JP2016212946A - Manufacturing method of substrate for magnetic disk and grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a substrate for a magnetic disk in which an end surface of the disc-shaped substrate is finished in high quality and stable grinding work becomes possible.SOLUTION: According to the present invention, a grinding fluid is brought into contact with an end surface portion of a disc-shaped substrate, and a grindstone is brought into contact with an outer circumferential side end surface and it is moved relatively to grind and machine a substrate end surface. The grindstone is formed in a cylindrical shape and has multiple groove shapes arranged in parallel in the inner circumferential side. The multiple groove shapes comprise grooves for coarse grinding work and grooves for precision grinding. The grindstone has means for preventing the grinding waste generated when performing the grinding work in the grooves for the coarse grinding work from moving to the grooves for precision grinding. Then, the outer circumferential side end surface of the substrate is sequentially brought into contact with the grooves for the coarse grinding work of the grindstone and the grooves for the precision grinding, and the outer circumferential side end surface of the substrate is ground and machined.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for manufacturing a magnetic disk substrate used for manufacturing a magnetic disk mounted on a magnetic recording apparatus such as a hard disk drive (hereinafter abbreviated as “HDD”), and end grinding of the magnetic disk substrate. The present invention relates to a grinding wheel for use in grinding.

  One of information recording media mounted on a magnetic recording device such as an HDD is a magnetic disk. A magnetic disk is configured by forming a thin film such as a magnetic layer on a disk-shaped substrate, and an aluminum alloy substrate or a glass substrate is used as the substrate. A glass substrate is harder than an aluminum alloy substrate, and has an advantage of excellent impact resistance. The surfaces of these substrates are polished and smoothed with high precision so as to reduce the flying height of the magnetic head as much as possible, thereby realizing high recording density. In recent years, the demand for further increase in recording capacity and price of HDDs has increased, and in order to realize this, it has become necessary to further improve the quality and cost of magnetic disk substrates. ing.

A magnetic disk substrate is usually manufactured by sequentially performing steps such as shape processing (end surface grinding and chamfering), end surface polishing, main surface grinding, main surface polishing, and chemical strengthening on a disk-shaped substrate.
As described above, there is a demand for a magnetic disk that is inexpensive and can achieve a high recording density. However, in order to increase the recording density of the magnetic disk, a high level of processing accuracy is required for the substrate. The same applies to the end surface shape as well as the main surface.

  As a conventional processing method of the end surface of the disk-shaped substrate, the grinding liquid is contacted and rotated on the outer peripheral side end surface and the inner peripheral side end surface of the substrate while bringing the grinding liquid into contact with the end surface portion of the substrate, and then the substrate is processed. A predetermined chamfering process was performed on the outer peripheral side end surface and the inner peripheral side end surface (Patent Document 1, etc.). In this case, the grindstone is generally called a general grindstone, and has a groove shape for forming the end face shape of the substrate. By processing the grindstone in contact with the end face of the substrate, The shape of the grindstone groove is transferred to the end face of the substrate. In addition, it is known that the grinding process is performed by being divided into a rough grinding process using a grinding wheel for rough grinding and a precision grinding process using a grinding wheel for precision grinding.

JP 2000-296470 A

  However, according to the study of the present inventor, conventionally, the outer peripheral side of the substrate is brought into contact with the rough grinding groove and the precision grinding groove formed on the inner peripheral side of the cylindrical grindstone by sequentially contacting the outer peripheral end surface of the substrate. When two-step processing of rough grinding and precision grinding is performed on the end face, chipping such as scratches may occur on the end face of the substrate after precision grinding.

  In view of the above, the first object of the present invention is to provide a method for manufacturing a magnetic disk substrate capable of finishing the end face of the disk-shaped magnetic disk substrate with high quality from the viewpoint of ensuring reliability. . It is a second object of the present invention to provide a grinding wheel that can be suitably used for end face grinding of the magnetic disk substrate.

  In order to solve the above-described conventional problems, the present inventor uses a grindstone that is formed in a cylindrical shape and has a plurality of parallel rough grinding and precision grinding grooves on its inner peripheral side. A method of grinding the outer peripheral side end surface of the substrate by bringing the outer peripheral side end surface of the disk-shaped substrate into contact with the inner peripheral side of the substrate and relatively moving the substrate and the grindstone (in this specification, for convenience of explanation) This processing method was called “inscribed grinding”, and the grindstone used therefor was sometimes called “inscribed grinding wheel” for convenience.)

