JP2009015914A - Manufacturing method of glass substrate for magnetic disk, manufacturing apparatus, and manufacturing method of magnetic disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately polish an inner peripheral end surface while the number of layered glass substrates is secured and to enhance tolerance and roundness of inner holes. <P>SOLUTION: A bottom wall part 19 of a holder body 17 of a work holder is attached onto a table 5, a plurality of glass substrates 2 are layered on the bottom wall part 19, the glass substrates 2 are positioned on the bottom wall part 19 by providing a shaft 12 on the bottom wall part 19 in an erected state so that the shaft 12 penetrates through the communicating inner holes of the layered glass substrates 2, the positioned glass substrates 2 are pushed and fixed from an upper part by a pushing part 22 of a holder cover 18 of the work holder, then the shaft 12 is removed from the communicating inner holes of the glass substrates 2 and a polishing brush is inserted in the inner holes to polish the inner holes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for manufacturing a glass substrate for a magnetic disk, and a method for manufacturing a magnetic disk using the glass substrate manufactured by these, and more specifically, the inner peripheral end surface of an inner hole formed in the glass substrate. It relates to polishing technology.

  In recent years, with the advancement of information technology, information recording technology, particularly magnetic recording technology, has made remarkable progress. An aluminum substrate has been widely used as a substrate for a magnetic recording medium such as an HDD (Hard Disk Drive) which is one of the magnetic recording media. However, with the miniaturization, thinning, and high-density recording of magnetic disks, glass substrates that are superior in substrate surface flatness and substrate strength compared to aluminum substrates are gradually being replaced.

  As the magnetic recording technology has been increased in density, the magnetic head has been changed from a thin film head to a magnetoresistive head (MR head) and a large magnetoresistive head (GMR head). The flying height of this is narrowing to about 8 nm. For this reason, there may be a crash failure that the magnetic head collides due to the uneven shape on the magnetic disk surface, or a thermal asperity failure that causes a read error due to adiabatic compression of air or heating due to contact between the magnetic head and the magnetic disk. . Under the circumstances as described above, the importance of the smoothness of the end face of the substrate has been recognized conventionally. In Patent Document 1, it is said that by polishing each end face of the outer periphery and inner periphery of the substrate up to a mirror surface, generation and adsorption of particles on the end face of the substrate can be prevented, and the above problem can be solved.

As a technique for polishing the inner peripheral end face of the glass substrate, a polishing method using a rotating brush as described in Patent Document 2 is known. In this polishing method, a disk-shaped glass substrate having an inner hole is stacked and accommodated in a substrate case and a tightening cover (work holder), which is fixed to a rotation holding table (table), and then the glass substrate is communicated. The inner peripheral end face is polished by inserting a rotating brush into the inner hole and rotating the rotating holding base and the rotating brush while being immersed in the polishing liquid.
JP-A-10-154321 JP-A-11-221742

  Recently, in order to further improve the recording density, a perpendicular magnetic recording system is being adopted. In the case of this perpendicular magnetic recording medium, the influence of the glass substrate tends to appear more conspicuously than in the case of the in-plane magnetic recording system. For this reason, the glass substrate is required to have lower roughness, flatness, and shape accuracy. In particular, the rotational speed of the magnetic disk tends to increase in order to improve the reading speed of the HDD, and the center of gravity of the rotation of the magnetic disk is extremely important, so the dimensional tolerance of the inner hole (inner peripheral end face) is small. A high roundness, and therefore a small tolerance for fitting with the spindle is required.

  On the other hand, in recent years, there has been a demand for a small HDD to be mounted especially on mobile phones, digital cameras, portable music players, etc., and magnetic disks are required to be further miniaturized, higher recording density and lower cost. ing.

  Here, in order to reduce the production cost in polishing the inner peripheral end face of the glass substrate, it is conceivable to increase the number of sheets to be laminated at the time of polishing. For example, if 300 sheets are laminated and polished every 300 sheets, it is possible to simply produce with 1/3 tact (processing time). However, as the number of stacked layers increases, the tolerance and roundness of the inner hole tend to decrease.

  Accordingly, the present invention provides a method and apparatus for manufacturing a glass substrate for a magnetic disk, which can polish the inner peripheral end face with high accuracy while ensuring the number of laminated glass substrates, and improve tolerance and roundness of the inner hole. An object of the present invention is to provide a method of manufacturing a magnetic disk using a glass substrate manufactured by these methods.

  The inventor of the present invention diligently studied the above problem, and as a result, when the laminated glass substrates are inclined with respect to the rotation axis when polishing the inner peripheral end face, the tolerance and roundness of the inner hole are lowered. I found out. And, as a result of examining the polishing process to solve this problem, the degree of coincidence between the axis of the inner hole and the rotation axis increases as the number of glass substrates increases in the stage of stacking and holding the glass substrates on the work holder. The present inventors have found out that even if the glass substrate can be held on the work holder with high accuracy, the inclination tends to occur when the work holder is set on the table. Then, after setting the work holder on the table, by setting the glass substrate on the work holder, it is found that the degree of coincidence between the axis of the inner hole and the rotation axis can be improved, and the present invention is completed. It came.

  That is, in order to solve the above problems, a typical configuration of the method for manufacturing a glass substrate for a magnetic disk according to the present invention is to laminate a glass substrate having an inner hole and insert a polishing body into the communicating inner hole for polishing. In the method for manufacturing a glass substrate for a magnetic disk including the inner peripheral end face polishing step, the positioning member has a central axis that coincides with the central axis of the polishing body instead of the polishing body at a position where the polishing body of the polishing apparatus is attached. Mounting step, a step of laminating a plurality of glass substrates, a step of penetrating through an inner hole of a glass substrate laminated with a positioning member, a step of fixing the laminated glass substrate, and a positioned glass substrate Removing the positioning member from the communicating inner hole, attaching the polishing body to the polishing apparatus instead of the positioning member, and communicating the inner hole of the positioned glass substrate Characterized in that it comprises a step of inserting the abrasive body.

