JP2008059727A - Tool for work holder, work holder and manufacturing method of glass substrate for magnetic disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the number of lamination when the inner peripheral parts thereof are polished while tolerance and roundness of inner holes of the glass substrates are enhanced. <P>SOLUTION: End surfaces of a plurality of laminated glass substrates 10 interposed between an upper plate 104 and a lower plate 101 and fixed to a work holder 100 are polished and the upper plate 104 and the lower plate 101 are connected by using a connection part 102 while at least one of the upper plate 104 and the lower plate 101 of the work holder 100 is pressed to the other side so that the upper plate 104 and the lower plate 101 positioned at both ends of the plurality of glass substrates 10 are kept parallel to each other by using a tool 300 for work holder for connecting the work holder 100 fixing positions of the plurality of laminated glass substrates 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to polishing of an inner peripheral end face of a magnetic disk glass substrate. In addition, the up-down direction referred to in the present application is the up-down direction in a normal use mode, and is not necessarily the up-down direction with respect to the gravity direction.

  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 from is narrowed to about 8 nm. For this reason, if there is an uneven shape on the magnetic disk surface, there may be a crash failure in which the magnetic head collides, or a thermal asperity failure that causes a read error due to adiabatic compression or contact of air. 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 (Japanese Patent Laid-Open No. 10-154321), it is possible to prevent generation and adsorption of particles on the substrate end surface by polishing the outer periphery and inner peripheral end surface of the substrate until they reach the mirror surface, thereby solving the above problem. Yes.

As a configuration for polishing the inner peripheral end face of the glass substrate, a polishing method using a rotating brush as described in Patent Document 2 (Japanese Patent Laid-Open No. 11-221742) is known. In this conventional polishing method, a disk-shaped glass substrate 1 is laminated into a cylindrical shape, and a rotating brush 50 is inserted into a communicating inner hole, and the glass substrate 1 and the rotating brush 50 are rotated while supplying a polishing liquid. By doing so, the inner peripheral end face is polished.
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 read / write speed of the hard disk, 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 small hard disks to be mounted especially on mobile phones, digital cameras, portable music players, etc., and magnetic disks are required to be further downsized, higher in recording density, and lower in cost. It has been.

  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 stacked and polished up to now, if 300 sheets are stacked and polished, production can be simply performed with 1/3 tact (processing time). However, as the number of stacked layers is increased, the tolerance and roundness of the inner holes tend to decrease.

  Accordingly, the present invention provides a work holder jig, a work holder, and a magnetic disk glass capable of increasing the number of laminated layers at the time of inner circumferential polishing while improving the tolerance and roundness of the inner hole of the glass substrate. It aims at providing the manufacturing method of a board | substrate.

  As a result of intensive studies on the above problems, the inventors of the present invention have found that the tolerance and roundness of the inner hole are reduced when a plurality of laminated glass substrates are tilted during inner circumference polishing. I found out. And as a result of examining the polishing process to solve this problem, when the number of glass substrates increases in the stage of stacking and holding the glass substrates on the work holder, the central axis of the glass substrate and the rotation axis of the work holder I found out the fact that the degree of coincidence is likely to decrease. When the upper support portion of the work holder is fastened and fixed, the degree of coincidence between the central axis of the glass substrate and the rotation axis of the work holder can be improved by holding the glass substrate in an upright state. As a result, the present invention has been completed.

  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 sandwich a plurality of laminated glass substrates between an upper plate and a lower plate, Both ends of the plurality of glass substrates using a work holder jig for connecting a work holder for fixing the positions of the plurality of laminated glass substrates by connecting the lower plate with a connecting portion So that the upper plate and the lower plate are maintained parallel to each other, at least one of the upper plate and the lower plate of the work holder is pressed to the other side, and the upper plate and the lower plate are connected to each other. And the end face of the glass substrate sandwiched between the upper plate and the lower plate and fixed to the work holder is polished.