As a result, the present inventors have found the following phenomenon.
As shown in FIG. 3, for example, the groove shape of the conventional inscribed grinding wheel includes a rough grinding region 2A including a plurality of grooves 2a, 2a, and a plurality of grooves 2b, 2b,. Including a precision grinding region 2B. The coarse grinding region 2A and the fine grinding region 2B have different abrasive grain sizes. First, rough grinding is performed in the coarse grinding region 2A of abrasive grains having a large abrasive grain size (coarse count abrasive grains). Thus, precision grinding (finish grinding) can be performed in the precision grinding region 2B of abrasive grains having a small abrasive grain size (fine count abrasive grains).

However, since the groove shape of the grindstone is inside the cylindrical shape in the inscribed grinding process, when grinding waste generated during grinding with the groove 2a for rough grinding is scattered around, precision grinding In some cases, it may reach the processing groove 2b (indicated by an arrow in FIG. 3). Many grinding scraps generated by rough grinding are relatively larger than those generated by precision grinding. Further, such grinding waste may be accumulated in the precision grinding groove 2b and become sludge. These foreign substances are likely to stick to the groove due to the centrifugal force generated by the rotation of the grindstone. As a result, the grinding scraps cause chipping and pit-like defects that occur during precision grinding, leading to deterioration of the end face quality. Thus, since the end surface quality of a glass substrate is deteriorated, the problem that a production yield also falls will arise.
As a result of further intensive studies, the inventor described above by providing means for suppressing the movement of grinding scrap generated when grinding is performed in the coarse grinding groove to the precision grinding groove. The present inventors have found that the above problem can be solved, and have completed the present invention.
That is, the present invention has the following configuration in order to solve the above problems.

(Configuration 1)
A magnetic disk substrate having a process of grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral side end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped substrate. The grindstone is formed in a cylindrical shape and has a plurality of parallel groove shapes on its inner peripheral side, and the plurality of groove shapes include a groove for rough grinding, and a precision A grinding groove, and has means for suppressing movement of grinding waste generated when grinding with the rough grinding groove to the precision grinding groove. An outer peripheral side end surface of the substrate is ground by bringing the outer peripheral side end surface of the substrate into contact with the rough grinding groove and the fine grinding groove in order. Production method.

(Configuration 2)
The means for suppressing the grinding scraps from moving to the precision grinding groove is a means for providing a wall between the rough grinding groove and the precision grinding groove. A method for manufacturing a magnetic disk substrate according to Configuration 1.

(Configuration 3)
The means for preventing the grinding scraps from moving into the precise grinding groove is provided with a step which becomes a wall between the rough grinding groove and the precision grinding groove to reduce the grindstone diameter. 3. The configuration 1 or 2, wherein the rough grinding groove is disposed on the larger grindstone diameter, and the precision grinding groove is disposed on the smaller grindstone diameter. A method of manufacturing a magnetic disk substrate.

(Configuration 4)
A magnetic disk substrate having a process of grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral side end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped substrate. The grindstone is formed in a cylindrical shape and has a plurality of parallel groove shapes on its inner peripheral side, and the plurality of groove shapes include a groove for rough grinding, and a precision A groove for grinding, and there is a raised portion between the groove for rough grinding and the groove for precision grinding, and the groove for rough grinding and the groove for precision grinding are sequentially formed. A method of manufacturing a magnetic disk substrate, comprising: grinding an outer peripheral side end surface of the substrate by bringing the outer peripheral side end surface of the substrate into contact with each other.

(Configuration 5)
A magnetic disk substrate having a process of grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral side end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped substrate. The grindstone is formed in a cylindrical shape and has a plurality of parallel groove shapes on its inner peripheral side, and the plurality of groove shapes include a groove for rough grinding, and a precision A plurality of regions having different diameters provided with steps on the inner peripheral side of the grindstone, and arranging the grooves for rough grinding in the region having a large diameter, The precision grinding groove is arranged on the smaller diameter side, and the outer peripheral side end face of the substrate is brought into contact with the rough grinding groove and the fine grinding groove in sequence with the outer peripheral side end face of the substrate. For magnetic disks characterized by grinding Method of manufacturing the plate.

(Configuration 6)
6. The method for manufacturing a magnetic disk substrate according to any one of Structures 1 to 5, wherein an electrodeposited grindstone is used as the grindstone.

