or the like. Conventionally, an aluminum alloy substrate has been widely used as a substrate for a magnetic disk. However, with recent downsizing, thinning, and high-density recording of magnetic disks, surface flatness and A glass substrate having excellent strength with a thin plate has been used.

  Such a magnetic disk substrate has a material processing step and a first lapping step; an end shape step (coring step for forming a hole, a chamfered surface at an end (outer peripheral end and / or inner peripheral end). Chamfering step to be formed (chamfered surface forming step)); end surface polishing step (outer peripheral end and inner peripheral end); second lapping step; main surface polishing step (first and second polishing step); chemical strengthening step; It is manufactured through processes such as inspection processes.

  The chamfering (chamfering process) is a process of giving a predetermined gradient to the peripheral part (edge part) of the inner and outer diameters of the annular glass substrate (Patent Document 1). In chamfering, an electrodeposition grindstone is used to grind the edge portions of the inner and outer diameters of the glass substrate into a predetermined shape. For this electrodeposition grindstone, diamond abrasive grains are used. The electrodeposition grindstone causes chipping on the glass substrate due to variations in the electrodeposition state of the diamond abrasive grains, the quality of the abrasive grain shape, and the accuracy of apparatus attachment. In order to avoid this chipping, dressing (shaping, clogging) is performed on the electrodeposited grinding stone to adjust the truing (shape formation) and final finish.

  FIGS. 3A to 3C are diagrams for explaining truing and dressing of an electrodepositing grindstone. As shown in FIG. 3A, when diamond abrasive grains are electrodeposited on the base material 31, the diamond abrasive grains 33 are deposited on the base material 31 via the plating layer 32. In this state, there are abrasive grains and protrusions 35 called floating stones 34. If chamfering is performed in the presence of the float stones 34 and the protrusions 35, the glass substrate is damaged (chipping occurs). In addition, when there is the float stone 34, the contact with the glass substrate becomes non-uniform due to non-uniformity of embedding of the abrasive grains. For this reason, truing is performed in order to correct the non-uniformity of removal of the float stone 34 and embedding of the abrasive grains.

  When truing is performed, as shown in FIG. 3B, the uniformity of embedding of the abrasive grains is maintained and chipping is reduced, but the truing material accumulates between the diamond abrasive grains 33 and the state of the abrasive surface (Clogging 36) occurs. Further, when truing is performed, the grinding surfaces are too aligned and the processing load increases. Chipping occurs due to the clogging 36 and the high processing load. For this reason, as shown in FIG.3 (c), dressing work is performed for the dressing work for making the unevenness | corrugation of an abrasive surface, and clogging improvement.

JP 2000-52212 A

  However, since both truing and dressing are performed manually, the level of skill by the operator determines the quality. In order to eliminate such variation by the worker, dummy processing is performed to omit truing work and dressing work. Here, the dummy processing means that the product is a non-defective product from the point of time when normal production is performed and no chipping failure occurs, and processing before that. Such dummy processing has the disadvantages that the productivity is reduced and the glass substrate used for the dummy processing is wasted. In addition, the electrodeposition grindstone that is manually performed for both truing and dressing as described above has a disadvantage that its life is short because the shape changes every time the number of machining passes.

  This invention is made | formed in view of this point, and it aims at providing the manufacturing method of the glass substrate for magnetic discs which has high productivity, and does not produce a chipping, and an electrodeposition grindstone with a long lifetime.

  The method of manufacturing a glass substrate for a magnetic disk according to the present invention includes a chamfering step of forming a chamfer surface between the pair of main surfaces and the end surfaces of a glass substrate having a pair of main surfaces and end surfaces. In the chamfering step, chamfering is performed using an automatically dressed electrodeposition grindstone.

  According to this method, since the automatically dressed electrodeposition grindstone is used, the abrasive grain shape quality of the electrodeposition grindstone can be stabilized. For this reason, it is possible to eliminate chipping in the chamfering process. Further, since the shape of the electrodeposition grindstone can be unified, the shape change of the electrodeposition grindstone can be stabilized, and the life of the electrodeposition grindstone can be extended. For this reason, the frequency | count of replacement | exchange of an electrodeposition grindstone can be reduced, As a result, work efficiency can be improved and productivity can be improved. Furthermore, by performing dressing by automatic dressing in this manner, dummy processing is unnecessary, so that productivity is not reduced and it is not necessary to waste a glass substrate used for dummy processing.

  In the method for manufacturing a glass substrate for a magnetic disk according to the present invention, the chamfering step has the same shape along the shape of the end surface and the chamfer surface, and the roughness of the eyes is different. It is preferable to chamfer using an electrodeposition grindstone.