  According to the said structure, the glass substrate laminated | stacked by the positioning member of the exact same position and attitude | position as a grinding | polishing body can be positioned by attaching a positioning member to the position which attaches the grinding | polishing body of the grinding | polishing apparatus which grind | polishes an inner peripheral end surface. . For this reason, even if the number of laminated glass substrates is large, the inner peripheral end face of each glass substrate can be polished with high accuracy, and the tolerance, roundness, and concentricity of the inner holes can be improved.

  Another typical configuration of the method for manufacturing a glass substrate for a magnetic disk according to the present invention is to laminate a plurality of glass substrates on a table of a polishing apparatus for polishing an inner peripheral end surface of an inner hole formed in the glass substrate. Attaching the lower holding part of the work holder sandwiched between the upper holding part and the lower holding part in a state, the step of laminating a plurality of glass substrates on the lower holding part, and the glass laminated on the lower holding part The step of installing the shaft in an upright state with respect to the lower holding portion, the step of positioning the glass substrate laminated by the shaft, and the positioning on the lower holding portion so as to penetrate the inner hole communicated with the substrate Pressing the glass substrate from above with the upper holding portion, removing the shaft from the communicating inner hole of the positioned glass substrate, and inserting the polishing body into the communicating inner hole of the positioned glass substrate A step of entering, characterized in that it comprises a step of polishing by the polishing body inner peripheral edge surface by relatively rotating or moving the table and the polishing body.

  In the present invention, the top and bottom do not necessarily correspond to the direction of gravity, and the far side as viewed from the table may be up and the near side may be down. The connecting portion between the lower holding portion and the upper holding portion may be a position that does not hinder the work. When the lower holding portion is mounted on the table, some member or the like may be interposed between the two, and the shaft upright state only needs to be accurate enough to position the glass substrate by the shaft. At the time of polishing the inner peripheral end surface by the polishing body, the table and the polishing body are relatively rotated or moved. “Relative” means that either or both of the table and the polishing body are driven and the polishing body is moved to the inner peripheral end surface. Means that the polishing body reciprocates in a direction substantially perpendicular to the table (in the axial direction of the inner hole), for example. including.

  According to the above configuration, the lower holding portion of the work holder is mounted on the table, a plurality of glass substrates are stacked on the lower holding portion, and the lower holding is performed so as to penetrate through the inner holes communicated with the stacked glass substrates. The glass substrate is positioned on the lower holding part by installing the shaft in an upright state with respect to the part, and the glass substrate is communicated with the upper side holding part by pressing and fixing the positioned glass substrate from above. The shaft is removed from the hole, and the polishing body is inserted into the inner hole for polishing. Therefore, the glass substrate is positioned and fixed immediately before polishing, and the tolerance and roundness of the inner hole are improved. Can do. That is, the shaft is pulled out between the positioning / fixing stage and the polishing stage of the glass substrate, but this pulling process shifts the overlap between the positioned and fixed glass substrates (inner holes) in the radial direction. Therefore, the position of the glass substrate relative to the table is not disturbed. In addition, when the work holder is fixed on the table after the laminated glass substrate is accommodated in the work holder, the accuracy of mounting the work holder on the table decreases due to, for example, abrasive grains entering between the work holder and the table. However, there is a concern that the positioning accuracy of the glass substrate with respect to the table may be lowered. However, in the above configuration, the work holder is attached to the table in advance (before holding the glass substrate). Even if there is some problem in the mounting accuracy with respect to the table, the error can be absorbed in the glass substrate positioning step performed thereafter.

  The shaft may be expandable / contractable in the radial direction, and in the step of positioning the glass substrate laminated by the shaft, the shaft is expanded in the radial direction to perform positioning, and the shaft is removed from the inner hole communicated with the positioned glass substrate. In the removal process, the shaft may be contracted in the radial direction and removed. Thereby, it is possible to prevent an excessive force from being applied to the glass substrate due to the reduced diameter of the shaft when the shaft is removed, and it is possible to perform positioning with high accuracy by expanding the diameter of the shaft when positioning the glass substrate. .

  In the above configuration, the step of laminating a plurality of glass substrates on the lower holding portion is accommodated in a step of accommodating a plurality of glass substrates in a state where a plurality of glass substrates are laminated on a bottomed cylindrical work cover opened upward, and being accommodated in the work cover. And a step of installing the glass substrate together with the work cover on the lower holding portion. In the present invention, the cylindrical shape of the work cover may not be entirely constituted by the wall body, but may be constituted by a frame body or the like having a cylindrical shape as a whole. By using the work cover in this manner, the glass substrate can be easily set on the work holder in which the lower holding portion is fixed to the table.

  A representative configuration of a magnetic disk glass substrate manufacturing apparatus according to the present invention includes a work holder that is sandwiched between an upper holding portion and a lower holding portion in a state in which a plurality of glass substrates having inner holes are stacked, and a lower side. A shaft provided with a table to which the holding portion is attached, a shaft that can be expanded and contracted in the radial direction, and a polishing body attachment portion to which a polishing body that polishes the inner peripheral end surface of the inner hole by relative rotation or movement with the table is attached. However, when multiple glass substrates are stacked on the lower holding part attached to the table, it can be installed upright with respect to the table so that the glass substrate is positioned by extending through the inner hole and expanding in the radial direction. In addition, the positioned glass substrate can be removed from the inner hole by shrinking in the radial direction with the upper holding portion pressed from above, and the polishing body attached to the polishing body mounting portion is Shift is inserted into the inner hole after being pulled out from the inner hole of the glass substrate positioned, characterized by polishing the inner peripheral end surface.

  According to the above configuration, the lower holding portion of the work holder is mounted on the table, a plurality of glass substrates are stacked on the lower holding portion, and the lower holding is performed so as to penetrate through the inner holes communicated with the stacked glass substrates. The glass substrate is positioned on the lower holding part by installing the shaft in an upright state with respect to the part, and the glass substrate is communicated with the upper side holding part by pressing and fixing the positioned glass substrate from above. By removing the shaft from the hole and inserting a polishing body into the inner hole for polishing, the glass substrate is positioned and fixed immediately before polishing, improving the tolerance and roundness of the inner hole. be able to. Further, it is possible to prevent an excessive force from being applied to the glass substrate due to the reduced diameter of the shaft when the shaft is removed, and positioning can be performed with high accuracy by expanding the shaft when positioning the glass substrate.

