JP6353524B2 - Substrate manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a substrate used for a magnetic disk or a substrate made of glass , and more specifically, to a method for manufacturing a substrate for a magnetic disk including an end surface polishing treatment of the substrate.

  Today, a personal computer, a notebook personal computer, a DVD (Digital Versatile Disc) recording device, or the like has a built-in hard disk device for data recording. In particular, in a hard disk device used for portable equipment such as a notebook personal computer, a magnetic disk having a magnetic layer provided on a nonmagnetic magnetic disk substrate is used. For example, a glass substrate is used as the magnetic disk substrate.

  In this magnetic disk, the surface of the magnetic disk is used in order to prevent the malfunction of the reproduction due to the thermal asperity failure of the magnetic disk or to prevent the reproduction from becoming impossible. It must be finished to a very smooth and highly cleaned surface free of foreign matter.

  As a cause of foreign matter adhering to the surface of the glass substrate for magnetic disks, not only the surface shape of the main surface of the glass substrate but also the surface shape of the end surface of the glass substrate are considered. That is, if the surface shape of the end face of the magnetic disk substrate is not smooth, the end face rubs against the wall surface of the resin case and the like, and resin or glass fine particles (particles) are generated by this rub. Such fine particles and fine particles in the atmosphere are captured and accumulated on the end face of the magnetic disk glass substrate. The fine particles accumulated on the end surface of the magnetic disk glass substrate become a source of dust generation in a later process or after being mounted on a hard disk device, causing foreign matter to adhere to the surface of the disk substrate.

In general, the end surface of a magnetic disk glass substrate is polished using a polishing brush and a polishing slurry, but this polishing has a low polishing power and a low processing rate, and it is difficult to produce a large number of magnetic disk glass substrates in a short time. was difficult. On the other hand, a method of polishing a glass substrate for a magnetic disk by applying a magnetic field to a magnetic slurry containing magnetic particles and abrasive grains is also known (Patent Document 1).
Specifically, in the method of polishing by applying a magnetic field to the magnetic slurry, in the step of polishing the inner peripheral end surface of the circular hole at the center of the magnetic disk glass substrate, which is the material of the magnetic disk glass substrate, A magnetic field is formed on the inner circumferential side, the magnetic slurry is held in the circular hole by the magnetic field, and the magnetic field is moved with respect to the end surface on the inner circumferential side of the circular hole. The end surface on the inner peripheral side of the circular hole is polished by a magnetic polishing method.
More specifically, since the paired magnets are provided on the outer side of the magnetic disk glass substrate and the inner peripheral side of the circular hole, the lines of magnetic force formed by the paired magnets are the diameter of the magnetic disk glass substrate. Along the direction.

JP 2005-50501 A

However, in the above-described magnetic polishing of the magnetic disk glass substrate, magnets are provided on the outer peripheral side in addition to the inner peripheral side of the circular hole of the magnetic disk glass substrate. The distance between and becomes large, and the magnetic slurry cannot be maintained sufficiently. As a result, there is a problem that the polishing rate is low and the surface roughness of the inner end face to be polished cannot be reduced efficiently.
The end surface of the magnetic disk glass substrate has a side wall surface of the glass substrate and a chamfered surface provided between the side wall surface and the main surface. In this end face, when the above-described magnetic polishing method was used, there was a difference in the polishing rate between the side wall surface and the chamfered surface of the glass substrate, and the desired amount of polishing allowance could not be achieved at the same time. For this reason, even if the polishing of the side wall surface is completed, the polishing of the chamfered surface is not completed, and a polishing residue may occur on the chamfered surface. In this case, when the chamfered surface is further polished, the side wall surface is also polished at the same time. Therefore, the dimension of the side wall surface is changed by the polishing, and the target end face shape cannot be achieved. Furthermore, since extra polishing is performed on the side wall surface after the polishing, extra magnetic slurry is used, which is wasteful in manufacturing. Such a problem occurs not only in the glass substrate but also in the end face polishing of a non-magnetic substrate, for example, an aluminum alloy substrate.

Accordingly, an object of the present invention is to provide a substrate manufacturing method capable of adjusting a polishing rate ratio between a side wall surface and a chamfered surface of a substrate in an end surface polishing process of a glass substrate or a magnetic disk substrate. To do.

According to one embodiment of the present invention, a magnetic function including abrasive grains and magnetic particles is provided on an end surface having a side wall surface of a disk-shaped substrate and a chamfered surface provided between the side wall surface and the main surface of the substrate. look including an end face polishing process of polishing simultaneously with sexual fluids, a method of manufacturing a substrate for manufacturing a magnetic disk substrate. In the manufacturing method, before the end surface polishing treatment, the ratio of the abrasive grains to the grain size of the magnetic particles and the magnetic functional fluid having the magnetic grains and the abrasive grains of the grain size ratio are used. The relationship between the polishing rate ratio of the chamfered surface of the substrate to the polishing rate of the side wall surface of the substrate when the end surface is polished is acquired in advance, and the side wall surface and the chamfered surface of the substrate to be subjected to the end surface polishing process From the ratio of the target polishing rate between the above, the value of the particle size ratio is set, and a magnetic functional fluid having magnetic particles and polishing abrasive grains having the set particle size ratio value is prepared,
In the end surface polishing process,
Forming a mass of the magnetic functional fluid by means of magnetism,
The end surface of the substrate is polished by relatively moving the end surface of the substrate to be subjected to the end surface polishing process in contact with the lump.
According to another aspect of the present invention, an end surface having a side wall surface of a disk-shaped substrate made of glass and a chamfered surface provided between the side wall surface and the main surface of the substrate is formed of abrasive grains and magnetic It is a manufacturing method of a substrate including an end surface polishing process which polishes simultaneously using magnetic functional fluid containing particles. In the manufacturing method,
Prior to the end surface polishing treatment, the end surface of the substrate was polished using a magnetic functional fluid having a particle size ratio of the abrasive grains to the particle size of the magnetic particles and a magnetic particle having the particle size ratio and the abrasive grains. A relationship between a polishing rate ratio of the substrate chamfered surface to a polishing rate of the substrate side wall surface is obtained in advance, and a target between the side wall surface and the chamfered surface of the substrate to be subjected to the end surface polishing process; From the ratio of the polishing rate to be set, the value of the particle size ratio is set, and a magnetic functional fluid having magnetic particles and polishing abrasive grains having the set particle size ratio value is prepared,
In the end surface polishing process,
Forming a mass of the magnetic functional fluid by means of magnetism,
The end surface of the substrate is polished by relatively moving the end surface of the substrate to be subjected to the end surface polishing process in contact with the lump.

In the end surface polishing process, a magnetic force generating means is used to form magnetic lines of force that proceed in the thickness direction of the substrate that is the target of the end surface polishing process, and the magnetic functional fluid prepared is disposed on the magnetic line of force. The functional fluid is held along the magnetic lines of force, and the end surface of the substrate to be subjected to end surface polishing is moved relative to the magnetic functional fluid held by the magnetic lines of force to move the end surface of the substrate. It is preferable to polish.
It is preferable that the particle size ratio in the magnetic functional fluid used for the end surface polishing treatment is 0.6 or less.