(Configuration 7)
Grinding used for grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped magnetic disk substrate. The grinding wheel is formed in a cylindrical shape and has a plurality of parallel groove shapes on its inner peripheral side, and the plurality of groove shapes include a groove for rough grinding, A means for suppressing grinding dust generated when grinding is performed in the groove for rough grinding, to move to the groove for precision grinding. A grinding wheel characterized by comprising:

(Configuration 8)
Grinding used for grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped magnetic disk substrate. The grindstone is formed in a cylindrical shape and has a plurality of parallel groove shapes on the inner peripheral side thereof. The plurality of groove shapes include a groove for rough grinding and precision grinding. A grinding wheel characterized by comprising a groove for machining and having a raised portion between the groove for rough grinding and the groove for precision grinding.

(Configuration 9)
Grinding used for grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped magnetic disk substrate. The grindstone is formed in a cylindrical shape and has a plurality of parallel groove shapes on the inner peripheral side thereof. The plurality of groove shapes include a groove for rough grinding and precision grinding. A plurality of regions having different diameters provided with steps on the inner peripheral side of the grindstone, the grooves for rough grinding are disposed in the region having a large diameter, and the diameter A grinding wheel for grinding, characterized in that the groove for precision grinding is arranged on the smaller side.

  According to the method for manufacturing a magnetic disk substrate according to the present invention, the occurrence of chipping can be suppressed, and the end surface of the magnetic disk substrate can be finished with high quality. Furthermore, stable grinding can be performed. Here, by using the grinding wheel according to the present invention for the end face grinding of the substrate, the occurrence of chipping can be suppressed and the end face of the magnetic disk substrate can be finished with high quality.

It is sectional drawing which shows the end surface shape of a glass substrate. The embodiment of the end surface grinding process of the glass substrate in the present invention is shown, and is a sectional view on a plane including a circle formed by a groove shape of a grindstone. It is sectional drawing which shows an example (conventional example) of the groove shape of the grindstone used for the said end surface grinding process. It is sectional drawing which shows one Embodiment of the grindstone of this invention used for the said end surface grinding process. It is sectional drawing which shows other embodiment of the grindstone of this invention used for the said end surface grinding process. It is sectional drawing which shows other embodiment of the grindstone of this invention used for the said end surface grinding process. It is sectional drawing which shows other embodiment of the grindstone of this invention used for the said end surface grinding process.

Hereinafter, embodiments for carrying out the present invention will be described in detail. As described above, an aluminum alloy-based substrate also exists as a magnetic disk substrate. Here, a glass substrate will be described as an example. The aluminum alloy-based substrate can also be changed and applied as appropriate.
FIG. 1 is a cross-sectional view of the outer peripheral end of a magnetic disk glass substrate 1 to which the present invention is applied. Although the glass substrate 1 is not shown in FIG. 1, the whole having a circular hole in the center is formed in a disc shape (see FIG. 2), and main surfaces 1a and 1a on the front and back sides thereof, It has an outer peripheral end surface and an inner peripheral end surface formed between the surfaces 1a and 1a.

  The end surface on the outer peripheral side of the glass substrate 1 has a side wall surface 1b orthogonal to the main surface 1a, and two chamfered surfaces formed between the side wall surface 1b and the front and back main surfaces 1a and 1a ( A chamfered surface) 1c and 1c are formed. Moreover, although it does not show in figure about the end surface of the inner peripheral side of the said glass substrate 1, like the said outer peripheral side end surface, the side wall surface orthogonal to the main surface 1a, and this side wall surface and main surface 1a, 1a of the front and back Are formed in a shape composed of two chamfered surfaces formed respectively.

  The present invention can be preferably applied to a nominal 1.8 inch disk (outer diameter 48 mm) or more. For example, in the case of a nominal 2.5 inch disc, the glass substrate 1 is finished to have an outer diameter of 65 mm and an inner diameter of 20 mm. For example, in the case of a nominal 3.5 inch disk, the glass substrate 1 is finished to have an outer diameter of 95 mm and an inner diameter of 25 mm. Here, the inner diameter is the inner diameter of a circular hole in the center of the glass substrate 1. The plate thickness is about 0.6 to 1.5 mm in any size.

  The main surface 1a, the outer peripheral side end surface, and the inner peripheral side end surface of the glass substrate 1 for magnetic disk are all polished (mirror polished) so as to finally have a predetermined surface roughness. Both the outer peripheral side end face and the inner peripheral side end face of the glass substrate 1 are finished in the end face shape as described above, and the surface roughness is finished in a mirror surface state with Rmax of 1 μm or less and Ra of 0.1 μm or less, for example. It is usually sought to be.