  This manufacturing apparatus has a bottomed cylindrical shape that opens upward, and includes a work cover that accommodates a plurality of glass substrates stacked together. The glass substrate accommodated in the work cover is placed on the lower holding portion together with the work cover. It may be configured to be installed. By using such a work cover, the glass substrate can be easily set to the work holder in which the lower holding portion is fixed to the table.

  A typical configuration of the method of manufacturing a magnetic disk according to the present invention includes an upper holding portion in a state where a plurality of glass substrates are stacked on a table of a polishing apparatus for polishing an inner peripheral end surface of an inner hole formed in a glass substrate. A step of attaching the lower holding part of the work holder sandwiched by the lower holding part, a step of laminating a plurality of glass substrates on the lower holding part, and an internal hole of the glass substrate laminated on the lower holding part A step of installing the shaft in an upright state with respect to the lower holding portion, a step of positioning the glass substrate laminated by the shaft, and an upper holding of the glass substrate positioned on the lower holding portion. A step of pressing from above, a step of removing the shaft from the communicating inner hole of the positioned glass substrate, a step of inserting an abrasive body into the communicating inner hole of the positioned glass substrate, and a table And a step of polishing bodies are relatively rotated or moved to polish the inner peripheral end surface by the polishing body, after the glass substrate is polished, characterized in that it comprises a step of forming a magnetic layer on the surface thereof.

  According to the above configuration, the lower holding portion of the work holder is mounted on the table, a plurality of glass substrates are stacked on the lower holding portion, and the lower holding is performed so as to penetrate through the inner holes communicated with the stacked glass substrates. The glass substrate is positioned on the lower holding part by installing the shaft in an upright state with respect to the part, and the glass substrate is communicated with the upper side holding part by pressing and fixing the positioned glass substrate from above. The shaft is removed from the hole, and the polishing body is inserted into the inner hole for polishing. Therefore, the glass substrate is positioned and fixed immediately before polishing, and the tolerance and roundness of the inner hole are improved. Can do.

  The shaft may be expandable / contractable in the radial direction, and in the step of positioning the glass substrate laminated by the shaft, the shaft is expanded in the radial direction to perform positioning, and the shaft is removed from the inner hole communicated with the positioned glass substrate. In the removal process, the shaft may be contracted in the radial direction and removed. Thereby, it is possible to prevent an excessive force from being applied to the glass substrate due to the reduced diameter of the shaft when the shaft is removed, and it is possible to perform positioning with high accuracy by expanding the diameter of the shaft when positioning the glass substrate. .

  In the above configuration, the step of laminating a plurality of glass substrates on the lower holding portion is accommodated in a step of accommodating a plurality of glass substrates in a state where a plurality of glass substrates are laminated on a bottomed cylindrical work cover opened upward, and being accommodated in the work cover. And a step of installing the glass substrate together with the work cover on the lower holding portion. By using the work cover in this manner, the glass substrate can be easily set on the work holder in which the lower holding portion is fixed to the table.

  According to the present invention, even when the number of laminated glass substrates is large, the inner peripheral end face of each glass substrate can be polished with high accuracy, and the tolerance, roundness, and concentricity of the inner holes can be improved. .

  The best mode for carrying out the present invention will be described with reference to the drawings.

  1 is a sectional view showing a polishing apparatus (manufacturing apparatus) for a glass substrate for a magnetic disk, FIG. 2 is a plan view showing a table, FIG. 3 is a plan view showing a holder body of a work holder, and FIG. 4 is a cross section showing a work cover. 5 is a side view showing the shaft, FIG. 6 is an explanatory view showing a procedure for attaching the holder body, FIG. 7 is an explanatory view showing a procedure for holding the laminated glass substrate on the work holder, and FIG. FIG. 9 is a flowchart showing a polishing method by a polishing apparatus, FIG. 10 is an explanatory diagram showing a shaft that can be expanded and contracted, and FIG. 11 is a diagram showing a method of holding a glass substrate laminated using a shaft that can be expanded and contracted on a work holder. FIG. 12 is an explanatory view showing another example of an expandable / contractible shaft. The specific dimensions, shapes, materials, and other numerical values shown in the following embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. .

  As shown in FIG. 1, a magnetic disk glass substrate polishing apparatus 1 polishes an inner peripheral end surface 3a of a cylindrical object 3 formed by laminating glass substrates 2, and includes a base 4 and a table 5. And a work holder 6, a work cover 7, a tool shaft 8, a drive motor 9, a polishing brush 10, a nozzle 11, and a shaft 12 (see FIG. 5) as an example of a positioning member.

  The object to be polished 3 is formed by alternately laminating a plurality (for example, 300) of glass substrates 2 with annular spacers 13 made of a nonwoven fabric or the like. The glass substrate 2 has an inner hole formed at the center of the disk-shaped glass, and the outer peripheral end face and the inner peripheral end face 2a of the inner hole are chamfered (in FIG. 1, reference numerals 2b and 2c are inner peripheral end faces 2a). Shows the chamfered part.) The spacer 13 is provided in order to reliably prevent the polishing residue of the chamfered portion of the glass substrate 2 and damage during polishing. The inner hole (in-cylinder space) of the object to be polished 3 is formed by communicating with the inner hole of the glass substrate 2, and the inner peripheral end face 3 a of the object to be polished 3 is formed by the inner peripheral end face 2 a of the glass substrate 2 (with the spacer 13 interposed). However, it is composed continuously.

  The base 4 is installed on a horizontal plane, and the table 5 is rotatably supported by the base 4 via a bearing 14. As shown in FIG. 2, the table 5 has a circular shape in a plan view, and is driven by a driving device (not shown) to rotate in an arbitrary direction on the horizontal plane.

On the upper surface 5a of the table 5, screw holes 15 are provided at positions (positions every 120 °) that divide the circumference into three equal parts on the circumference of the radius r ₁ centering on the rotation axis O ₁ . . A jig 16, which will be described later, can be detachably attached to the outer peripheral surface 5b of the table 5.