  A representative configuration of the work holder jig according to the present invention includes a lower support portion, an upper frame connected to the lower support portion, and an upper support portion fastened and fixed to the upper frame, A jig for holding a glass substrate on a work holder that holds a plurality of glass substrates stacked between a lower support portion and an upper support portion, and is placed in a state where the work holder stands upright. And a pressing portion that presses the upper support portion of the work holder toward the lower support portion so that the upper support portion and the lower support portion are maintained parallel to each other. Features. Here, the fact that the work holder stands upright means that the rotation axis of the work holder and the mounting surface of the gantry are perpendicular to each other.

  According to the above configuration, when the upper support portion is fastened and fixed in the work holder, the laminated glass substrates can be held in an upright state, and the degree of coincidence between the central axis of the glass substrate and the rotation axis of the work holder Can be improved.

  The pressing part can be constituted by an air cylinder. The mechanism can be configured in a simple manner, and an excessive pressing force can be prevented from damaging the glass substrate.

  In order to solve the above problems, a typical configuration of the work holder according to the present invention includes a lower support part, an upper frame connected to the lower support part, and an upper side fastened and fixed to the upper frame. Fitting that fits with the center shaft in a work holder that holds a glass substrate laminated between a lower support portion and an upper support portion by inserting a center shaft into a central inner hole and holding the glass substrate between the lower support portion and the upper support portion. A positioning member having a hole is provided, the positioning member is provided with a pin or boss hole extending in the axial direction of the center shaft, and the upper support portion is provided with a boss hole or pin extending in the axial direction of the center shaft. Alternatively, the boss hole can be inserted into and removed from the boss hole or pin of the upper support portion.

  According to the above configuration, it is possible to ensure the positional accuracy between the upper support portion and the center shaft at the upper part of the work holder, and it is easy to pull out the center shaft. It is possible to prevent the support portion from being polished.

  ADVANTAGE OF THE INVENTION According to this invention, the number of lamination | stacking in the case of inner periphery grinding | polishing can be increased, improving the tolerance and roundness of the inner hole of a glass substrate. Moreover, workability | operativity improves and it can aim at shortening of the working time required in order to make a work holder hold | maintain a glass substrate. Further, the glass substrate can be prevented from being damaged when the center shaft is pulled out, and the productivity can be improved. For these reasons, it is possible to improve the quality of the glass substrate and reduce the production cost.

  Embodiments of a method for manufacturing a work holder jig, a work holder, and a magnetic disk glass substrate according to the present invention will be described. FIG. 1 is a diagram illustrating an inner peripheral end surface polishing apparatus, FIGS. 2 and 3 are diagrams illustrating a work holder, FIG. 4 is a diagram illustrating a work holder jig, and FIG. 5 is a diagram using a work holder jig. FIG. 6 is a flowchart for explaining a process for holding the glass substrate. FIG. 6 is a flowchart for explaining the work for holding the glass substrate on the work holder. Portions overlapping with those in the conventional example are given the same reference numerals and description thereof is omitted. Note that specific dimensions, shapes, materials, and other numerical values shown in the following embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. .

  A polishing apparatus 1 shown in FIG. 1 is an apparatus for polishing inner peripheral end surfaces of a plurality of glass substrates. The work holder 100 that holds the plurality of glass substrates 10 in a stacked state is fixed to the table 201 by fixing means such as a bolt 208. A plurality of glass substrates 10 (for example, 100 to 300) are laminated and sandwiched between the lower support portion 101 and the upper support portion 104. The table 201 is configured to be rotatable with respect to the base 202. The table 201 can be placed with the work holder 100 standing upright, and the work holder 100 is fixed in a state in which the rotation axis (that is, the central axis of the glass substrate) and the rotation axis of the table 201 are aligned. . “Upright” means that the rotation axis of the work holder 100 and the mounting surface of the base 202 are perpendicular to each other.

  A brush 203 is inserted into the inner hole of the glass substrate 10 held by the work holder 100. The brush shaft 204 of the brush 203 is rotationally driven by a drive shaft 205 at its upper end and is rotatably supported by a brush lower end support portion 206 at its lower end. The brush 203 is also swung in the vertical direction while being driven to rotate, thereby polishing the inner peripheral end surface of the glass substrate 10. At the time of polishing, a slurry mixed with abrasive grains is supplied from the nozzle 207.