In another embodiment of the present invention, an end surface having a side wall surface of a disk-shaped substrate and a chamfered surface provided between the side wall surface and the main surface of the substrate is provided with abrasive grains and magnetic particles. look including an end face polishing process of polishing simultaneously with a magnetic functional fluid comprising a method of manufacturing a substrate for manufacturing a magnetic disk substrate. In the end surface polishing treatment of the manufacturing method,
Forming a mass of the magnetic functional fluid by means of magnetism,
The end surface of the substrate to be subjected to the end surface polishing process is relatively moved while being in contact with the lump. At this time, the particle size ratio of the abrasive grains to the particle size of the magnetic particles in the magnetic functional fluid used in the end face polishing treatment is 0.6 or less.
Furthermore, according to another embodiment of the present invention, an end surface having a side wall surface of a disk-shaped substrate made of glass and a chamfered surface provided between the side wall surface and the main surface of the substrate is provided with abrasive grains. This is a method for manufacturing a substrate including an end surface polishing process in which a magnetic functional fluid including magnetic particles is simultaneously polished. In the end surface polishing treatment of the manufacturing method,
Forming a mass of the magnetic functional fluid by means of magnetism,
Polishing the end surface of the substrate by moving the end surface of the substrate to be subjected to the end surface polishing process in a state of being in contact with the lump,
The particle size ratio of the abrasive grains to the particle size of the magnetic particles in the magnetic functional fluid used in the end surface polishing treatment is 0.6 or less.

In the end surface polishing process, a magnetic force generating means is used to form magnetic lines of force that proceed in the thickness direction of the substrate that is the target of the end surface polishing process, and the magnetic functional fluid prepared is disposed on the magnetic line of force. The functional fluid is held along the magnetic lines of force, and the end surface of the substrate to be subjected to end surface polishing is moved relative to the magnetic functional fluid held by the magnetic lines of force to move the end surface of the substrate. It is preferable to polish.
In addition, it is preferable that the said particle size ratio in the said magnetic functional fluid used for the said end surface grinding | polishing process shall be 0.1 or more.

  The average particle diameter d50 of the abrasive grains is preferably in the range of 0.1 to 10 μm.

  The average particle diameter d50 of the magnetic particles is preferably in the range of 0.5 to 20 μm.

  It is preferable that a relative speed of a peripheral speed of the substrate with respect to the magnetic functional fluid at a contact position between the substrate and the magnetic functional fluid is 50 to 500 m / min.

According to the above-described substrate manufacturing method, the ratio of the polishing rate between the side wall surface and the chamfered surface of a substrate such as a magnetic disk substrate or a glass substrate can be adjusted.

(A)-(c) is a figure explaining the polisher used for the end face polish processing of this embodiment. It is a figure explaining the end surface grinding | polishing process of this embodiment. It is a figure which shows an example of the relationship between the particle size ratio of the abrasive grain with respect to the magnetic particle used by the end surface grinding | polishing process of this embodiment, and the ratio of the polishing rate of the chamfering surface with respect to a side wall surface. It is a figure explaining the polishing allowance measured in order to obtain the ratio of the polishing rate used by this embodiment. It is a figure which shows an example of the index | index of the polishing rate of the side wall surface of this embodiment. It is a figure explaining the example which performs the end surface grinding | polishing process of the inner peripheral side end surface and outer peripheral side end surface of a glass substrate simultaneously among the end surface grinding | polishing processes of this embodiment.

Hereafter, the manufacturing method of the board | substrate of this invention is demonstrated in detail.
The inventor of the present application variously changed the conditions of this polishing in the end surface polishing process in which the side wall surface and the chamfered surface are simultaneously polished using a magnetic functional fluid containing abrasive grains and magnetic particles in the space where the magnetic field lines are generated. However, as a result of investigating the amount of polishing allowance between the side wall surface and the chamfered surface, it was found that the amount of polishing allowance varies depending on the particle size ratio between the abrasive grains and the magnetic particles. Based on this knowledge, the following technique was conceived.

(Magnetic disk and glass substrate for magnetic disk)
The magnetic disk of this embodiment forms a ring shape in which a disk-shaped central portion is hollowed out concentrically, and rotates around the center of the ring. This magnetic disk includes at least a nonmagnetic substrate for a magnetic disk and a magnetic layer. In this embodiment, a glass substrate is used as the nonmagnetic substrate, but an aluminum alloy substrate can also be used. In addition to the magnetic layer, for example, an adhesion layer, a soft magnetic layer, a nonmagnetic underlayer, a perpendicular magnetic recording layer, a protective layer, a lubricating layer, and the like are formed on a glass substrate. For the adhesion layer, for example, a Cr alloy or the like is used. The adhesion layer functions as an adhesion layer with the glass substrate. For the soft magnetic layer, for example, a CoTaZr alloy or the like is used. As the nonmagnetic underlayer, for example, a granular nonmagnetic layer is used. For example, a granular magnetic layer is used for the perpendicular magnetic recording layer. A material made of hydrogen carbon is used for the protective layer. For the lubricating layer, for example, a fluorine-based resin or the like is used.
The glass substrate used for the magnetic disk also has a ring shape in which the central part of the disk shape is cut out concentrically. The inner peripheral side end surface and the outer peripheral side end surface of the glass substrate include a side wall surface and a chamfered surface. The side wall surface is a surface that extends perpendicularly to the main surface of the glass substrate in a cross-sectional view. Two chamfered surfaces are provided between the side wall surface and the main surface in a cross-sectional view, are inclined with respect to the side wall surface, and extend linearly or arcuately toward the main surface. The chamfered surface may be a combination of a linear shape and an arc shape in a sectional view.
There is no restriction | limiting in particular about the diameter of the glass substrate for magnetic discs, A glass substrate can be used for the board | substrate of a nominal 1.8-3.5 inch size, for example. There is no restriction | limiting in particular also about plate | board thickness, For example, it can be 0.3-3 mm.

  Aluminosilicate glass, soda lime glass, borosilicate glass, or the like can be used as the material for the magnetic disk glass substrate in the present embodiment. In particular, aluminosilicate glass can be suitably used in that it can be chemically strengthened and a glass substrate for a magnetic disk excellent in the flatness of the main surface and the strength of the substrate can be produced.