  The work holder 6 includes a holder main body 17 and a holder cover 18. The holder body 17 includes a bottom wall portion 19 that is circular in plan view, a cylindrical peripheral wall portion 20 that stands up from the outer edge of the bottom wall portion 19, and a flange portion that extends radially outward from the lower portion of the peripheral wall portion 20. 21 is integrally formed. The holder cover 18 includes an annular pressing portion 22 and a peripheral wall portion 23 extending downward from the outer edge of the pressing portion 22. For example, the holder cover 18 forms a male screw on the upper outer peripheral surface 20 a of the peripheral wall portion 20. By forming a female screw on the inner peripheral surface 23a of 23 and screwing the male screw and the female screw together, the holder cover 18 is attached and fixed on the peripheral wall portion 20 as a lid body of the holder main body 17. ing.

At the center of the bottom wall portion 19 of the holder main body 17, as shown in FIG. 3, a through portion 24 that penetrates the bottom wall portion 19 up and down is provided. The penetrating portion 24 is generally configured by an inverted conical concave portion 26 corresponding to the shape of the tapered portion 25 (see FIG. 5) of the shaft 12 and a circular hole 27 communicating with the concave portion 26 arranged vertically. The flange portion 21 is slightly more than the screw hole 15 at a position that divides the circumference into three equal parts on the circumference of the radius r ₂ (r ₂ = r ₁ ) centered on the axis O ₂ of the circular hole 27. A large-diameter insertion hole 28 is provided. A screw hole 29 is provided at a position equidistant from the adjacent insertion hole 28 on the same circumference. A jig 30 described later can be detachably attached to the outer peripheral surface 21 a of the flange portion 21. The holder main body 17 is attached to the upper surface 5 a of the table 5 by screwing the tip of the knurled bolt 31 inserted through the insertion hole 28 into the screw hole 15.

  As shown in FIG. 4, the work cover 7 includes a cylindrical metal tube 32 made of a metal such as stainless steel and an annular resin ring 33 made of a resin such as polyacetal. The metal cylinder 32 has a bent portion 34 that is bent inward at the lower end thereof, and the resin ring 33 is locked to the bent portion 34, whereby the work cover 7 as a whole has an insertion hole 35 (resin An inner hole) of the ring 33 is formed and has a bottomed cylindrical shape opened upward.

  The object to be polished 3 is accommodated inside the metal tube 32 of the work cover 7 and set together with the work cover 7 on the bottom wall portion 19 of the holder body 17. An annular spacer 36 made of resin such as polyacetal is placed on the object to be polished 3, and is pressed from above by the pressing portion 22 of the holder cover 18 through the spacer 36. The workpiece holder 6 is held between the wall portion 19 and the pressing portion 22.

The tool shaft 8 is arranged above the table 5 and is driven by a drive motor 9 to rotate in any direction forward and reverse concentric with the rotation axis O ₁ of the table 5. The tool shaft 8 and the drive motor 9 are driven up and down by a lifting device (not shown).

  The polishing brush 10 is detachably attached to the tool shaft 8 and passes through the inner hole of the object to be polished 3, and the lower end thereof reaches the vicinity of the recess 26 of the holder body 17. The lower end side of the polishing brush 10 may be pivotally supported by the base 4 or the like through the bottom wall portion 19 or the table 5 of the work holder 6 and thus supporting the polishing brush from the lower side. Therefore, it is possible to improve the polishing accuracy by preventing the shaking of the polishing brush during polishing.

  The nozzle 11 is provided so as to face the tool shaft 8 and supplies the polishing liquid from above the polishing brush 10. The supplied polishing liquid flows down between the polishing brush 10 and the inner peripheral end surface 3a of the object 3 to be polished, passes through the through portion 24, and is collected in a drain port (not shown).

  As shown in FIG. 5, the shaft 12 has a substantially cylindrical shape and is provided in the work holder 6 instead of the polishing brush 10 to serve for positioning of the glass substrate 2 constituting the object to be polished 3 as described later. The shaft 12 is attached to the tool shaft 8, an attachment portion 37, a columnar large-diameter shaft portion 38 that is formed continuously with the attachment portion 37 and has substantially the same diameter as the inner hole of the glass substrate 2, and a large diameter. A tapered portion 25 continuously formed on the shaft portion 38 and having a diameter reduced toward the lower side, and a columnar small-diameter shaft portion 39 formed continuously with the tapered portion 25 and having substantially the same diameter as the circular hole 27; Is provided.

  In order to polish the object 3 using the polishing apparatus 1, first, the holder body 17 of the work holder 6 is attached to the upper surface 5 a of the table 5.

  As shown in FIGS. 6 and 9, the knurled bolt 31 is inserted into the insertion hole 28 of the flange portion 21, and the tip end portion is temporarily fixed to the screw hole 15 of the table 5 (step 401 (“S. 401 ”. The same applies hereinafter))), and the knurled bolt 40 is screwed into the screw hole 29 of the flange portion 21, and the amount of protrusion of the knurled bolt 40 from the lower surface 21a of the flange portion 21 is adjusted. Make it horizontal. Specifically, the gauge 41 for measuring displacement is attached to the tool shaft 8, the stylus 42 of the gauge 41 is applied to the bottom wall portion 19, and the three pieces of the gauge 41 show a constant value while rotating the table 5 at a low speed. The knurled bolt 40 is moved forward and backward along the screw hole 29. When the tips of the three knurled bolts 40 come into contact with the upper surface 5a of the table 5 in a well-balanced manner, the indicated value of the gauge 41 becomes constant regardless of the rotation of the table 5, and the tilt adjustment of the holder body 17 is completed (step) 402, FIG. 6 (A)).

Then, the jig 16 attached to the two positions of the outer circumferential surface 5b of the table 5 (preferably attached to position two straight lines connecting the rotation axis O ₁ and each mounting portion is orthogonal in plan view.), Flange 21 two places of the outer peripheral surface 21a of the (attachment point of the jig 16 across the rotation axis O ₁ and the opposite-side position) attaching the jig 30. As a method of attaching the jigs 16 and 30, for example, it is conceivable to magnetically attach to the outer peripheral surfaces 5b and 21a.