  Next, the steps of holding the glass substrate on the work holder 100 will be described while explaining the configurations of the work holder 100 and the work holder jig, using the flowcharts of FIGS. 2 to 5 and FIG. 6.

  The center shaft 110 shown in FIG. 2A includes a main shaft portion 110a having a diameter substantially equal to the inner hole of the glass substrate 10, and a base portion 110b having a diameter larger than that of the main shaft portion 110a. Then, the lower spacer 111 is inserted so as to be put on the base portion 110b, and the inner holes of the plurality of glass substrates 10 are inserted and laminated thereon (S101). Between the glass substrates 10, a spacer 113 made of a nonwoven fabric or the like is interposed to prevent scratches. When a predetermined number of glass substrates 10 are stacked, the upper spacer 112 is placed at the end (uppermost portion). The lower spacer 111 and the upper spacer 112 can be made of a resin such as polyacetal, for example.

  2B includes a lower support portion 101, an upper frame 103 connected to the lower support portion 101 by a support column 102, and an upper support portion 104 fastened and fixed to the upper frame 103. It has. That is, the lower support portion 101 to the upper frame are fixedly configured, but the upper support portion 104 is a member that is fastened after the glass substrate 10 is stored therein.

  The lower support portion 101 is formed such that the lower surface 101a (the surface that contacts the table 201 of the polishing apparatus 1) and the center axis of the work holder 100 are perpendicular to each other. In addition, a hole 101 b that fits with the base portion 110 b of the center shaft 110 is formed at the center of the lower support portion 101. The central axis of the hole 101 b is the same axis as the central axis of the work holder 100.

  The support column 102 is fixed perpendicularly to the lower surface 101 a of the lower support portion 101. In other words, the support 102 and the center axis of the work holder are parallel.

  As shown in FIG. 2C, the upper frame 103 is formed with a hole 103a having a size capable of inserting a glass substrate at the center. Further, a knurled bolt 105 for fastening the upper support portion 104 and a boss hole 103b for inserting the pin 106b of the positioning member 106 are provided.

  As shown in FIG. 2D, the upper support portion 104 is formed with a hole 104a having a size capable of inserting the brush 203 in the center portion. The size of the hole 104a may be larger than the diameter of the inner hole of the glass substrate 10 and smaller than the diameter of the outer periphery. Further, the upper support portion 104 is provided with a deformation hole 104 b for fastening with a knurled bolt 105. The deformation hole has a large-diameter portion into which the head of the knurled bolt 105 can be inserted, and a small-diameter long hole portion that can be fastened. The upper support portion 104 can be attached without removing the knurled bolt 105 from the upper frame 103. It is possible. The upper support portion 104 includes a boss hole 104c for inserting the pin 106b of the positioning member 106.

  The positioning member 106 positions the upper end of the center shaft 110 when the upper support portion 104 is fastened and fixed. As shown in FIG. 2 (e), a fitting hole 106a for fitting with the center shaft is provided at the center of the positioning member 106 so that the pin 106b that can be inserted into and removed from the boss holes 103b and 104c protrudes downward. Provided. Further, on the upper surface of the positioning member 106, a step portion 106c for abutting a pusher of a work holder jig to be described later is provided. When the pin 106b of the positioning member 106 is inserted into the boss holes 103b and 104c, the center axis of the center shaft 110 held in the fitting hole 106a is the same axis as the center axis of the work holder 100.

  Next, as shown in FIG. 3A, the laminated glass substrate 10 is placed on the lower support portion 101 with the center shaft 110 standing upright (S102). That is, the laminated glass substrate 10 is inserted into the work holder 100, and the base portion 110 b of the center shaft 110 is fitted into the hole 101 b of the lower support portion 101. And the upper side support part 104 is mounted on the glass substrate 10 (S103). At this time, the knurled bolt 105 is combined with the elongated hole portion of the deformation hole 104b, but is not yet tightened and is in a loose state. The positioning member 106 is inserted into the boss holes 103b and 104c while the center shaft 110 is fitted into the fitting hole 106a.