The magnetic disk glass substrate 1 is formed by subjecting a glass plate 1 obtained by processing, for example, a glass plate obtained by a direct press method or a float method into a predetermined disc shape, and grinding and polishing an end face ( (Mirror polishing), grinding of the main surface, mirror polishing, chemical strengthening, etc. are performed in order.
In the present specification, a glass substrate (glass base plate) obtained by processing a glass plate obtained by a direct press method or a float method into a predetermined disc shape is processed, processed, etc. For the sake of convenience of explanation, all the steps up to the glass substrate of the final product to be manufactured are referred to as a glass substrate or a magnetic disk glass substrate.
First, the grinding / polishing process of the end face of the glass substrate 1 will be described.

In the method for manufacturing a glass substrate for a magnetic disk according to the present invention, a grinding stone is brought into contact with the outer peripheral side end surface of the substrate while bringing the grinding liquid into contact with the end surface portion of the disk-shaped substrate as in the above-described configuration 1. A method of manufacturing a magnetic disk substrate having a process of grinding an end face of the substrate by relatively moving the grindstone, wherein the grindstone is formed in a cylindrical shape and is arranged in parallel on the inner peripheral side thereof A plurality of groove shapes, each of which includes a rough grinding groove and a precision grinding groove, and is generated when grinding is performed with the rough grinding groove. Means for suppressing movement of scraps into the precision grinding groove is provided, and the outer peripheral side end surface of the substrate is sequentially brought into contact with the rough grinding groove and the precision grinding groove. To grind the outer peripheral side end surface of the substrate. It has a configuration.
The end surface grinding performed in the present invention is an inscribed grinding process. Moreover, the grindstone used for the end surface grinding of the present invention is an inscribed grinding grindstone. Hereinafter, the end face grinding of the present invention will be described in detail.

  In the end surface grinding process performed in the present invention, the outer peripheral side end surface of the glass substrate is brought into contact with the inner peripheral side of the grindstone formed in a cylindrical shape, and the glass substrate and the grindstone are relatively moved, whereby the outer periphery of the glass substrate. It is the structure which grinds a side end surface. For example, specifically, as shown in FIG. 2, the grindstone (rotary grindstone) 3 for processing the substrate outer peripheral side is in the direction of the arrow 13 (cutting direction) in the figure with respect to the outer peripheral side end surface of the glass substrate 1. Contact. Moreover, you may make it contact the glass substrate 1 with respect to the said grindstone in the arrow 12 direction (cutting direction) in a figure.

  The grindstone 3 is formed in a cylindrical shape and has a plurality of parallel groove shapes for forming the end face shape of the glass substrate on the inner peripheral surface thereof. The groove shape is such that both the side wall surface and the chamfered surface can be transferred to the outer peripheral side end surface. That is, the grindstone 3 is formed in a predetermined dimensional shape in consideration of a target dimensional shape of the ground surface of the glass substrate 1.

  In this case, it is preferable to perform the processing while rotating the grindstone 3 and the glass substrate 1, and the peripheral speed and the peripheral speed ratio may be appropriately set so as to be suitable for processing of the outer peripheral side end face. In FIG. 2, the glass substrate 1 is rotated in the direction of arrow 10 and the grindstone 3 is rotated in the direction of arrow 11, but the rotation direction is not particularly limited. The rotation direction of the grindstone 3 and the glass substrate 1 may be either the same direction (down cut) or a different direction (up cut) at the processing position (contact position).

From the viewpoint of grindability and processing efficiency, for example, the peripheral speed of the grindstone 3 is preferably 300 to 3000 m / min, and the peripheral speed at the processing position of the glass substrate 1 is preferably about 3 to 100 m / min.
Moreover, about the grinding fluid (coolant) used for such a grinding process, the cooling effect is high and the water-soluble grinding fluid with high safety | security at a production site is suitable.

Incidentally, the grindstone 3 has a cross-sectional shape as shown in FIG. FIG. 4 is a cross-sectional view showing an embodiment of the grindstone of the present invention used in the end face machining step.
That is, the grindstone 3 is formed in a cylindrical shape as a whole and has a plurality of parallel groove shapes on the inner peripheral side thereof. The plurality of groove shapes include a groove for rough grinding and a precision grinding process. And a groove for use. Specifically, as shown in FIG. 4, a rough grinding region 3A and a precision grinding (finish grinding) region 3B are provided, and the rough grinding region 3A includes a plurality of grooves 3a, 3a,. .. And the precision grinding region 3B has a plurality of grooves 3b, 3b. Each of the plurality of groove shapes of the grindstone 3 may be formed so that both the side wall surface and the chamfered surface of the outer peripheral side end surface of the glass substrate 1 can be ground simultaneously.