  The jig 16 protrudes above the upper surface 5 a of the table 5, and a screw hole 43 is formed in the protruding portion along the horizontal direction. A knurled bolt 44 is screwed into the screw hole 43. On the other hand, the jig 30 has an L shape extending in the horizontal direction from the outer peripheral surface 21a of the flange portion 21 and bending downward, and a screw hole 45 is formed along the horizontal direction in the downward bent portion. The knurled bolt 46 is screwed into the screw hole 45.

Here, the holder main body 17 is only temporarily fixed to the table 5, and the insertion hole 28 is slightly larger in diameter than the screw hole 15, and only the amount of play between the insertion hole 28 and the knurled bolt 31 is achieved. Since there is room for the holder body 17 to move in the horizontal direction, when the knurled bolts 44 and 46 are advanced and retracted along the screw holes 43 and 45, the tips of the knurled bolts 44 and 46 come into contact with the outer peripheral surfaces 21a and 5b. The holder body 17 is moved horizontally. Using this fact, the knurled bolts 44 and 46 are advanced and retracted to adjust the amount of protrusion of each knurled bolt from the jig, and the position of the holder body 17 is adjusted so that the axis O ₂ coincides with the rotation axis O _1. adjust. That is, the stylus 42 of the gauge 41 attached to the tool shaft 8 is applied to the concave portion 26, and the two sets of knurled bolts 44 and 46 are advanced and retracted so that the gauge 41 shows a constant value while rotating the table 5 at a low speed. When the tips of the knurled bolts 44 and 46 come into contact with the outer peripheral surfaces 21a and 5b in a balanced manner and the indicated value of the gauge 41 becomes constant, the coaxial adjustment (centering) of the holder body 17 is completed (step 403, FIG. 6). (B)).

  Then, the three knurled bolts 31 that have been temporarily fastened are evenly tightened, the jigs 16 and 30 and the gauge 41 are removed, and the holder body 17 is completely fixed on the table 5 (step 404).

  When the attachment of the holder body 17 to the table 5 is completed, the workpiece 3 is held by the work holder 6.

  As shown in FIGS. 7 and 9, the workpiece 3 previously stored in the work cover 7 is stored together with the work cover 7 in the holder body 17 (step 405, FIG. 7A).

Next, the attachment portion 37 of the shaft 12 is attached to the tool shaft 8 in the raised position, and the spacer 36 is placed on the object 3 and the holder cover 18 is placed on the holder body 17 (FIG. 7B). ), The tool shaft 8 is lowered, and the shaft 12 is inserted into the inner hole of the object to be polished 3 (FIG. 7C). As a result, the tapered portion 25 engages with the concave portion 26, the small-diameter shaft portion 39 is fitted into the circular hole 27, and the shaft 12 is supported from above and below by the tool shaft 8 and the through portion 24 and is upright with respect to the bottom wall portion 19. It is installed in a state, and the axis of the shaft 12 coincides with the rotation axis O ₁ . As the shaft 12 is inserted, a part of the inner peripheral end surface 2a of the glass substrate 2 constituting the object to be polished 3 that is not in a predetermined position is pressed against the outer peripheral surface of the tapered portion 25 or the large-diameter shaft portion 38. Thereby, the glass substrate 2 is positioned so that the axis of the inner hole coincides with the rotation axis O ₁ .

  Subsequently, the holder cover 18 is attached to the holder main body 17, and the object to be polished 3 on which each glass substrate 2 is positioned is fixed by sandwiching the object to be polished 3 between the bottom wall part 19 and the pressing part 22 (step 406). FIG. 7 (D)).

  After this positioning and fixing, the tool shaft 8 is raised, the shaft 12 is pulled upward, and is removed from the inner hole of the object to be polished 3 (step 407, FIG. 7E). Since the object to be polished 3 is fixed in the previous step, it is prevented that the positioned state accompanies the removal of the shaft 12.

  The shaft 12 is removed from the tool shaft 8 after being pulled out. Instead, the polishing brush 10 is attached to the tool shaft 8, and the polishing brush 10 is inserted into the inner hole of the object to be polished 3 (step 408).

  Then, either the table 5 and the tool shaft 8 are rotated at different angular velocities, or one of them is rotated, and both are rotated relatively, whereby the polishing brush 10 is polished via the polishing liquid supplied from the nozzle 11. The inner peripheral end face 3a is slidably contacted with the inner peripheral end face 3a of the body 3, and the inner peripheral end face 3a is polished (step 409). Note that the polishing brush 10 may be repeatedly moved up and down by the lifting device during polishing.

  In this embodiment, the bottom wall part 19 of the holder main body 17 of the work holder 6 is attached on the table 5, a plurality of glass substrates 2 are laminated on the bottom wall part 19, and the inner holes ( The glass substrate 2 is positioned on the lower holding portion by installing the shaft 12 in an upright state with respect to the bottom wall portion 19 so as to pass through the inner hole) of the object 3 to be polished, and the positioned glass substrate 2 is positioned. Since the shaft 12 is removed from the inner hole of the object to be polished 3 and is polished by inserting the polishing brush 10 into the inner hole, the glass substrate 2 is polished. Positioning and fixing are performed immediately before polishing, and the tolerance and roundness of the inner hole can be improved. That is, the shaft 12 is pulled out between the positioning / fixing stage and the polishing stage of the glass substrate 2, and this pulling process is performed by measuring the overlap between the positioned and fixed glass substrates 2 (inner holes). The position of the glass substrate 2 with respect to the table 5 is not disturbed by shifting in the direction. In addition, when the work holder is fixed on the table after the laminated glass substrate is accommodated in the work holder, the accuracy of mounting the work holder on the table decreases due to, for example, abrasive grains entering between the work holder and the table. However, there is a concern that the positioning accuracy of the glass substrate with respect to the table may be lowered. However, in the above configuration, the holder body 17 of the work holder 6 is attached to the table 5 in advance (before holding the glass substrate 2). Therefore, even if there is some problem in the mounting accuracy of the work holder 6 with respect to the table 5, the error can be absorbed in the subsequent positioning process of the glass substrate 2.