  The electrodeposition grindstone of the present invention is an electrodeposition grindstone used for chamfering for forming a chamfer surface between the pair of main surfaces and the end surfaces of a glass substrate having a pair of main surfaces and end surfaces, respectively. Chamfering is performed by using electrodeposition grindstones having the same shape along the shape of the end surface and the chamfer surface and having different eye roughness.

  According to this configuration, since the shape of the electrodeposition grindstone can be unified, the shape change of the electrodeposition grindstone can be stabilized, and the life of the electrodeposition grindstone can be extended. For this reason, the frequency | count of replacement | exchange of an electrodeposition grindstone can be reduced, As a result, work efficiency can be improved and productivity can be improved.

  The method for manufacturing a glass substrate for a magnetic disk according to the present invention is automatically dressed in a chamfering step of forming a chamfer surface between the pair of main surfaces and the end surfaces of a glass substrate having a pair of main surfaces and end surfaces. Therefore, it is highly productive and does not cause chipping. Moreover, according to this method, the lifetime of an electrodeposition grindstone can be lengthened.

It is a figure which shows the chamfering processing apparatus used for the manufacturing method of the glass substrate for magnetic discs concerning embodiment of this invention. It is a figure which shows the relationship between an electrodeposition grindstone and the glass substrate for magnetic discs. (A)-(c) is a figure for demonstrating the truing and dressing of an electrodeposition grindstone.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As a material for the glass substrate for magnetic disk, aluminosilicate glass, soda lime glass, borosilicate glass and the like can be used. In particular, aluminosilicate glass can be preferably used in that it can be chemically strengthened and can provide a glass substrate for a magnetic disk excellent in flatness of the main surface and substrate strength.

  The manufacturing process of the magnetic disk substrate includes a material processing step and a first grinding step; an end shape step (coring step for forming a hole, a chamfered surface at the end (outer peripheral end and / or inner peripheral end) Chamfering step to be formed (chamfered surface forming step)); end surface polishing step (outer peripheral edge and inner peripheral edge); second grinding step; main surface polishing step (first and second polishing step); chemical strengthening step, etc. These steps are included.

Below, each process of the manufacturing process of the board | substrate for magnetic discs is demonstrated. Here, a case where the magnetic disk substrate is a glass substrate will be described.
(1) Material processing step and first grinding step First, in the material processing step, a glass base material (blanks) serving as a glass substrate is made of, for example, molten glass using a press method, a float method, a down draw method, a redraw method. It can be produced using a known production method such as a fusion method. Of these methods, if a press method is used, a sheet glass can be produced at a low cost.

  In the first grinding step, both main surfaces of the sheet glass are ground to form a disk-shaped glass substrate. This grinding process can be performed using alumina-based loose abrasive grains by a double-side grinding apparatus using a planetary gear mechanism. Specifically, the lapping platen is pressed from above and below on both sides of the plate glass, a grinding liquid containing free abrasive grains is supplied onto the main surface of the plate glass, and these are moved relatively to perform grinding processing. Do. By this grinding process, a glass substrate having a flat main surface can be obtained.

(2) End shape process (coring process for forming a hole, chamfering process for forming a chamfer on the end (outer peripheral end and inner peripheral end) (chamfered surface forming process))
In the coring step, for example, an inner hole is formed at the center of the glass substrate using a cylindrical diamond drill to obtain an annular glass substrate. In the chamfering step, the inner peripheral end surface and the outer peripheral end surface are ground with a diamond grindstone, and a predetermined chamfering process is performed.

  FIG. 1 is a diagram showing a chamfering apparatus used in a method for manufacturing a glass substrate for a magnetic disk according to an embodiment of the present invention. The chamfering apparatus shown in FIG. 1 performs chamfering on the outer peripheral side electrodeposition grindstone 1 that performs chamfering on the outer peripheral side of the annular magnetic disk glass substrate 5 and on the inner peripheral side of the magnetic disk glass substrate 5. An inner circumference side electrodeposition grindstone 3 is provided. The outer peripheral side electrodeposited grindstone 1 is configured to be rotationally driven, lifted and lowered and horizontally driven by the outer peripheral side electrodeposited grindstone driving unit 2. The inner circumference side electrodeposition grindstone 3 is configured to be rotationally driven, lifted and lowered and horizontally driven by the inner circumference side electrodeposition grindstone driving unit 4.

  The outer periphery side electrodeposition grindstone 1 has a fine outer periphery side electrodeposition grindstone 1a and a coarse outer periphery side electrodeposition grindstone 1b, and both electrodeposition grindstones 1a and 1b are laminated. The inner circumference side electrodeposition grindstone 3 also includes a fine inner circumference side electrodeposition grindstone 3a and a coarse inner circumference side electrodeposition grindstone 3b, and both the electrodeposition grindstones 3a and 3b are laminated.