The coarse grinding region 3A and the fine grinding region 3B have different abrasive grain sizes. First, rough grinding is performed in the coarse grinding region 3A of abrasive grains having a large abrasive grain size (coarse count abrasive grains). Thus, precision grinding (finish grinding) can be performed in the precision grinding region 3B of the abrasive grains having a small abrasive grain size (fine count abrasive grains).
The grindstone 3 according to the present invention has means for suppressing the grinding waste generated when grinding is performed in the rough grinding groove 3a from moving to the precision grinding groove 3b. ing.

  Specifically, as can be seen with reference to FIG. 4, the present embodiment includes a rough grinding region 3A including a plurality of grooves 3a for rough grinding and a plurality of grooves 3b for precision grinding. A step 31 serving as a wall is provided between the precision grinding region 3B and the diameter of the grindstone is made different. Therefore, the rough grinding groove 3a is disposed in the region having the larger grindstone diameter, and the precision grinding groove 3b is disposed in the region having the smaller grindstone diameter. According to such a configuration, even if grinding waste generated when grinding is performed in the rough grinding groove 3a, the rough grinding region 3A and the precision grinding region 3B Since the step 31 serving as a wall is provided between them, even if the grinding waste generated in the rough grinding groove 3a is scattered, the step 31 prevents the grinding scraps from reaching the groove 3b for precision grinding. Can be suppressed. As described above, in the present embodiment, in order to suppress movement of grinding waste generated when grinding is performed in the rough grinding groove 3a to the precision grinding groove 3b, a conventional configuration is used. As shown in FIG. 3, in the precision grinding, it is possible to effectively reduce the occurrence of chipping due to the influence of the coarse grinding sludge accumulated in the precision grinding groove 2b.

In the embodiment of FIG. 4, the grinding wheel diameter (hereinafter referred to as “the diameter of the precision grinding wheel”) of the precision grinding region 3 </ b> B including the plurality of grooves 3 b for precision grinding is preferably as follows. .
That is, when the diameter of the glass substrate 1 to be processed is L (mm), the diameter of the precision grinding wheel is preferably L + 1 (mm) or more and 300 mm or less. More preferably, it is L + 5 (mm) or more and 2 L (mm) or less.

  If the diameter of the precision grinding wheel is smaller than L + 1 (mm), the grinding wheel wears quickly, and the productivity may deteriorate. On the other hand, if the diameter of the precision grinding wheel is larger than 300 mm, the size of the grinding wheel becomes large and the cost may increase. Moreover, it may be difficult to move the grindstone with high accuracy.

  The diameter of the grindstone here refers to the diameter at the position of the groove bottom surface of the grindstone. Further, the groove bottom surface of the grindstone is the deepest bottom surface of the groove, and is usually a processing surface for grinding the side wall surface of the substrate end surface. In the following, the same meaning is used.

In the embodiment of FIG. 4, the grinding wheel diameter (hereinafter referred to as “rough grinding wheel diameter”) of the rough grinding region 3 </ b> A including the plurality of rough grinding grooves 3 a and the diameter of the precision grinding wheel are as follows. The difference is preferably as follows.
The value obtained by subtracting the diameter of the precision grinding wheel from the diameter of the rough grinding wheel, that is, the difference between the diameter of the coarse grinding wheel and the diameter of the precision grinding wheel is preferably 0.4 mm or more and 60 mm or less. More preferably, it is 4 mm or more and 20 mm or less.

  If the difference between the diameter of the coarse grinding wheel and the diameter of the precision grinding wheel is less than 0.4 mm, the grinding dust generated when grinding with the coarse grinding groove will become a precision grinding groove. The effect of suppressing movement cannot be sufficiently obtained. On the other hand, if the difference between the diameter of the coarse grinding wheel and the diameter of the precision grinding wheel is larger than 60 mm, the processing becomes difficult and the cost increases, and the moving distance of the glass substrate to be processed increases, so that the productivity may deteriorate. There is sex.

  In addition, the grinding scraps generated in the precision grinding process do not affect the generation of defects in the precision grinding. That is, when the size of the grinding waste depending on the abrasive grain size in a certain grinding process is larger than the size of the grinding waste generated by the grinding, a defect is generated in the glass substrate. In short, the problem is that grinding scrap generated by rough grinding accumulates in the grooves for precision grinding, which causes defects such as chipping on the glass substrate by precision grinding.