Although it does not limit the composition of the glass substrate for magnetic disks of this embodiment, when converted into an oxide standard as an aluminosilicate glass, SiO ₂ is 50 to 75% and Al ₂ O ₃ in terms of mol%. More than 0% and not more than 15%, at least one component selected from Li ₂ O, Na ₂ O and K ₂ O in total 12 to 35%, at least selected from MgO, CaO, SrO, BaO and ZnO 0-20% of one component in total, _{and, ZrO 2, TiO 2, La} 2 O 3, Y 2 O 3, Ta 2 O 5, Nb 2 O 5 and at least one selected from HfO ₂ of It is preferable to use an aluminosilicate glass having a composition having a total of 0 to 10% of the components.
Further, the glass substrate of the present embodiment is composed of 57 to 75% SiO ₂ , 5 to 20% Al ₂ O ₃ in mass% display as disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-99239, ( However, the total amount of SiO ₂ and Al ₂ O ₃ is 74% or more), ZrO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , La ₂ O ₃ , Y ₂ O ₃ and TiO ₂ in total 0 % More than 6% or less, Li ₂ O more than 1% 9% or less, Na ₂ O 5 to 18% (where the mass ratio Li ₂ O / Na ₂ O is 0.5 or less), K ₂ O 0 to 6%, MgO 0-4%, CaO more than 0% and 5% or less (however, the total amount of MgO and CaO is 5% or less, and the content of CaO is larger than the content of MgO), SrO + BaO May be an amorphous aluminosilicate glass having a composition of 0 to 3%

(End face polishing treatment)
FIG. 1A to FIG. 1C are diagrams for explaining an apparatus used for an end surface polishing process which is one of the glass substrate manufacturing methods of the present embodiment, and FIG. 2 shows an end surface polishing of the present embodiment. It is a figure explaining a process. The example of FIG. 2 illustrates the polishing of the inner peripheral side end face of the glass substrate. About end surface grinding | polishing, the grinding | polishing of the outer peripheral side end surface of a glass substrate can also be applied by the same method.
In the end surface polishing process, a mass of a magnetic functional fluid, which will be described later, is formed by the magnetism generating means, and the end surface of the substrate to be subjected to the end surface polishing process is relatively moved while being in contact with the lump. To polish.
At this time, the magnetic force generation means is used to form a magnetic force line that proceeds in the thickness direction of the substrate to be subjected to the end surface polishing treatment, and the magnetic functional fluid produced is arranged on the magnetic force line, thereby allowing the magnetic functional fluid to be drawn into the magnetic force line. Then, the end face of the substrate is polished by moving the end face of the substrate to be subjected to the end face polishing process in a state of being in contact with the magnetic functional fluid held by the magnetic lines of force.
The outline of the apparatus 10 that performs end surface polishing will be described. As shown in FIG. 1A, the apparatus 10 includes a pair of magnets 12 and 14 that are permanent magnets, and a spacer 16, and extends in one direction. It has a rotating body shape. A spacer 16 is provided between the magnet 12 and the magnet 14. The glass substrate 11 for end face polishing is held by a holder (not shown). The apparatus 10 is passed through a circular hole of the glass substrate 11 held by the holder, and a magnetic functional fluid mass 20 (see FIGS. 1C and 2) containing magnetic particles and abrasive grains, which will be described later, The inner peripheral side end surface of the glass substrate 11 is brought into contact. The magnetic functional fluid is a toroidal mass 20 around the device 10. At this time, the glass substrate 11 is disposed so that the central axis of the glass substrate 11 and the central axes of the magnets 12 and 14 and the spacer 16 of the apparatus 10 are in the same direction. A holder (not shown) that holds the device 10 and the glass substrate 11 is mechanically connected to a drive motor (not shown). The rotating body-shaped device 10 and the holder for the glass substrate 11 rotate around their respective central axes to relatively move the end surface of the glass substrate 11 and the lump 20. As shown in FIG. 2, the rotation direction of the end surface of the glass substrate 11 and the lump 20 may be the same direction or the reverse direction. Thereby, the inner peripheral side end surface of the glass substrate 11 can be grind | polished. An exterior member may be provided so as to cover the magnets 12 and 14 and the spacer 16. In the example shown in FIG. 2, the central axis of the glass substrate 11 and the central axis of the device 10 are offset, but the central axis of the glass substrate 11 and the central axis of the device 10 may coincide with each other.

  When polishing the inner peripheral side end face of the glass substrate 11, the mass of the magnetic functional fluid 20 is rotated by the rotation around the central axis of the apparatus 10, while the glass substrate 11 is also rotated around the central axis. At this time, the relative speed of the peripheral speed of the glass substrate 11 with respect to the magnetic slurry lump 20 at the contact position between the glass substrate 11 and the magnetic functional fluid lump 20 is 50 to 500 m / min in order to efficiently polish the end face. More preferably, the relative speed is 200 to 400 m / min. The entire circumference of the inner peripheral side end face of the glass substrate 11 and the entire circumference of the lump 20 can be brought into contact with each other and rotated. Since the mass 20 of the magnetic functional fluid is formed in an annular shape, the inner peripheral side end surface that is the inner wall surface of the circular through hole of the glass substrate 11 is polished so as not to deform the shape of the circular hole. Can do. In this case, it is preferable that the rotation speed of the glass substrate 11 is, for example, 500 to 4000 rpm, and the rotation speed of the lump 20 is, for example, 50 to 300 rpm. As will be described later, also when the outer peripheral side end surface of the glass substrate 11 is polished, the rotation speed of the glass substrate 11 is preferably 500 to 4000 rpm, and the rotation speed of the lump 20 is preferably 50 to 300 rpm, for example. With such a rotational speed, end face polishing can be performed efficiently.

The rotation direction of the glass substrate 11 and the rotation direction of the lump 20 are preferably opposite to each other at the contact position between the glass substrate 11 and the lump 20 in terms of efficiently performing the end surface polishing treatment. On the other hand, from the viewpoint of reducing the surface unevenness of the end face after the end face polishing treatment, the rotation direction of the glass substrate 11 and the rotation direction of the lump 20 are preferably the same direction at the contact position of the glass substrate 11 and lump 20.
In addition, as long as the end surface of the glass substrate 11 and the lump 20 can be relatively moved, the glass substrate 11 may be rotated without rotating the lump 20.

  More specifically, the end face polishing will be described. The magnet 12 and the magnet 14 are close to each other and function as magnetism generating means to form a magnetic force line 19 as shown in FIG. A part of the lines of magnetic force 19 proceeds linearly from the centers of the magnets 12 and 14 and proceeds in the thickness direction of the glass substrate 11. Further, a part of the magnetic force lines 19 proceeds so as to protrude outward from the centers of the magnets 12 and 14 and proceeds in the thickness direction of the glass substrate 11. In the example shown in FIG. 1B, a pair of magnets arranged in the thickness direction of the glass substrate 11 so that the N-pole surface and the S-pole surface face each other are used as the magnetism generating means. It is done. Faces facing each other means that the faces face each other in parallel, that is, face each other. A spacer 16 made of a non-magnetic material is provided between the magnets 12 and 14 so that the separation distance between the N pole end face of the magnet 12 and the S pole end face of the magnet 14 is a predetermined distance. It is done. The distance between the N pole end face of the magnet 12 and the S pole end face of the magnet 14 is set to a predetermined distance because a part of the lines of magnetic force 19 are connected to the magnet 12 as shown in FIG. In addition to advancing the concave groove between the magnets 14 downward in the drawing, a part of the magnetic field lines 19 are protruded to the outside of the magnets 12 and 14 so that the magnetic slurry as shown in FIG. This is because the lump 20 is formed along the outer periphery of the device 10. Since the lump 20 is a portion that contacts the end surface of the glass substrate 11 and moves relative to the end surface, the lump 20 is desired to have a certain degree of magnetic force from the viewpoint of securing the rigidity of the lump 20. For this reason, it is preferable that the separation distance between the N pole end face of the magnet 12 and the S pole end face of the magnet 14 is short, but if the separation distance is excessively short, the lump 20 cannot be sufficiently formed. . For this reason, the separation distance between the end face of the N pole of the magnet 12 and the end face of the S pole of the magnet 14 is set to a certain predetermined range.