  In this way, the work holder 100 is in a state in which a series of members are stacked as shown in FIG. In this state, the glass substrate 10 is fixed by tightening the knurled bolt 105. At this time, a work holder jig 300 shown in FIG. 4 is used.

  A work holder jig 300 shown in FIG. 4 includes a gantry 302 on which a work holder 100 can be placed in an upright state at a lower portion of a frame body 301, and an upper support portion 104 of the work holder 100 is mounted on an upper portion of the frame body 301. A pressing portion 303 that presses toward the lower support portion 101 is provided. Here, “upright” means that the central axis of the work holder 100 is perpendicular to the mounting surface (upper surface) of the gantry 302.

  The pressing part 303 is an air cylinder, and the pusher 304 can be advanced and retracted with respect to the work holder 100. The pusher 304 is configured to press the upper support portion 104 via the positioning member 106, and comes into contact with the stepped portion 106 c of the positioning member 106. Note that the pressing direction by the pressing portion 303 (the moving direction of the pusher 304) coincides with the central axis of the work holder 100 placed.

  Then, the work holder 100 is placed on the mount 302 as shown in FIG. 4 (S104), and the positioning member 106 (that is, the upper support portion 104) is supported on the lower side by the pressing portion 303 as shown in FIG. Press toward the part 101 (S105). Both the lower surface of the pusher 304 and the upper surface of the stepped portion 106 c in contact with the pusher 304 are perpendicular to the central axis of the work holder 100. Therefore, when the pusher 304 presses the positioning member 106, the glass substrate is pressed evenly in all directions. Since the spacer 113 sandwiched between the glass substrates 10 is slightly elastic, the stacked glass substrates 10 are compressed in height. In this state, the operator knurled bolt 105 is turned to fasten and fix the upper support portion 104 to the upper frame 103 (S106).

  And as shown in FIG.5 (b), after canceling the press by the press part 303 (S107), the positioning member 106 is removed from the work holder 100, and the center shaft 110 is extracted from the downward direction (S108). When the pressing is released, the laminated glass substrate 10 expands as a whole by the elastic recovery force of the spacer 113, and is thus firmly held between the lower support portion 101 and the upper support portion 104. Then, the work holder 100 is attached to the polishing apparatus 1 described with reference to FIG. 1, and the inner peripheral end face of the laminated glass substrate 10 is polished (S109).

  That is, according to the above configuration, the plurality of laminated glass substrates 10 are sandwiched between the upper plate (upper support portion 104) and the lower plate (lower support portion 101), and the upper plate and the lower plate are connected to the connection portion (the support column). 102), by using the work holder jig 300 for connecting the work holders 100 for fixing the positions of the plurality of laminated glass substrates 10 at the both ends of the plurality of glass substrates 10. At least one of the upper plate and the lower plate of the work holder 100 is pressed to the other side so that the upper plate and the lower plate are kept parallel to each other, and the upper plate and the lower plate are connected to each other (knurl bolt). 105), and the end face of the glass substrate that is sandwiched between the upper plate and the lower plate and fixed to the work holder 100 is polished.

  Here, if the work holder jig 300 is not used, the operator fixes the glass substrate 10 by manually tightening the knurled bolt 105. However, since the knurled bolts 105 are provided in this embodiment in three places (actually, there are also four places), it is difficult to tighten them evenly. If the tightening force is uneven, the glass substrate laminated on the tightly tightened side is inclined, and the upper support portion 104 on the loosely tightened side is in a floating state. If the glass substrate is tilted in this way, the dimensional tolerances of each part are set to be extremely small, so that it becomes extremely difficult to pull out the center shaft 110, and if it is pulled out forcibly, damage such as cracks and chips will occur. Will be given. Therefore, it is conceivable that the center shaft 110 is first pulled out while the knurled bolt 105 is loosely tightened, and the knurled bolt 105 is further tightened to hold the glass substrate. However, the glass substrate 10 tends to be tilted and polished. When applied to the device 1, the tolerance and roundness of the inner hole are reduced.