  Each of the fine outer peripheral side electrodeposition grindstone 1a and the coarse outer peripheral side electrodeposition grindstone 1b has a shape as shown in FIG. The fine outer peripheral electrodeposition grindstone 1a and the coarse outer peripheral electrodeposition grindstone 1b have an upper chamfer surface contact surface 11, an end surface contact surface 12, and a lower chamfer surface contact surface 13. The upper chamfer surface abutting surface 11 is a surface on which the upper chamfer surface 54 is formed by grinding the glass substrate 5 for magnetic disk having the pair of main surfaces 51 and 52 and the end surface 53. The end surface contact surface 12 is a surface on which the end surface 53 is formed by grinding the magnetic disk glass substrate 5. The lower chamfer surface abutting surface 13 is a surface on which the lower chamfer surface 55 is formed by grinding the magnetic disk glass substrate 5.

  Moreover, the fine outer peripheral side electrodeposition grindstone 1a and the coarse outer peripheral side electrodeposition grindstone 1b have different roughness of eyes. For example, the fine outer peripheral side electrodeposition grindstone 1a has a coarseness of about 500 counts, and the coarse outer peripheral side electrodeposition grindstone 1b has a coarseness of about 325 counts. In addition, about the coarseness of the fine outer periphery side electrodeposition grindstone 1a and the coarse outer periphery side electrodeposition grindstone 1b, it is not limited to this, It can change suitably.

  That is, the fine outer peripheral side electrodeposition grindstone 1a and the coarse outer peripheral side electrodeposition grindstone 1b have the same shape along the shapes of the end surface 53 and the chamfer surfaces 54 and 55 of the magnetic disk glass substrate 5, respectively. , Each has a different roughness. Further, the fine inner circumference side electrodeposition grindstone 3a and the coarse inner circumference side electrodeposition grindstone 3b have the same shape along the shapes of the end face 53 and the chamfer surfaces 54 and 55 of the glass substrate 5 for magnetic disks, respectively. And the roughness of each eye is different.

  The fine electrodeposition grindstones 1a and 3a and the coarse electrodeposition grindstones 1b and 3b are produced by electrodepositioning diamond abrasive grains on a base material and then dressing by automatic dressing. By performing dressing by automatic dressing in this way, the quality of the abrasive grain shape can be stabilized, so that chipping in chamfering can be eliminated. Further, since the shape of the electrodeposition grindstone can be unified, the shape change of the electrodeposition grindstone can be stabilized, and the life of the electrodeposition grindstone can be extended. For this reason, the frequency | count of replacement | exchange of an electrodeposition grindstone can be reduced, As a result, work efficiency can be improved and productivity can be improved. Furthermore, by performing dressing by automatic dressing in this manner, dummy processing is unnecessary, so that productivity is not reduced and it is not necessary to waste a glass substrate used for dummy processing.

(3) 2nd grinding process In a 2nd grinding process, the 2nd grinding process is performed about the both main surfaces of the obtained glass substrate similarly to a 1st grinding process. By performing this second grinding step, the fine irregularities / surface damage / scratches formed on the main surface in the previous step are removed, and the surface roughness is further reduced as compared with the first grinding. It becomes possible to complete the polishing process for the main surface in a short time.

(4) End surface polishing step In the end surface polishing step, the outer peripheral end surface and the inner peripheral end surface of the glass substrate are mirror-polished by a brush polishing method. At this time, as the abrasive grains, for example, a slurry containing cerium oxide abrasive grains (free abrasive grains) can be used. By removing the contamination, damage, and scratches on the end surface of the glass substrate by this end surface polishing step, it becomes possible to prevent the occurrence of ion precipitation that causes corrosion such as sodium and potassium.

(5) Main surface polishing step (first polishing step)
As the main surface polishing step, first, a first polishing step is performed. In the main surface polishing process, for example, a polishing apparatus using a planetary gear mechanism is used. The first polishing process is a process whose main purpose is to remove scratches and distortions remaining on the main surface in the lapping process described above. In the first polishing step, the main surface is polished using a hard resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, cerium oxide abrasive grains can be used.

(6) Main surface polishing step (final polishing step)
Next, a second polishing process is performed as a final polishing process. A 2nd grinding | polishing process is a process aiming at finishing only the surface used as a recording surface among both main surfaces in a mirror surface shape. Also in the second polishing step, the main surface is mirror-polished using a soft foamed resin polisher by a double-side polishing apparatus having a planetary gear mechanism in the same manner as described above. As the slurry, cerium oxide abrasive grains or colloidal silica finer than the cerium oxide abrasive grains used in the first polishing step can be used.