Examples of the grindstone 3 used in the inscribed end face grinding of the present invention include, for example, a so-called electrodeposition grindstone obtained by electrodeposition of diamond, Al ₂ O ₃ , SiC, CBN or the like, which is a high-rigidity material, or composite abrasive grains thereof. A so-called metal grindstone in which abrasive grains are hardened with a metallic binder is suitable. In particular, when an electrodeposited grindstone is used, the abrasive grain layer can be made relatively thin with respect to the base metal, so that the groove-shaped transfer shape can be maintained relatively accurately over the entire usable period of the grindstone. In addition, when a metal grindstone is used, the grinding action is performed by the abrasive grains protruding from the metallic bond layer, which is preferable because the roughness is suppressed. As the particle size of the abrasive grains, for example, # 200 to # 800 are suitable for rough grinding, and for example, # 800 to # 4000 are suitable for precision grinding.

  Further, as another embodiment of the grindstone of the present invention used in the end face machining step, as shown in FIG. 5, a coarse grinding region 4A including a plurality of coarse grinding grooves 4a, and a precision grinding work A raised portion 41 serving as a wall is provided between the fine grinding region 4B including the plurality of grooves 4b.

In the embodiment of FIG. 5, the height of the raised portion 41 is preferably 0.2 mm or more and 30 mm or less. More preferably, it is 2 mm or more and 10 mm or less.
In addition, the height of the raised part said here shall say the length from the lower end (position of the grindstone surface in a place without a groove | channel) to a front-end | tip (apex) of a raised part. In the following, the same meaning is used.
When the height of the raised portion 41 is smaller than 0.2 mm, it is possible to prevent the grinding dust generated when grinding is performed in the rough grinding groove from moving to the precision grinding groove. The effect cannot be obtained sufficiently. On the other hand, when the height of the raised portion 41 is larger than 30 mm, processing is difficult and cost is increased, and the moving distance of the glass substrate to be processed is increased, so that productivity may be deteriorated.

  In the present embodiment, even if grinding waste generated when grinding is performed in the coarse grinding groove 4a is scattered toward the precision grinding region 4B, the coarse grinding region 4A and the precision grinding are performed. Since it is blocked by the raised portion 41 provided between the processing region 4B and the grinding scrap generated in the rough grinding groove 4a, it is prevented from reaching and accumulating in the precision grinding groove 4b. Can do.

Further, as another embodiment of the grindstone of the present invention used in the end face machining step, as shown in FIG. 6, a rough grinding region 5A including a plurality of grooves 5a for rough grinding, A step 51 is provided between the precision grinding region 5B including the plurality of grooves 5b, and the grindstone diameter is different from that in the embodiment shown in FIG.
In the present embodiment, even if grinding scraps generated during grinding with the coarse grinding groove 5a are scattered toward the precision grinding region 5B, the coarse grinding region 5A and the precision grinding are performed. Since it is obstructed by the step 51 between the processing region 5B, it is possible to suppress the grinding waste generated in the rough grinding groove 5a from reaching and accumulating in the precision grinding groove 5b.

Further, as another embodiment of the grindstone of the present invention, as shown in FIG. 7, a rough grinding region 6A including a plurality of grooves 6a for rough grinding and a plurality of grooves 6b for precision grinding are included. A step 61 having a cross-sectional shape as shown in the figure is provided between the precision grinding region 6B and the grindstone diameter is different from that in the embodiment shown in FIG.
Also in the present embodiment, even if grinding waste generated when grinding is performed in the groove 6a for rough grinding is scattered by the above-described step 61 even if it is scattered toward the precision grinding region 6B, rough grinding is performed. It is possible to suppress grinding waste generated in the grinding groove 6a from reaching and accumulating in the precision grinding groove 6b.

  In the above-described embodiments shown in FIGS. 4, 6, and 7, there is a case where there is a single step, and there are regions having different two-stage grindstone diameters as a whole. However, the present invention includes an embodiment in which a plurality of steps are provided in a plurality of steps and there are a plurality of regions having different grindstone diameters. In this case, among the plurality of regions having different grinding wheel diameters, the rough grinding groove is disposed in a region having a larger grinding wheel diameter, and the precise grinding groove is disposed in a region having a smaller grinding wheel diameter. . For example, in the case where there are regions with different three-stage grindstone diameters as a whole, the coarse grinding groove is disposed in the region having the largest grindstone diameter, and the precision grinding groove is disposed in the region having the smallest grindstone diameter. In the region of the intermediate grindstone diameter, for example, a groove for processing in the second stage of rough grinding is arranged.