In the end surface polishing of the glass substrate of the present embodiment, it is preferable that the end surface of the glass substrate 11 is polished by being pressed into the lump 20 in a direction orthogonal to the lines of magnetic force in order to increase the polishing rate. By pressing in the direction perpendicular to the magnetic field lines, the end surface of the glass substrate 11 receives a large drag force from the lump 20, so that polishing is promoted.
The end surface of the glass substrate 11 of the present embodiment has a magnetic field line connecting the N pole of the magnet 12 and the S pole of the magnet 14 inside the magnetic slurry lump 20, that is, the magnetic field line extends from the N pole or from the S pole. It is pressed into the interior of the mass 20 so as to come into contact with the part held by the magnetic field lines ending at the pole or N pole. The portion of the magnetic slurry held along the magnetic field lines connecting the N pole of the magnet 12 and the S pole of the magnet 14 has higher rigidity and realizes a higher polishing rate than the portion where the magnetic field lines do not end at the poles of the magnet. On the other hand, the main surface of the glass substrate 11 is in contact with the portion of the lump 20 having a low rigidity that is mostly blocked by the glass substrate 11 and held by magnetic lines that do not reach the poles of the magnet. Even if the main surface contacts, it is hardly polished.
The lump 20 may be formed in a concave groove having the outer peripheral surface of the spacer 16 as a groove bottom surface and the end surfaces of the magnets 12 and 14 as side wall surfaces, and the end surface of the glass substrate may be pressed into the lump 20 in the groove. However, as shown in FIG.1 (c), it protrudes from the recessed part between the magnets 12 and 14, and the end surface of a glass substrate may be pressed in this protrusion part.

  As described above, the glass substrate 11 is pushed into the lump 20 so that the side wall surface and the chamfered surface are polished simultaneously. At this time, the portion of the main surface of the glass substrate that contacts the lump 20 is substantially polished. Not.

  In the examples shown in FIGS. 1A to 1C and FIG. 2, a permanent magnet is used as the magnetism generating means, but an electromagnet can also be used. Further, the spacer 16 is used in order to ensure a certain distance between the N pole end face of the magnet 12 and the S pole end face of the magnet 14, but the exterior member (not shown) is used without using the spacer 16. Further, the magnets 12 and 14 are fixed to each other, and a constant separation distance between the N pole end face of the magnet 12 and the S pole end face of the magnet 14 can be secured.

As the magnetic functional fluid used for end face polishing, for example, a nonpolar oil containing ³ to 5 g / cm ^{3 of} magnetic particles made of Fe and a magnetorheological fluid containing a surfactant are used. In this specification, it becomes a magnetic functional fluid by including abrasive grains in this magnetorheological fluid. Nonpolar oil or polar oil has a viscosity of 100 to 1000 (mPa · sec) at room temperature (20 ° C.), for example. The average particle diameter d50 (diameter) of the magnetic particles is preferably 2.0 to 7.0 μm in that the ratio of the chamfered surface polishing rate to the side wall surface can be suitably adjusted as described later. . The average particle size d50 is the median value of the particle size distribution.
The lump 20 formed by the magnetic functional fluid includes abrasive grains as well as the magnetic particles when the magnetic functional fluid is formed as a lump on the lines of magnetic force. Since the abrasive grains in the magnetic functional fluid are pushed out to a portion having a low magnetic force gradient due to the magnetic levitation effect, the abrasive grains are present in the vicinity of the end face of the glass substrate to be polished. And since it becomes a lump which has a comparatively high elastic characteristic with a magnetic force line, it can grind | polish efficiently by pressing the end surface of a glass substrate to the lump 20. That is, the polishing rate can be increased and polishing can be performed efficiently.

  As abrasive grains contained in the magnetic functional fluid, known abrasive grains of glass substrates such as cerium oxide, colloidal silica, zirconia oxide, alumina abrasive grains, diamond abrasive grains, silica abrasive grains, and SiC abrasive grains may be used. it can. As for the particle size of the abrasive grains, for example, 0.4 to 3.0 μm can suitably adjust the ratio of the chamfered surface polishing rate to the side wall surface, and efficiently obtain a high-quality surface. It is preferable at the point which can do. By using abrasive grains in this range, the inner peripheral side end face of the glass substrate can be satisfactorily polished. The abrasive grains are contained, for example, in an amount of 3 to 15 vol% in the magnetic functional fluid. The polishing rate is a value obtained by dividing the polishing allowance by the polishing time. Therefore, if the polishing time is the same, the ratio of the polishing rate and the ratio of the polishing allowance are the same and are synonymous. Therefore, in this case, adjusting the ratio of the polishing rate is also adjusting the ratio of the amount of machining allowance.

  The viscosity of the magnetic functional fluid using the magnetorheological fluid is 1000 to 2000 [mPa · sec] at room temperature (20 ° C.) by adjusting the concentration of the magnetorheological fluid. This is preferable in terms of efficient operation. If the viscosity is low (the concentration of the magnetorheological fluid is low), the lump 20 is difficult to form, and it is difficult to perform the relative movement while being pressed against the end face of the glass substrate 11 for polishing. On the other hand, when the viscosity of the magnetic functional fluid is excessively high, the lump 20 has a shape recessed along the end shape of the glass substrate 11 during polishing, and is difficult to recover from the shape. Since the shape remains strong, it is difficult to form a uniform pressed state. In addition, the magnetic flux density in the magnetism generating means is preferably 0.3 to 2 [Tesla] in that the lump 20 is formed and end face polishing is efficiently performed. In addition, the yield stress of the magnetorheological fluid is preferably 30 kPa or more, more preferably 30 to 60 kPa, with a 0.4 [Tesla] magnetic field applied.

  In the present embodiment, before such end surface polishing treatment, the end surface polishing is performed using the particle size ratio of the abrasive grains to the particle size of the magnetic particles and the magnetic slurry having the magnetic particles and the abrasive grains of this particle size ratio. The relationship between the polishing rate on the chamfered surface of the glass substrate 11 to the polishing rate on the side wall surface of the glass substrate 11 when the processing is performed is acquired in advance. Further, the value of the particle size ratio is set from the ratio of the target polishing rate between the side wall surface and the chamfered surface of the glass substrate 11, and the magnetic function having the magnetic particles and the polishing abrasive grains having the set particle size ratio value A sex fluid is produced. The production of such a magnetic functional fluid has a correlation between the particle size ratio of the abrasive grains to the magnetic particles and the ratio of the chamfered surface polishing rate to the side wall surface. This is because it has been found that the smaller the particle size ratio, the higher the polishing rate ratio.