(7) Chemical strengthening step In the chemical strengthening step, the glass substrate that has been subjected to the lapping step and polishing step described above is chemically strengthened. As a chemical strengthening solution used for chemical strengthening, for example, a mixed solution of potassium nitrate (60%) and sodium nitrate (40%) can be used. In the chemical strengthening, the chemical strengthening solution is heated to 300 ° C. to 400 ° C., the cleaned glass substrate is preheated to 200 ° C. to 300 ° C., and immersed in the chemical strengthening solution for 3 hours to 4 hours. In soaking, in order to chemically strengthen the entire surface of the glass substrate, the immersion is preferably performed in a state of being accommodated in a holder so that the plurality of glass substrates are held at the end surfaces.

  Thus, by immersing in the chemical strengthening solution, the lithium ions and sodium ions in the surface layer of the glass substrate are respectively replaced with sodium ions and potassium ions having a relatively large ion radius in the chemical strengthening solution. Will be strengthened.

Next, examples performed for clarifying the effects of the present invention will be described.
(Example)
First, the melted aluminosilicate glass was molded into a disk shape by direct pressing using an upper mold, a lower mold, and a barrel mold to obtain an amorphous plate glass material (blanks). At this point, the diameter of the blanks was 66 mm. Next, both main surfaces of the blanks were subjected to a first lapping process, and then a cylindrical core drill was used to form a hole in the center of the glass substrate to process it into an annular glass substrate (coring). . And the chamfering process (chamfering surface formation process) which forms a chamfering surface in the edge part (an outer peripheral edge part and an inner peripheral edge part) was given, and it was set as the glass substrate of diameter 2.5 inches. At this time, the processing apparatus shown in FIG. 1 was used for chamfering. In addition, the electrodeposition grindstone has the same shape along the shape of the end surface and the chamfer surface of the glass substrate, each dressed by automatic dressing, and has two different roughnesses of the eyes. An electrodeposition grindstone was used.

  With respect to 100 glass substrates subjected to chamfering in this manner, the roundness was determined by a round tester (Mitutoyo_RA-300), and the variation was determined to be 0.5 μm to 1.5 μm. Moreover, the electrodeposition grindstone dressed by automatic dressing did not change its shape even after processing 13,000 sheets, and a glass substrate with a desired roundness could be obtained.

(Comparative example)
In the chamfering process, the same procedure as in the example was performed except that two electrodeposition grindstones having different shapes and dressed by dressing by skilled workers were used. Chamfering (chamfered surface forming process) was applied. For 100 glass substrates that were chamfered in this manner, the roundness was determined in the same manner as in the example, and the variation was determined to be 0.7 μm to 2.5 μm. In addition, the electrodeposition grindstone changed its shape when 9,000 pieces were processed, and the desired roundness could not be obtained.

  In addition, this invention is not limited to the said embodiment, It can implement by changing suitably. The numerical values, materials, sizes, processing procedures, and the like in the above-described embodiment are merely examples, and various modifications can be made within the scope of the effects of the present invention. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  The present invention is applicable to devices equipped with various HDDs, such as personal computers and portable music devices.

DESCRIPTION OF SYMBOLS 1 Outer peripheral side electrodeposition grindstone 1a Fine outer peripheral side electrodeposition grindstone 1b Coarse outer peripheral side electrodeposition grindstone 2 Outer peripheral side electrodeposition grindstone driving part 3 Inner peripheral side electrodeposition grindstone 3a Fine inner peripheral side electrodeposition grindstone 3b Rough inner peripheral side electrodeposition Grinding wheel 4 Inner peripheral electrodeposited grinding wheel drive unit 5 Magnetic disk glass substrate 11 Upper chamfer surface abutting surface 12 End surface abutting surface 13 Lower chamfer surface abutting surface 51, 52 Pair of main surfaces 53 End surface 54 Upper chan Fur side 55 Lower chamfer side

Claims (3)

  A method of manufacturing a magnetic disk substrate comprising a chamfering step of forming a chamfer surface between the pair of main surfaces and the end surface of a glass substrate having a pair of main surfaces and end surfaces, the chamfering step A method for producing a glass substrate for a magnetic disk, wherein chamfering is performed using an automatically dressed electrodeposition grindstone.   In the chamfering step, chamfering is performed by using an electrodeposition grindstone having the same shape along the shape of the end surface and the chamfer surface, respectively, and having different eye roughness. The method for producing a glass substrate for a magnetic disk according to claim 1.   An electrodeposition grindstone used for chamfering that forms a chamfer surface between the pair of main surfaces and the end surface of a glass substrate having a pair of main surfaces and end surfaces, each having a shape of the end surface and the chamfer surface The electrodeposition grindstone is characterized in that chamfering is performed by using an electrodeposition grindstone having the same shape along the surface and having different eye roughness.

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