In the above-described end face grinding in the present invention, the grinding may be performed while rotating both of the glass substrates while the rotation axis of the glass substrate is inclined with respect to the rotation axis of the cylindrical grinding wheel. As a result, the trajectory of the grindstone that comes into contact with the end surface of the glass substrate 1 does not become constant, and the convex portions (abrasive grains) of the grindstone come into contact with and act at random positions on the end surface of the substrate. Therefore, the surface roughness and in-plane variation of the ground surface can be reduced, and the ground surface can be finished with higher smoothness.
In addition to the above-described end face grinding of the present invention, a conventional brush polishing process or the like may be performed as necessary.

The glass type used for the magnetic disk glass substrate is not particularly limited. Examples of the glass substrate material include aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, Examples thereof include glass ceramics such as quartz glass, chain silicate glass, or crystallized glass. Of these, aluminosilicate glass is particularly preferable because it is excellent in impact resistance and vibration resistance.
The glass substrate that has been subjected to the grinding and polishing steps of the outer peripheral side and inner peripheral side end surfaces of the substrate as described above is then subjected to a mirror polishing step, a chemical strengthening step, and the like of the main surface, as shown in FIG. Such a magnetic disk glass substrate 1 is obtained.

  As described above, the case of the glass substrate as an example of the magnetic disk substrate has been described. However, as described above, an aluminum alloy-based substrate also exists as the magnetic disk substrate, and the above-described surface grinding process of this aluminum alloy-based substrate also includes The end surface grinding process of the present invention can be preferably applied, and the processing quality of the substrate end surface can be improved. The aluminum alloy substrate includes an aluminum alloy substrate and an aluminum alloy substrate having a NiP alloy formed on the surface thereof.

The present invention also provides a magnetic disk manufacturing method in which at least a magnetic layer is formed on the main surface of the magnetic disk glass substrate manufactured by the above-described method for manufacturing a magnetic disk glass substrate according to the present invention.
That is, for example, a magnetic disk can be obtained by forming at least a magnetic layer on a glass substrate for a magnetic disk obtained by the above-described embodiment of the present invention. Usually, for example, a magnetic disk in which an adhesion layer, a soft magnetic layer, an underlayer, a magnetic layer, a protective layer, a lubricating layer, and the like are provided on a glass substrate is preferable.

For example, the magnetic layer may be, for example, an alloy having a Co-based hcp crystal structure for a perpendicular magnetic recording medium.
Moreover, as a protective layer, a carbon-type protective layer etc. are mentioned preferably, for example. Examples of the lubricant that forms the lubricating layer on the protective layer include PFPE (perfluoropolyether) compounds.
As a method for forming each of the layers on the glass substrate, a known sputtering method or the like can be used. A plasma CVD method is also preferably used for forming the carbon-based protective layer. A dipping method or the like can be used for forming the lubricating layer.

  By manufacturing a magnetic disk using the glass substrate for magnetic disk manufactured by the method for manufacturing a glass substrate for magnetic disk according to the present invention, the end surface of the substrate can be finished with high quality, and the surface state of the substrate end surface is caused. Therefore, it is possible to provide a magnetic disk capable of preventing the occurrence of the failure and realizing higher recording density and higher reliability.

Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.
Example 1
First, a glass substrate (glass base plate) made of a disc-shaped aluminosilicate glass having a diameter of 66 mmφ and a plate thickness of 0.9 mm was obtained from molten glass by a direct press method.

  Next, a lapping process was performed on the glass substrate in order to improve dimensional accuracy and shape accuracy. This lapping process was performed using a double-sided lapping apparatus.

Next, a hole was made in the central portion of the glass substrate using a cylindrical grindstone. Next, the outer peripheral end face of the substrate was ground.
As the grindstone used, an electrodeposition grindstone having a diameter difference as shown in FIG. 4 was selected. The diameter of the precision grinding wheel was 110 mm, and the diameter of the rough grinding wheel was 116 mm. The definition of the diameter of the grindstone is as described above. The depth of the grindstone groove is 0.5 mm, the width of the groove bottom is 0.5 mm, and the opening angle of the groove is 45 degrees. The groove shape can be either a rough grinding region or a precision grinding region. The same is true. The size (count) of the abrasive grains for rough grinding is # 500, and the size (count) of the abrasive grains for precision grinding is # 1000.
Grinding is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 2, and the peripheral speed, rotation direction, and cutting speed of each of the glass substrate and the grindstone can be appropriately set. The rotation speed of the glass substrate was 200 rpm, the rotation speed of the grindstone was 6000 rpm, and the rotation direction of the glass substrate and the grindstone was reversed.