  FIG. 3 is a diagram showing an example of the relationship between the particle size ratio of the abrasive grains to the magnetic particles and the ratio of the chamfered surface polishing rate to the side wall surface polishing rate. In the example shown in FIG. 3, magnetic particles made of Fe having an average particle diameter d50 (diameter) of magnetic particles of 2 μm, 4 μm, and 7 μm were used, and zirconia abrasive grains were used as the abrasive grains. At this time, the particle size ratio was variously changed by variously changing the average particle size d50 (diameter) of the abrasive grains.

In order to obtain the polishing rate of the side wall surface and the polishing rate of the chamfered surface, as shown in FIG. 4, the cross-sectional shapes of the side wall surface 11a and the chamfered surface 11b of the end surface are measured before and after the end surface polishing process by the contour shape measuring machine. It was measured. From the measured cross-sectional shape, the polishing rate ratio was determined by obtaining the polishing allowances P ₁ and P ₂ at the central portion in the thickness direction of the side wall surface 11a and the central portion along the surface direction of the chamfered surface 11b. . FIG. 4 is a diagram illustrating the amount of machining allowance.

  As can be seen from FIG. 3, substantially the same correlation is exhibited when the average particle diameter d50 (diameter) of the magnetic particles is 2 μm, 4 μm, or 7 μm. From this correlation, the ratio of the polishing rate of the chamfered surface 11b to the side wall surface 11a can be reduced by reducing the particle size ratio (by reducing the particle size of the abrasive grains or by increasing the particle size of the magnetic particles). It can be seen that can be improved. Therefore, when a polishing residue occurs on the chamfered surface 11b, the side wall surface 11a and the chamfered surface 11b can be reduced by reducing the average particle size d50 (diameter) of the abrasive grains or by increasing the particle size of the magnetic particles. Polishing can be performed with substantially the same polishing rate so that no polishing residue occurs.

Thus, the ratio of the polishing rate can be determined using the ratio of the average particle diameter d50 (diameter) of the abrasive grains to the average particle diameter d50 (diameter) of the magnetic particles. Thus, the ratio of the polishing rate between the side wall surface 11a and the chamfered surface 11b is adjusted by changing the average particle size d50 (diameter) of either the magnetic particles or the abrasive grains to adjust the particle size ratio. It can be seen that it can be adjusted.
Such a correlation is confirmed when the average particle diameter d50 (diameter) of the abrasive grains is in the range of 0.1 to 10 μm. Moreover, it has been confirmed when the average particle diameter d50 (diameter) of the magnetic particles is in the range of 0.5 to 20 μm. Among these, when the average particle diameter d50 (diameter) of the abrasive grains is 0.4 to 3.0 μm, the target polishing rate ratio can be achieved more accurately, and a high quality surface can be achieved. The average particle diameter d50 (diameter) of the magnetic particles is preferably from 2.0 to 7.0 μm because it can be efficiently obtained, and the target polishing rate ratio can be achieved more accurately. This is preferable because a high-quality surface can be obtained efficiently.

The generation mechanism of such a relationship is not clear, but is presumed as follows. That is, as shown in FIG. 1C, when the magnetic functional fluid is in the state of the mass 20, the magnetic particles in the magnetic functional fluid form a line of magnetic particles arranged along the lines of magnetic force, and the mass 20 has high rigidity. Have At this time, the abrasive grains are dispersed around the magnetic particles. When the end surface of the glass substrate 11 enters the inside of the lump 20 in this state, the lump 20 is elastically deformed and changes its shape. On the other hand, due to the high rigidity of the mass 20, the end surface of the glass substrate 11 can be pressed against the mass 20, and the end surface of the glass substrate 11 can be pressed into the mass 20 by this pressing force and the relative speed between the mass 20 and the end surface of the glass substrate 11. And the end face is polished. At this time, the larger the grain size of the abrasive grains due to the shape deformation of the lump 20, the greater the force of breaking the magnetic particles into the line, so the line is easier to cut.
Here, since the end surface of the glass substrate 11 enters the lump 20, the magnetic particle line in the lump 20 is deformed so as to be recessed in a valley shape so as to follow the shape of the end face composed of the side wall surface 11a and the chamfered surface 11b. The mass 20 generates a drag toward the end surface of the glass substrate 11. At this time, the region of the magnetic particle line located in the vicinity of the side wall surface 11a in the deformed mass 20 receives the force of the side wall surface 11a from the direction orthogonal to the direction in which the magnetic particle line extends, whereas the chamfering is performed. The region of the line of magnetic particles located in the vicinity of the surface 11b is located along the inclined portion of the line deformed into a valley shape, and thus extends along the direction in which the glass substrate 11 enters. The inclined portion of this line receives a force in the direction in which the glass substrate 11 enters from the glass substrate 11. In particular, when abrasive grains having a large particle size enter the inclined portion of the line located in the vicinity of the chamfered surface 11b, a force directed from the glass substrate 11 toward the entrance direction of the glass substrate 11 is received and the above line is Since the distance between the magnetic particles becomes long, the line is easily cut. For this reason, since the magnetic slurry in this region cannot maintain high rigidity, the force applied to the chamfered surface 11b by the abrasive grains supported by the magnetic particle line is reduced. For this reason, the polishing rate on the chamfered surface 11b tends to be lower than that on the side wall surface 11a. On the other hand, when the grain size of the abrasive grains is small, since the force of the abrasive grains trying to interrupt the line of magnetic particles located in the vicinity of the chamfered surface 11b is weak, the line is hardly cut.
The above can be said even when the particle size of the abrasive grains is constant and the particle size of the magnetic particles changes. Therefore, when the particle size ratio of the abrasive grains to the magnetic particles is increased, the ratio of the chamfered surface 11b to the side wall surface 11a is decreased. When the particle size ratio is decreased, the polishing rate of the chamfered surface 11b to the side wall surface 11a is decreased. The ratio improves and approaches 1.0.

Regarding the surface roughness of the side wall surface 11a and the chamfered surface 11b after the end surface polishing process using such magnetic slurry is performed, the maximum height Rz (JIS B0601: 2001) may be 0.15 μm or less. preferable. Thereby, since the depth of the micro groove | channel which generate | occur | produces in the side wall surface 11a and the chamfering surface 11b becomes shallow, possibility that microparticles will adhere will decrease. The arithmetic average roughness Ra (JIS B0601: 2001) of the side wall surface 11a and the chamfered surface 11b after the end surface polishing treatment is preferably 0.015 μm or less.
Such surface roughness is the maximum height Rz and arithmetic mean roughness Ra when measured under the following conditions in a 50 μm square evaluation region using a laser microscope. At this time, the resolution in the height direction is preferably 1 nm or less. Moreover, what is necessary is just to select observation magnification suitably in the range of about 1000 to 3000 times according to the magnitude | size of a measurement surface.
Observation magnification: 3000 times
Measuring pitch in the height direction (Z axis): 0.01 μm,
Cut-off value λs: 0.25 μm,
Cut-off value λc: 80 μm.