  Here, in particular, when a plurality of glass substrates 2 are stacked on the bottom wall portion 19, the glass substrate 2 is accommodated in a state where a plurality of glass substrates 2 are stacked on a bottomed cylindrical work cover 7 opened upward. Since the glass substrate 2 housed in is installed on the bottom wall portion 19 together with the work cover 7, the glass substrate 2 can be easily set to the work holder 6 in which the holder body 17 is fixed to the table 5.

  Incidentally, the polishing apparatus 1 may have a shaft that can be expanded and contracted in the radial direction. For example, the shaft 47 shown in FIG. 10 has an attachment portion 48 attached to the tool shaft 8, a rod-like portion 49 having a conical surface 49 a that is coaxial with the attachment portion and decreases in diameter downward, and the rod-like portion 49. It is relatively slidable in the vertical direction and is movable in the radial direction, and has a total of three interlocking portions 50 provided on the outer periphery of the rod-like portion 49. The interlocking portion 50 has an outer surface 50a that forms a cylindrical surface, an inner surface 50b that abuts against the conical surface 49a of the rod-like portion 49, and is biased radially inward by an elastic member (not shown). Yes. When the rod-like portion 49 slides relatively downward with respect to the interlocking portion 50, the conical surface 49 of the rod-like portion 49 widens the space between the inner surfaces 50b of each interlocking portion 50, and each interlocking portion 50 moves radially outward. And the diameter of the shaft 47 prescribed | regulated by the outer surface 50a of the interlocking | linkage part 50 increases. On the other hand, when the rod-like portion 49 slides relatively upward with respect to the interlocking portion 50, the interval between the inner surfaces 50b of the interlocking portions 50 is narrowed by the urging force of the elastic member, and the interlocking portions 50 move inward in the radial direction. As a result, the diameter of the shaft 47 decreases.

  In order to position the glass substrate 2 using the shaft 47, first, as shown in FIG. 11, the work holder 7 in which the object to be polished 3 is accommodated is placed in the holder main body 17 attached on the table 5. (FIG. 11 (A)), the contracted shaft 47 is attached to the tool shaft 8 (FIG. 11 (B)), and the shaft 47 is lowered and inserted into the inner hole of the object 3 (FIG. 11). (C)). Then, the shaft 47 is expanded in the radial direction by relative sliding between the rod-shaped portion 49 and the interlocking portion 50, and a pressing force is applied to the entire inner peripheral end surface 2 a of each glass substrate 2 by the outer surfaces 50 a of the three interlocking portions 50. Each glass substrate 2 is positioned at a predetermined position (FIG. 11D), and after this positioning state is fixed by the holder cover 18 (FIG. 11E), the shaft 47 is contracted in the radial direction to be polished. It is pulled upward from the inner hole of the body 3 (FIG. 11 (F)). As described above, when the shaft 47 is inserted / removed, the shaft 47 is contracted in the radial direction, and when the glass substrate 2 is positioned, the shaft 47 is expanded in the radial direction. Therefore, it is possible to prevent an excessive force from being applied to the glass substrate 2, and at the time of positioning the glass substrate 2, positioning can be performed with high accuracy by expanding the diameter of the shaft 47.

  In the above description, after the holder main body 17 is set in the polishing apparatus, the shaft 12 is set, and the work holder 7 on which the laminated body in which the substrates are laminated in advance is placed. ing. However, the present invention is not limited to the above. For example, the glass substrate 2 may be set on the holder body 17 without using the work holder 7.

  Besides, the holder cover 18 has a screw mechanism (male screw, female screw) at a portion where the holder cover 18 itself and the holder body 17 are in contact with each other, and by rotating the holder cover 18, It is good also as a structure which fixes the laminated body of the glass substrate 2. FIG.

  Furthermore, a part of the holder main body 17 is lost (the peripheral wall portion 20 is eliminated and only the bottom wall portion 19 is used), and the holder cover 18 and a part of the holder main body 17 (the peripheral wall portion 20) are integrated. May be adopted. Specifically, the holder cover has a cylindrical shape, and when the glass substrate 2 is set, the holder cover and the bottom wall portion 19 may be fixed. In this case, since there is no peripheral wall part 20 when setting a glass substrate, the holder cover 18 can be lost and the laminated body of a glass substrate can be set easily.

[Example]
Examples of a glass substrate for a magnetic disk and a method for manufacturing the magnetic disk to which the present invention is applied will be described below. This embodiment is valid for any size of disk of 0.8 inch type, 1.0 inch type, 1.8 inch type, 2.5 inch type or 3.5 inch type.

(1) Shape processing step and first lapping step (step 1: see FIG. 8)
First, the melted aluminosilicate glass was molded into a disk shape by direct pressing using an upper mold, a lower mold, and a body mold to obtain an amorphous plate glass. In addition to direct pressing, a disk-shaped glass substrate for a magnetic disk may be obtained by cutting a sheet glass formed by a downdraw method or a float method with a grinding wheel.

  Next, both main surfaces of the plate glass were lapped to form a disk-shaped glass base material. The lapping process was performed using alumina free abrasive grains by a double-sided lapping 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 lapping. went. By this lapping process, a glass base material having a flat main surface was obtained.

(2) Cutting process (Step 2)
The glass base material obtained in the previous step was cut using a diamond cutter to cut out a disk-shaped glass substrate. Next, the inner hole was formed in the center part of the glass substrate using the cylindrical diamond drill, and it was set as the annular | circular shaped glass substrate (coring). Then, the outer peripheral end face and the inner peripheral end face were ground with a diamond grindstone and subjected to predetermined chamfering (forming, chamfering).

(3) Second wrapping step (Step 3)
A second lapping process for lapping was performed on both the front and back main surfaces of the glass substrate obtained in the previous process in the same manner as in the first lapping process. By performing the second lapping step, it is possible to remove fine irregularities formed on the main surface by cutting and end face polishing in the previous step, and to complete the main surface polishing step described later in a short time. become.