  On the other hand, by using the work holder jig 300 as in the present embodiment, when the upper support 104 is fastened and fixed in the work holder 100, the stacked glass substrates 10 can be held in an upright state. The degree of coincidence between the central axis of the glass substrate 10 and the rotation axis of the work holder 100 can be improved. For this reason, even after the knurled bolt 105 has been securely tightened, the center shaft 110 can be easily pulled out, and the center axis of the work holder 100 can coincide with the center axis of the glass substrate.

  This also works in the same way when the number of glass substrates is increased. Therefore, the center shaft 110 can be easily pulled out even when the number of glass substrates is increased, and the glass substrate can be kept upright. Accordingly, it is possible to increase the number of glass substrates that can be processed in one polishing step, improve working efficiency, and reduce production costs.

  Compared to the case of manual work, the work of holding the glass substrate with the work holder 100 on average takes 2-3 minutes in the manual work, but in the configuration of the present embodiment, it takes about 20 seconds, thus shortening the work time. Can be achieved. Further, since the glass substrate is not damaged when the center shaft 110 is pulled out, the production efficiency and quality can be improved.

[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 glass substrate for magnetic disk and magnetic disk are 0.8 inch type disk (inner diameter 6 mm, outer diameter 21.6 mm, plate thickness 0.381 mm), 1.0 inch type disk (inner diameter 7 mm, outer diameter 27.4 mm, It is manufactured as a magnetic disk having a predetermined shape such as a plate thickness of 0.381 mm) and a 1.8 inch type magnetic disk (inner diameter of 12 mm, outer diameter of 48 mm, plate thickness of 0.508 mm). Further, it may be manufactured as a 2.5 inch type disc or a 3.5 inch type disc.

(1) Shape processing step and first lapping step In the method of manufacturing a magnetic disk glass substrate according to this example, first, the surface of the plate glass is lapped (ground) to obtain a glass base material. Cut the material and cut out the glass disc. Various plate glasses can be used as the plate glass. This plate-like glass can be manufactured by using a known manufacturing method such as a press method, a float method, a downdraw method, a redraw method, or a fusion method using a molten glass as a material. Of these, plate glass can be produced at low cost by using the pressing method. As the material of the plate glass, amorphous glass or glass ceramics (crystallized glass) can be used. As the material for the plate glass, aluminosilicate glass, soda lime glass, borosilicate glass, or the like can be used. In particular, as an amorphous glass, an aluminosilicate glass can be preferably used in that it can be chemically strengthened and a magnetic disk substrate excellent in flatness of the main surface and substrate strength can be supplied.

In this example, 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. As the aluminosilicate _glass, SiO 2: 58 to 75 _{wt%, Al} 2 O 3: _{5~23 wt%,} Li 2 O: 3 to 10 _wt%, Na 2 O: 4 to 13 principal component weight% Chemically strengthened glass contained as

  Next, both main surfaces of the plate glass were lapped to form a disk-shaped glass base material. This lapping process was performed using alumina free abrasive grains with a double-sided lapping apparatus using a planetary gear mechanism. Specifically, the lapping platen is pressed on both sides of the plate glass from above and below, the grinding liquid containing free abrasive grains is supplied onto the main surface of the plate glass, and these are moved relative to each other for lapping. went. By this lapping process, a glass base material having a flat main surface was obtained.

(2) Cutting process (coring, forming, chamfering)
Next, the glass base material was cut using a diamond cutter, and a disk-shaped glass substrate was cut out from the glass base material. Next, using a cylindrical diamond drill, an inner hole was formed in the center of the glass substrate to obtain an annular glass substrate (coring). Then, the inner peripheral end face and the outer peripheral end face were ground with a diamond grindstone and subjected to predetermined chamfering (forming, chamfering).