  When the particle size ratio is reduced, the ratio of the chamfered surface 11b to the side wall surface 11a is improved. However, since the particle size of the abrasive grains is reduced, the polishing power is reduced and the value of the polishing rate itself is reduced. To do. FIG. 5 is a diagram showing an example of the index of the polishing rate of the side wall surface 11a. In the example shown in FIG. 5, the average particle diameter d50 (diameter) of the magnetic particles is kept constant at 2 μm, and the average particle diameter d50 (diameter) of the abrasive grains is variously changed. The index of the polishing rate is normalized by setting the polishing rate at a particle size ratio of 1.2 to 1.00 (the higher the index, the higher the polishing rate). As can be seen from FIG. 5, the smaller the particle size ratio, the lower the polishing rate. For this reason, in order not to make the processing time of the end surface polishing treatment of the glass substrate 11 long, the particle size ratio is preferably 0.1 or more, and more preferably 0.2 or more.

  In the manufacturing process of the glass substrate, the side wall surface 11a and the chamfered surface 11b are formed by shape processing in which the end surface of the glass substrate is shaved with a grinding wheel. In many cases, the surface roughness of the side wall surface 11a and the chamfered surface 11b formed by this grinding wheel is approximately the same. For this reason, the polishing allowance required for the side wall surface 11a and the chamfered surface 11b in the end surface polishing process is often substantially the same. Therefore, in this case, it is preferable that the polishing rate of the side wall surface 11a and the chamfered surface 11b is substantially the same in the end surface polishing process. In this respect, the polishing rate ratio between the side wall surface 11a and the chamfered surface 11b is preferably 0.8 or more, and more preferably 0.9 or more. When the ratio of the polishing rate is less than 0.8, the polishing rate on the chamfered surface 11b is extremely lower than the polishing rate on the side wall surface 11a, and when the end surface polishing process is finished according to the polishing allowance on the side wall surface 11a, In some cases, polishing residue is left on the chamfered surface and the surface roughness of the chamfered surface is rough with respect to the target. On the other hand, when the end surface polishing process is completed according to the amount of polishing allowance on the chamfered surface, the time required for the end surface processing is long and the productivity is lowered. Therefore, it is preferable to determine the particle size ratio of the polishing abrasive grains to the magnetic particles using the preferable polishing rate ratio and the correlation shown in FIG. 3 so that the preferable polishing rate ratio is achieved.

  In order to set the polishing rate ratio to 0.8 or more, the particle size ratio is set to 0.6 or less from the correlation shown in FIG. Therefore, in one form of this embodiment, the particle size ratio of the abrasive grains to the particle size of the magnetic particles in the magnetic slurry used in the end face polishing process is 0.6 or less. At this time, the particle size ratio is preferably 0.1 or more, and more preferably 0.2 or more, from the viewpoint that the polishing rate of the side wall surface 11a is not greatly reduced. That is, the polishing of the side wall surface 11a and the chamfered surface 11b can be completed almost simultaneously by setting the particle size ratio to be 0.1 or more and 0.6 or less, and further 0.2 or more and 0.6 or less. In addition, the polishing time is not lengthened, and the end surface polishing treatment of the glass substrate 11 can be performed efficiently.

  Depending on how the side wall surface 11a and the chamfered surface 11b are shaped, there may be a difference in surface roughness between the side wall surface 11a and the chamfered surface 11b immediately after the shape processing. In this case, the polishing allowances of the side wall surface 11a and the chamfered surface 11b are also different. For this reason, the ratio of the polishing rates can be determined according to different polishing allowances, and the particle size ratio can be determined using the correlation shown in FIG. As a result, when end polishing is performed with different polishing allowances for the side wall surface 11a and the chamfered surface 11b, by adjusting the polishing rate ratio, the end of polishing of the side wall surface 11a and the end of polishing of the chamfered surface 11b can be adjusted. Can be aligned.

The end surface polishing process described above is an end surface polishing process on the inner peripheral side end surface of the glass substrate 11, but can also be applied to an end surface polishing process on the outer peripheral side end surface of the glass substrate 11.
FIG. 6 is a diagram for explaining an example in which the end surface polishing processing of the inner peripheral side end surface and the outer peripheral side end surface of the glass substrate 11 is performed simultaneously.
In the example shown in FIG. 6, the inner peripheral side end surface of the glass substrate 11 is polished, and the outer peripheral side end surface of the glass substrate 11 is simultaneously polished. That is, the apparatus 10 in which the lump 20 is formed is passed through a circular through hole provided at the center of the glass substrate 11, and the lump 20 of magnetic slurry and the inner peripheral side end surface of the glass substrate 11 are brought into contact with each other. At the same time, a lump 62 of magnetic slurry is formed on the outer peripheral surface of the spacer (not shown) between the magnets 12 and 14 and the same magnets 60 and 64 as the spacer 16. Magnets 60 and 64 and spacers (not shown) are positioned so that lump 62 is in contact with glass substrate 11. The magnets 60 and 64 and the spacer (not shown) are mechanically connected to a drive motor (not shown) in the same manner as the magnets 12 and 14 and the spacer 16 and are rotatable. Therefore, by rotating the apparatus 10 including the magnets 12 and 14 and the spacer 16 and the apparatus including the magnets 60 and 64 and a spacer (not shown) in a different direction from the glass substrate 11, the inner peripheral side end surface of the glass substrate 11 and The outer peripheral side end face can be polished at the same time, and efficient end face polishing is realized. In the example shown in FIG. 6, the central axis that is the rotational axis of the glass substrate 11 is offset with respect to the central axis that is the rotational axis of the magnets 12, 14 and the spacer 16, and the inner peripheral side of the glass substrate 11. Only a part of the end surface is shown in contact with the lump 20 and is polished. Of course, the central axis that is the rotational axis of the glass substrate 11 may coincide with the central axis that is the rotational axis of the magnets 12, 14 and the spacer 16, and the entire inner peripheral end face of the glass substrate 11 may be uniformly and simultaneously polished.
In such an end surface polishing process, a plurality of glass substrates are arranged along the central axis direction of the apparatus including a magnet and a spacer, and a plurality of lumps 20 and 62 are formed on the outer periphery of the apparatus. The end surfaces of a plurality of glass substrates can also be polished simultaneously by bringing them into contact with different glass substrates.
The side wall surface 11a of the present embodiment extends perpendicular to the main surface of the glass substrate in a cross-sectional view, and the chamfered surface 11b is inclined with respect to the side wall surface in a cross-sectional view and linearly toward the main surface. Although extended, the side wall surface 11a and the chamfered surface 11b may be formed in an arc shape in a sectional view.
In addition, although this embodiment demonstrated the form which carries out the end surface grinding | polishing process of the glass substrate of 1 sheet, the end surface of each laminated substrate of the board | substrate laminated body which laminated | stacked the main surface and bonded together is simultaneously performed by an end surface grinding | polishing process. It can also be polished. In this case, the main surface of the laminated substrate can be attached with an adhesive, such as a thermosetting resin, to form a substrate laminated body. This improves the productivity of the substrate.
The above end surface polishing treatment is performed as one treatment of the glass substrate manufacturing method described below.