(4) End face polishing process (Step 4)
Subsequently, the outer peripheral end face of the glass substrate was mirror polished by a brush polishing method. At this time, as the abrasive grains, a slurry (free abrasive grains) containing cerium oxide abrasive grains was used.

  The inner peripheral end surface was mirror polished by the polishing apparatus 1. Since this has already been described, a description thereof will be omitted (see FIGS. 6, 7 and 9).

  The glass substrate that had finished the polishing of the end faces on the outer periphery and inner periphery was washed with water. By this polishing, the end surface of the glass substrate was processed into a mirror surface state capable of preventing the precipitation of sodium and potassium. In particular, the inner peripheral end face was able to improve the dimensional tolerance and roundness of the inner hole even when a large number of 200 to 300 glass substrates were laminated and polished.

(5) Main surface polishing step (Step 5)
As the main surface polishing step, first, the first polishing step was performed. This first polishing step is mainly intended to remove scratches and distortions remaining on the main surface in the lapping step described above. In the first polishing step, the main surface was polished using a hard resin polisher by a double-side polishing apparatus having a planetary gear mechanism, and cerium oxide abrasive grains were used as the polishing liquid.

  The glass substrate after the first polishing step was washed by being sequentially immersed in each washing tank of neutral detergent, pure water, and IPA (isopropyl alcohol).

  Next, the 2nd grinding | polishing process aiming at finishing a main surface in a mirror surface shape was performed. In the second polishing step, mirror polishing of the main surface was performed using a soft foam resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the polishing liquid, cerium oxide abrasive grains finer than the cerium oxide abrasive grains used in the first polishing step were used.

  The glass substrate which finished the 2nd grinding | polishing process was immersed in each washing tank of neutral detergent, a pure water, and IPA one by one, and ultrasonically cleaned.

(6) Chemical strengthening process (Step 6)
The glass substrate obtained in the previous process was chemically strengthened. Chemical strengthening is performed by preparing a chemical strengthening solution in which potassium nitrate and sodium nitrate are mixed and heating it, preheating the cleaned glass substrate, and immersing the glass substrate in the chemical strengthening solution. It was. The immersion in the chemical strengthening solution was performed by storing a plurality of glass substrates in a holder that holds the end surfaces so that the entire surface of the glass substrate is chemically strengthened.

  By immersing in the chemical strengthening solution, lithium ions and sodium ions on the surface layer of the glass substrate are replaced with sodium ions and potassium ions in the chemical strengthening solution, respectively, and the glass substrate is strengthened.

  The glass substrate after the chemical strengthening treatment was immersed in a water bath and rapidly cooled, then immersed in concentrated sulfuric acid for cleaning, and further immersed in each cleaning bath of pure water and IPA for ultrasonic cleaning.

  Through the steps so far, a flat and smooth high-rigidity glass substrate for a magnetic disk was obtained.

(7) Magnetic disk manufacturing process (Step 7)
On both main surfaces of the glass substrate obtained through the steps up to (6), an adhesion layer made of Cr alloy, a soft magnetic layer made of FeCoCrB base alloy, an underlayer made of Ru, and a perpendicular magnetic recording layer made of CoCrTi base alloy A perpendicular magnetic recording disk was manufactured by sequentially forming a protective layer made of hydrogenated carbon and a lubricating layer made of perfluoropolyether. Although a perpendicular magnetic recording type disk is manufactured here, a magnetic layer or the like may be formed as an in-plane magnetic recording type.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above embodiment, the shaft 47 has been described as a shaft that can be expanded and contracted. However, the expansion and contraction method is not limited to this, and the shaft 47 is coaxial with the mounting portion 48 in the forward and reverse directions as shown in FIG. You may have the rod-shaped part 49 which can rotate, and the interlocking | linkage part 50 which can be moved to a radial direction and was provided in the outer periphery of the rod-shaped part 49 a total of three. The rod-shaped portion 49 is composed of three cam surfaces (surfaces having a curved surface in which the traversing trajectory of the surface gradually moves away (approaches) with respect to the axis of the rod-shaped portion 49). The outer peripheral surface 50a forms a cylindrical surface with a fan shape, and the top portion 50b contacts the cam surface 49a by the biasing force of an elastic member (not shown). When the rod-like portion 49 rotates in the arrow A direction, the shaft 47 expands in the radial direction, and when the rod-like portion 49 rotates in the arrow B direction, the shaft 47 contracts in the radial direction.

  The present invention can be used for manufacturing a glass substrate for a magnetic disk, particularly for polishing an inner peripheral end face.

It is sectional drawing which shows the grinding | polishing apparatus of the glass substrate for magnetic discs. It is a top view which shows a table. It is a top view which shows the holder main body of a work holder. It is sectional drawing which shows a work cover. It is a side view which shows a shaft. The attachment procedure on the table of a holder main body is shown, (A) is explanatory drawing which shows the inclination adjustment of a holder main body, (B) is explanatory drawing which shows the coaxial adjustment of a holder main body. The procedure for holding the laminated glass substrate on the work holder is shown. (A) is an explanatory view showing the state in which the object to be polished accommodated in the work cover is accommodated in the holder main body. (B) is the shaft attached to the tool shaft. (C) is an explanatory view showing a state in which the shaft is inserted into the inner hole of the object to be polished, (D) is an explanatory view showing a state in which the holder cover is attached to the holder body, (E) It is explanatory drawing which shows a mode that the shaft was extracted from the inner hole of the to-be-polished body. It is a flowchart which shows the manufacturing method of a magnetic disc. It is a flowchart which shows the grinding | polishing method by a grinding | polishing apparatus. The shaft which can be expanded-contracted is shown, (A) is the side view, (B) is a longitudinal cross-sectional view. The procedure for holding a glass substrate laminated using a shaft that can be expanded and contracted by a work holder is shown, (A) is an explanatory view showing a state in which an object to be polished housed in a work cover is housed in a holder body, (B) Is an explanatory view showing a state where a reduced diameter shaft is attached to the tool shaft, (C) is an explanatory view showing a state where the reduced diameter shaft is inserted into the inner hole of the object to be polished, and (D) is an enlarged view of the shaft. (E) is an explanatory view showing a state in which the holder cover is attached to the holder main body, (E) is a diameter reduction of the shaft, and (E) is an explanatory view showing the state of positioning the glass substrate constituting the polished body. It is explanatory drawing which shows a mode that it pulled out from the inner hole. It is explanatory drawing which shows the other example of the shaft which can be expanded / contracted.