(3) Second Lapping Step Next, a second lapping process was performed on both main surfaces of the obtained glass substrate in the same manner as in the first lapping step. By performing this second lapping step, it is possible to remove in advance the fine unevenness formed on the main surface in the cutting step and end surface polishing step, which are the previous steps, and shorten the subsequent polishing step on the main surface. Will be able to be completed in time.

(4) End surface grinding | polishing process Next, mirror polishing was performed with the brush grinding | polishing method about the outer peripheral end surface of the glass substrate. At this time, as the abrasive grains, a slurry (free abrasive grains) containing cerium oxide abrasive grains was used.

  The inner peripheral end face was polished by using the polishing apparatus 1 shown in FIG. 1 while holding the glass substrate 10 on the work holder 100 as described above. The process at this time will be described based on the flowchart shown in FIG.

  That is, first, as shown in FIG. 2A, the center shaft 110 is laminated while inserting the inner hole of the glass substrate 10 (S101). As shown in FIG. 3A, the laminated glass substrate 10 is placed on the lower support portion 101 with the center shaft 110 standing upright (S102). As shown in FIG.3 (b), the upper side support part 104 is mounted on the glass substrate 10 (S103). As shown in FIG. 4, the work holder 100 is placed on the mount 302 (S <b> 104), and the upper support portion 104 is pressed toward the lower support portion 101 by the pressing portion 303 as shown in FIG. 5A. (S105). The knurled bolt 105 is turned to fasten and fix the upper support portion 104 to the upper frame 103 (S106). As shown in FIG. 5B, after the pressing by the pressing portion 303 is released (S107), the positioning member 106 is removed from the work holder 100, and the center shaft 110 is extracted from below (S108). The work holder 100 is attached to the polishing apparatus 1 shown in FIG. 1, and the inner peripheral end face of the laminated glass substrate 10 is polished (S109).

  And the glass substrate which finished the end surface grinding | polishing process was washed with water. By this end face polishing step, the end face of the glass substrate was processed into a mirror state that can prevent the precipitation of sodium and potassium. In particular, the inner peripheral end face was in a good state without a decrease in tolerance and roundness of the inner hole even when a large number of about 200 to 300 sheets were laminated and polished.

(5) Main surface polishing step As the main surface polishing step, first, a 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. As the abrasive, cerium oxide abrasive grains were used.

  The glass substrate which finished this 1st grinding | polishing process was immersed in each washing tank of neutral detergent, a pure water, and IPA (isopropyl alcohol) one by one, and was wash | cleaned.

  Next, a second polishing step was performed as the main surface polishing step. The purpose of this second polishing step is to finish the main surface into a mirror surface. In the second polishing step, mirror polishing of the main surface was performed using a soft foamed resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, cerium oxide abrasive grains finer than the cerium oxide abrasive grains used in the first polishing step were used.

  The glass substrate which finished this 2nd grinding | polishing process was immersed in each washing tank of neutral detergent, a pure water, and IPA (isopropyl alcohol) sequentially, and was wash | cleaned. Note that ultrasonic waves were applied to each cleaning tank.

(6) Chemical strengthening process Next, the glass substrate which finished the above-mentioned lapping process and polishing process was chemically strengthened. For chemical strengthening, a chemical strengthening solution prepared by mixing potassium nitrate (60%) and sodium nitrate (40%) is prepared, and the chemically strengthened solution is heated to 400 ° C., and the cleaned glass substrate is preheated to 300 ° C. And was immersed in the chemical strengthening solution for about 3 hours. In this immersion, in order to chemically strengthen the entire surface of the glass substrate, it was performed in a state of being housed in a holder so that a plurality of glass substrates were 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 replaced with sodium ions and potassium ions in the chemical strengthening solution, respectively, and the glass substrate is strengthened. The thickness of the compressive stress layer formed on the surface layer of the glass substrate was about 100 μm to 200 μm.

  The glass substrate that had been subjected to the chemical strengthening treatment was immersed in a 20 ° C. water bath and rapidly cooled, and maintained for about 10 minutes. And the glass substrate which finished quenching was immersed in the concentrated sulfuric acid heated at about 40 degreeC, and was wash | cleaned. Further, the glass substrate after the sulfuric acid cleaning was cleaned by immersing in a cleaning bath of pure water and IPA (isopropyl alcohol) sequentially.