(Glass substrate manufacturing method)
Next, the manufacturing method of the glass substrate for magnetic disks of this embodiment is demonstrated. First, a glass blank as a material for a plate-shaped magnetic disk glass substrate having a pair of main surfaces is produced by press molding (press molding process). In this embodiment, the glass blank is produced by press molding. However, even if a glass plate is formed by a well-known float method, redraw method, or fusion method, and a glass blank having the same shape as the glass blank is cut out from the glass plate. Good. Next, a circular hole is formed in the center part of the produced glass blank, and it is set as a ring-shaped (annular) glass substrate (circular hole formation process). Next, shape processing is performed on the glass substrate in which the circular holes are formed (shape processing processing). Thereby, a glass substrate is produced | generated. Next, end-face polishing is performed on the shape-processed glass substrate (end-face polishing process). Grinding is performed on the main surface of the glass substrate that has been subjected to end face polishing (grinding treatment). Next, 1st grinding | polishing is performed to the main surface of a glass substrate (1st grinding | polishing process). Next, chemical strengthening is performed on the glass substrate as necessary (chemical strengthening treatment). Next, the second polishing is performed on the glass substrate (second polishing process). Thereafter, ultrasonic cleaning is performed on the glass substrate after the second polishing process (ultrasonic cleaning process). The glass substrate for magnetic disks is obtained through the above processing. Hereinafter, each process will be described in detail.

(A) Press molding process The front-end | tip part of a molten glass flow is cut | disconnected with a cutter, the cut molten glass lump is pinched | interposed between the press molding surfaces of a pair of metal molds, and a glass blank is formed by pressing. After pressing for a predetermined time, the mold is opened and the glass blank is taken out.

(B) Circular hole formation treatment A disk-shaped glass substrate having a circular hole can be obtained by forming a circular hole in a glass blank using a drill or the like.

(C) Shape processing In the shape processing, chamfering is performed on the end of the glass substrate after the circular hole formation processing. The chamfering process is performed using a grinding wheel or the like. By chamfering, a side wall surface of the substrate that extends perpendicularly to the main surface of the glass substrate on the end surface of the glass substrate, and a chamfer surface that is provided between the side wall surface and the main surface and extends at an angle to the side wall surface. Are formed.

(D) End surface polishing process In the end surface polishing process, the inner end surface and the outer peripheral side end surface of the glass substrate are mirror-finished by the end surface polishing process shown in FIG. 1 using the magnetic functional fluid described above. At this time, the magnetic functional fluid includes abrasive grains such as cerium oxide, zirconium oxide, silicon oxide, and diamond in addition to the magnetic particles. In the end face polishing process, the order of the following grinding process and process may be interchanged.

(E) Grinding process In the grinding process, grinding is performed on the main surface of the glass substrate using a double-sided grinding apparatus having a planetary gear mechanism. Specifically, the main surfaces on both sides of the glass substrate are ground while holding the glass substrate in a holding hole provided in a holding member of a double-side grinding apparatus. The double-sided grinding apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and a glass substrate is sandwiched between the upper surface plate and the lower surface plate. Then, by moving one or both of the upper surface plate and the lower surface plate and relatively moving the glass substrate and each surface plate, both main surfaces of the glass substrate can be ground.

(F) 1st grinding | polishing process Next, 1st grinding | polishing is given to the main surface of the glass substrate of grinding. Specifically, the main surfaces on both sides of the glass substrate are polished while holding the glass substrate in a holding hole provided in a polishing carrier of a double-side polishing apparatus. The purpose of the first polishing is to remove scratches and distortions remaining on the main surface after the grinding treatment, or to adjust minute surface irregularities (microwaveness, roughness).

  In the first polishing process, the glass substrate is polished while applying a polishing slurry by using a double-side polishing apparatus having the same configuration as that of the double-side grinding apparatus used for the grinding process using fixed abrasive grains. In the first polishing process, a polishing slurry containing loose abrasive grains is used. For example, cerium oxide abrasive grains or zirconia abrasive grains are used as the free abrasive grains used in the first polishing. In the double-side polishing apparatus, similarly to the double-side grinding apparatus, the glass substrate is sandwiched between a pair of upper and lower surface plates. An annular flat polishing pad (for example, a resin polisher) is attached to the upper surface of the lower surface plate and the bottom surface of the upper surface plate as a whole. Then, by moving either the upper surface plate or the lower surface plate, or both, the glass substrate and each surface plate are relatively moved, thereby polishing both main surfaces of the glass substrate.

(G) Chemical strengthening treatment When chemically strengthening a glass substrate, for example, a mixed melt of potassium nitrate and sodium sulfate is used as the chemical strengthening solution, and the glass substrate is immersed in the chemical strengthening solution.

(H) Second polishing (final polishing) treatment Next, the glass substrate is subjected to second polishing. The second polishing treatment aims at mirror polishing of the main surface. Also in the second polishing, a double-side polishing apparatus having the same configuration as the double-side polishing apparatus used for the first polishing is used. Specifically, the main surface on both sides of the glass substrate is polished while the outer peripheral side end surface of the glass substrate is held in the holding hole provided in the polishing carrier of the double-side polishing apparatus. The second polishing process is different from the first polishing process in that the type and particle size of the free abrasive grains are different and the hardness of the resin polisher is different. For example, a polishing liquid containing colloidal silica as loose abrasive grains is supplied between the polishing pad of the double-side polishing apparatus and the main surface of the glass substrate, and the main surface of the glass substrate is polished.
In the present embodiment, the chemical strengthening process is performed, but the chemical strengthening process may not be performed if necessary. In addition to the first polishing process and the second polishing process, another polishing process may be added, and the polishing process of the two main surfaces may be performed by one polishing process. Moreover, you may change suitably the order of said each process.