Explanation of symbols

1 ... Polishing device (manufacturing device)
2 ... glass substrate 2a ... inner peripheral end face 3 (of glass substrate) ... object 3a to be polished ... inner peripheral end face 5 (of object to be polished) ... table 6 ... work holder 7 ... work cover 10 ... polishing brush (polishing object)
12 ... Shaft 19 ... Bottom wall (lower holding part)
22 ... holding part (upper holding part)
24 ... penetrating part 25 ... taper part 26 ... concave part 35 ... insertion hole 47 ... (expandable / shrinkable) shaft

Claims (9)

In the method for producing a glass substrate for a magnetic disk, comprising a step of polishing an inner peripheral end face by laminating a glass substrate having an inner hole and inserting a polishing body into the communicating inner hole to polish
At the position where the polishing body of the polishing apparatus is attached, instead of the polishing body, a step of attaching a positioning member so that its central axis coincides with the central axis of the polishing body;
A step of laminating a plurality of glass substrates;
Passing the positioning member through the communicating inner hole of the laminated glass substrate;
Fixing the laminated glass substrate;
Removing the positioning member from the communicating inner hole of the positioned glass substrate;
Attaching the polishing body to the polishing apparatus instead of the positioning member;
A method of manufacturing a glass substrate for a magnetic disk, comprising: inserting the polishing body into an inner hole communicating with the positioned glass substrate. The lower holding portion of the work holder that is sandwiched between the upper holding portion and the lower holding portion in a state where a plurality of the glass substrates are stacked on a table of a polishing apparatus that polishes the inner peripheral end surface of the inner hole formed in the glass substrate. Attaching the process,
A step of laminating a plurality of the glass substrates on the lower holding portion;
A step of installing the shaft in an upright state with respect to the lower holding portion so as to penetrate through the inner hole communicated with the glass substrate laminated on the lower holding portion;
Positioning the laminated glass substrate by the shaft;
Pressing the glass substrate positioned on the lower holding portion from above with the upper holding portion;
Removing the shaft from the communicating inner hole of the positioned glass substrate;
Inserting a polishing body into the communicating inner hole of the positioned glass substrate;
And a step of polishing the inner peripheral end surface with the polishing body by relatively rotating or moving the table and the polishing body. The shaft is expandable / contractable in the radial direction,
In the step of positioning the laminated glass substrate by the shaft, the shaft is expanded in the radial direction for positioning,
5. The magnetic disk glass substrate according to claim 4, wherein in the step of removing the shaft from the communicating inner hole of the positioned glass substrate, the shaft is contracted in the radial direction and removed. Production method. The step of laminating a plurality of the glass substrates on the lower holding part,
A step of accommodating a plurality of the glass substrates stacked in a bottomed cylindrical work cover opened upward;
4. The method of manufacturing a glass substrate for a magnetic disk according to claim 2, further comprising a step of placing the glass substrate accommodated in the work cover together with the work cover on the lower holding portion. 5. . A work holder sandwiched between the upper holding portion and the lower holding portion in a state in which a plurality of glass substrates having inner holes formed thereon are laminated,
A table to which the lower holding portion is attached;
A shaft that can expand and contract in the radial direction;
A polishing body mounting portion to which a polishing body for polishing the inner peripheral end surface of the inner hole by relative rotation or movement with the table is mounted;
The shaft is positioned on the table so as to position the glass substrate by extending radially through the inner hole when a plurality of the glass substrates are stacked on a lower holding portion attached to the table. On the other hand, it can be installed in an upright state, and can be removed from the inner hole by contracting in a radial direction with the upper glass holding portion held from above.
The polishing body attached to the polishing body attaching portion is inserted into the inner hole after the shaft is removed from the inner hole of the positioned glass substrate, and the inner peripheral end face is polished. Equipment for manufacturing glass substrates for disks. It has a bottomed cylindrical shape that opens upward, and includes a work cover that accommodates the glass substrate in a stacked state,
6. The apparatus for manufacturing a glass substrate for a magnetic disk according to claim 5, wherein the glass substrate accommodated in the work cover is installed on the lower holding portion together with the work cover. The lower holding portion of the work holder that is sandwiched between the upper holding portion and the lower holding portion in a state where a plurality of the glass substrates are stacked on a table of a polishing apparatus that polishes the inner peripheral end surface of the inner hole formed in the glass substrate. Attaching the process,
A step of laminating a plurality of the glass substrates on the lower holding portion;
A step of installing the shaft in an upright state with respect to the lower holding portion so as to penetrate through the inner hole communicated with the glass substrate laminated on the lower holding portion;
Positioning the laminated glass substrate by the shaft;
Pressing the glass substrate positioned on the lower holding portion from above with the upper holding portion;
Removing the shaft from the communicating inner hole of the positioned glass substrate;
Inserting a polishing body into the communicating inner hole of the positioned glass substrate;
Polishing the inner peripheral end surface with the polishing body by relatively rotating or moving the table and the polishing body;
And a step of forming a magnetic layer on a surface of the glass substrate after the glass substrate is polished. The shaft is expandable / contractable in the radial direction,
In the step of positioning the laminated glass substrate by the shaft, the shaft is expanded in the radial direction for positioning,
8. The method of manufacturing a magnetic disk according to claim 7, wherein, in the step of removing the shaft from the communicating inner hole of the positioned glass substrate, the shaft is contracted in the radial direction and removed. The step of laminating a plurality of the glass substrates on the lower holding part,
A step of accommodating a plurality of the glass substrates stacked in a bottomed cylindrical work cover opened upward;
The method for manufacturing a magnetic disk according to claim 7, further comprising a step of placing the glass substrate accommodated in the work cover together with the work cover on the lower holding portion.

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