  As described above, a flat and smooth, high-rigidity magnetic disk is obtained by performing the first lapping step, the cutting step, the end surface polishing step, the second lapping step, the first and second polishing steps, and the chemical strengthening step. A glass substrate was obtained.

(7) Magnetic disk manufacturing process On both surfaces of the glass substrate obtained through the above-described processes, an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoTaZr-based alloy, an underlayer made of Ru, and a CoCrPt group on the surface of the glass substrate A perpendicular magnetic recording disk was manufactured by sequentially forming a perpendicular magnetic recording layer made of an alloy, a protective layer made of hydrogenated carbon, and a lubricating layer made of perfluoropolyether. Although this configuration is an example of a configuration of a perpendicular magnetic disk, a magnetic layer or the like may be configured as an in-plane magnetic disk.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. 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.

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

It is a figure explaining an inner peripheral end surface grinding | polishing apparatus. It is a figure explaining a work holder. It is a figure explaining a work holder. It is a figure explaining the jig | tool for workpiece holders. It is a figure explaining the process of hold | maintaining a glass substrate using the jig | tool for work holders. It is a flowchart explaining the operation | work at the time of making a work holder hold | maintain a glass substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Polishing apparatus 10 ... Glass substrate 100 ... Work holder 101 ... Lower side support part 101a ... Lower surface 101b ... Hole 102 ... Strut 103 ... Upper frame 103a ... Hole 103b ... Boss hole 104 ... Upper support part 104a ... Hole 104b ... Deformation hole 104c ... Boss hole 105 ... Knurled bolt 105b ... Deformation hole 106 ... Positioning member 106a ... Fitting hole 106b ... Pin 106c ... Step part 110 ... Center shaft 110a ... Main shaft part 110b ... Base part 111 ... Lower spacer 112 ... Upper spacer 113 ... Spacer 201 ... Table 202 ... Base 203 ... Brush 204 ... Brush shaft 205 ... Drive shaft 206 ... Brush lower end support part 207 ... Nozzle 208 ... Bolt 300 ... Work holder jig 301 ... Frame 302 ... Base 303 ... Pressing part 304 ... Pusher

Claims (4)

A work holder that fixes the position of the plurality of laminated glass substrates by sandwiching the plurality of laminated glass substrates between an upper plate and a lower plate and connecting the upper plate and the lower plate at a connecting portion. The upper and lower plates of the work holder are maintained so that the upper plate and the lower plate at both ends of the plurality of glass substrates are maintained parallel to each other. Pressing at least one of the plates against the other side,
The upper plate and the lower plate are connected by a connecting portion,
A method of manufacturing a glass substrate for a magnetic disk, comprising polishing an end surface of a glass substrate sandwiched between the upper plate and the lower plate and fixed to a work holder. A lower support part, an upper frame connected to the lower support part, and an upper support part fastened and fixed to the upper frame, and a plurality of sheets between the lower support part and the upper support part A jig for holding a glass substrate on a work holder that holds the glass substrate in a stacked state,
A platform on which the work holder can be placed in an upright state;
A pressing portion that presses the upper support portion of the work holder toward the lower support portion so that the upper support portion and the lower support portion are maintained in a mutually parallel state. Work holder jig.   The work holder jig according to claim 1, wherein the pressing portion includes an air cylinder. A glass comprising a lower support portion, an upper frame connected to the lower support portion, and an upper support portion fastened and fixed to the upper frame, and a plurality of layers laminated by inserting a center shaft into a central inner hole In the work holder that holds the substrate between the lower support portion and the upper support portion,
A positioning member having a fitting hole for fitting with the center shaft;
The positioning member is provided with a pin or boss hole extending in the axial direction of the center shaft,
The upper support part is provided with a boss hole or pin extending in the axial direction of the center shaft,
The work holder, wherein the pin or boss hole of the positioning member can be inserted into and removed from the boss hole or pin of the upper support part.

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