(Example)
In order to confirm the effect of this embodiment, the glass substrate was produced with the following method.
Specifically, the disk-shaped glass blank obtained by the press method was subjected to a circular hole forming process to obtain a disk-shaped glass substrate having a circular hole at the center. The upper and lower main surfaces of the disk-shaped glass plate were ground using a double-side grinding apparatus equipped with a pair of grinding surface plates, and the plate thickness was 0.7 mm. Next, the end surface of this disk-shaped glass plate was subjected to shape processing so that the chamfering width was 0.15 mm and the chamfering angle was 45 ° to obtain an inner peripheral side end surface and an outer peripheral side end surface, and then end surface polishing was performed. did. In the shape processing, first, roughing was performed by grinding without tilting the grindstone using a general-purpose grindstone, and then finishing was performed by helical grinding with an inclination of 3 ° by changing the grindstone.
Then, various end surface grinding | polishing processes were given to the side wall surface and chamfering surface of the glass substrate which carried out the shape processing process. The rotation direction of the end surface of the glass substrate 11 and the lump 20 was set to the same direction at the processing point where the end surface and the lump 20 contacted. In addition, about processes other than an end surface grinding | polishing process, it performed by the content according to said embodiment, and manufactured the glass substrate for magnetic discs.
As a process after the end face polishing process, specifically,
First polishing (performed using cerium oxide (d50: 1 μm) and hard polyurethane polishing pad),
・ Chemical strengthening treatment,
Second polishing (performed using colloidal silica (d50: 30 nm) and a soft polyurethane polishing pad),
・ Cleaning treatment
The glass substrate for a magnetic disk was manufactured in order. The manufactured magnetic disk glass substrate is a magnetic disk glass substrate with a nominal 2.5 inch size having an outer diameter of about 65 mm, an inner diameter of about 20 mm, and a plate thickness of about 0.635 mm.
In the end surface polishing treatment, the average particle diameter d50 of the magnetic particles is fixed to 2 μm, the average particle diameter d50 of the polishing abrasive grains is changed variously, the ratio of the particle diameter is changed, and the ratio of the polishing rate of the side wall surface to the chamfered surface is changed. Asked. In the end surface polishing treatment, the inner peripheral side end surface was a polishing target.
The magnetorheological fluid used had a viscosity of 1000 (mPa · sec) at room temperature (20 ° C.).
Fe particles were used as magnetic particles, and zirconia particles were used as abrasive grains.
The polishing rate ratio was determined from the amount of polishing allowance at the center portion of the side wall surface and the chamfered surface after end surface polishing for 3 minutes.
Table 1 shows the results of the particle size ratio and polishing rate ratio.

  From this, it can be seen that in order to make the polishing rate ratio 0.8 or more so that the side wall surface and the chamfered surface have substantially the same polishing rate, the particle size ratio is preferably 0.6 or less. By setting the particle size ratio to 0.4 or less, the polishing rate ratio can be set to 0.85 or more, which is more preferable. In the polishing of the outer peripheral side end surface, the same result as that of the inner peripheral side end surface was obtained.

Further, the average particle diameter d50 of the magnetic particles was fixed to 5 μm, the average particle diameter d50 of the polishing abrasive grains was variously changed, and the particle size ratio was changed to obtain the index of the polishing rate of the side wall surface. As an index of the polishing rate, the polishing rate of Sample 8 having a particle size ratio described later of 1.20 was set to 1.00. The index of the polishing rate means that the smaller the value of the polishing rate, the smaller the index.
Fe particles were used as magnetic particles, and zirconia particles were used as abrasive grains.
The polishing rate ratio was determined from the amount of polishing allowance at the center portion of the side wall surface and the chamfered surface after end surface polishing for 3 minutes.
Table 2 shows the results of the particle size ratio and polishing rate ratio.

  From Table 2, it can be seen that when the particle size ratio is reduced, the polishing rate of the side wall surface decreases. In order to ensure that the index of the polishing rate of the side wall surface is 0.80 or more, the particle size ratio is preferably 0.1 or more. In particular, in order to efficiently perform the end face polishing treatment, the particle size ratio is more preferably 0.2 or more.

Although the substrate manufacturing method of the present invention has been described in detail above, the present invention is not limited to the above-described embodiments and modifications, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course.

10 apparatus 11 glass substrate 11a side wall surface 11b chamfered surface 12, 14 magnet 16 spacer 20, 62 lump

Claims (8)

Polishing simultaneously the end surface which has the side wall surface of a disk-shaped board | substrate, and the chamfering surface provided between the said side wall surface and the main surface of the said board | substrate using the magnetic functional fluid containing an abrasive grain and a magnetic particle. A substrate manufacturing method for manufacturing a magnetic disk substrate, comprising:
Prior to the end surface polishing treatment, the end surface of the substrate was polished using a magnetic functional fluid having a particle size ratio of the abrasive grains to the particle size of the magnetic particles and a magnetic particle having the particle size ratio and the abrasive grains. A relationship between a polishing rate ratio of the substrate chamfered surface to a polishing rate of the substrate side wall surface is obtained in advance, and a target between the side wall surface and the chamfered surface of the substrate to be subjected to the end surface polishing process; From the ratio of the polishing rate to be set, the value of the particle size ratio is set, and a magnetic functional fluid having magnetic particles and polishing abrasive grains having the set particle size ratio value is prepared,
In the end surface polishing process,
Forming a mass of the magnetic functional fluid by means of magnetism,
A method for manufacturing a substrate, comprising: polishing an end surface of a substrate by relatively moving an end surface of the substrate to be subjected to an end surface polishing process in contact with the lump. An end surface having a side wall surface of a disk-shaped substrate made of glass and a chamfered surface provided between the side wall surface and the main surface of the substrate is used with a magnetic functional fluid containing abrasive grains and magnetic particles. A method of manufacturing a substrate including an end surface polishing process for polishing simultaneously,
Prior to the end surface polishing treatment, the end surface of the substrate was polished using a magnetic functional fluid having a particle size ratio of the abrasive grains to the particle size of the magnetic particles and a magnetic particle having the particle size ratio and the abrasive grains. A relationship between a polishing rate ratio of the substrate chamfered surface to a polishing rate of the substrate side wall surface is obtained in advance, and a target between the side wall surface and the chamfered surface of the substrate to be subjected to the end surface polishing process; From the ratio of the polishing rate to be set, the value of the particle size ratio is set, and a magnetic functional fluid having magnetic particles and polishing abrasive grains having the set particle size ratio value is prepared,
In the end surface polishing process,
Forming a mass of the magnetic functional fluid by means of magnetism,
A method for manufacturing a substrate, comprising: polishing an end surface of a substrate by relatively moving an end surface of the substrate to be subjected to an end surface polishing process in contact with the lump.   The method for manufacturing a substrate according to claim 1 or 2, wherein the particle size ratio in the magnetic functional fluid used for the end face polishing treatment is 0.6 or less. The particle size ratio in the magnetic functional fluid used in the end face polishing process, and 0.1 above, in the method of manufacturing a substrate according to any one of claims 1-3. The method for manufacturing a substrate according to any one of claims 1 to 4 , wherein an average particle diameter d50 of the abrasive grains is in a range of 0.1 to 10 µm. The average particle size d50 of the magnetic particles is in the range of 0.5 to 20 [mu] m, the manufacturing method of the substrate according to any one of claims 1-5. The method for manufacturing a substrate according to any one of claims 1 to 6 , wherein a relative speed of a peripheral speed with respect to the lump of the substrate at a contact position between the substrate and the magnetic functional fluid is 50 to 500 m / min. The said board | substrate is each laminated substrate of the board | substrate laminated body which affixed main surfaces and laminated | stacked two or more sheets, Comprising: In the said end surface grinding | polishing process, the end surface of each laminated substrate of the said board | substrate laminated body is grind | polished simultaneously. a method for manufacturing a substrate according to any one of 1-7.

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