As described above, end face processing of 100 glass substrates was performed.
With respect to the obtained 100 glass substrates, the presence or absence of occurrence of chipping at the corner portion A formed by the side wall surface and the chamfered surface and the corner portion B formed by the main surface and the chamfered surface (see FIG. 1) was visually observed. It was investigated by microscopic observation.

(Example 2)
Grinding was performed in the same manner as in Example 1 except that the electrodeposition grindstone having a cross-sectional shape as shown in FIG. 5 was used.
Both the diameter of the precision grinding wheel and the diameter of the rough grinding wheel were 110 mm, and the height of the raised portion was 3 mm. The definition of the height of the raised portion is as described above. The depth of the grindstone groove is 0.5 mm, the width of the groove bottom is 0.5 mm, and the opening angle of the groove is 45 degrees. The groove shape can be either a rough grinding region or a precision grinding region. The same is true.
End face processing of 100 glass substrates is performed, and the corner portion A formed by the side wall surface and the chamfered surface and the main surface and the chamfered surface are formed on the 100 glass substrates obtained in the same manner as in Example 1. The presence or absence of chipping at the corner B (see FIG. 1) was examined by visual observation and microscopic observation.

(Comparative example)
Further, as a comparative example, grinding was performed in the same manner as in Example 1 except that an electrodeposited grinding stone having a cross-sectional shape as shown in FIG. 3 was used.
Both the diameter of the precision grinding wheel and the diameter of the rough grinding wheel were 110 mm. The depth of the grindstone groove is 0.5 mm, the width of the groove bottom is 0.5 mm, and the opening angle of the groove is 45 degrees. The groove shape can be either a rough grinding region or a precision grinding region. The same is true.
End face processing of 100 glass substrates is performed, and the corner portion A formed by the side wall surface and the chamfered surface and the main surface and the chamfered surface are formed on the 100 glass substrates obtained in the same manner as in Example 1. The presence or absence of chipping at the corner B (see FIG. 1) was examined by visual observation and microscopic observation.

As a result, the chipping rates in Example 1 and Example 2 were both 3% or less, whereas in the comparative example, they were very high at 60%. In particular, chipping occurred frequently after the 20th sheet.
In addition, when the grindstone after the processing was finished, the grooves for precision grinding were observed in detail. In the grindstone used in Example 1 and Example 2, almost no sludge was found, but this was used in the comparative example. In the grindstone, sludge accumulation was observed.

As is apparent from this result, according to the present invention, there is provided means for suppressing the movement of the grinding scrap generated when grinding is performed in the rough grinding groove to the precision grinding groove. Since a grinding wheel was used, the occurrence of chipping could be suppressed and grinding with good finished surface quality could be performed.
On the other hand, in the processing using the conventional inscribed grinding wheel, since sludge of grinding scraps in coarse grinding accumulates in the grooves for precision grinding, the occurrence rate of chipping is high, and the yield is significantly reduced.
In Example 2 described above, there is a possibility that the flow of the grinding fluid may be hindered by the raised portion of the grindstone, and there is a possibility that the supply method of the grinding fluid may be complicated in order to sufficiently distribute the grinding fluid to the processing surface. is there. On the other hand, in the first embodiment, since the grinding fluid is supplied from the precision grinding wheel side, the grinding fluid is sufficiently supplied to the rough grinding stone side, and the supply method is not complicated, which is more preferable. .

DESCRIPTION OF SYMBOLS 1 Glass substrate 2-6 for magnetic discs Peripheral end face grinding grindstone 1a Main surface 1b of glass substrate Side wall surface 1c Chamfered surface 31 Step 41 Raised part (wall)

Claims (9)

A magnetic disk substrate having a process of grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral side end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped substrate. A manufacturing method of
The grindstone is formed in a cylindrical shape and has a plurality of groove shapes on the inner peripheral side thereof, and the plurality of groove shapes include a groove for rough grinding and a groove for precision grinding, It has means for suppressing grinding scraps generated when grinding with the rough grinding groove from moving to the precision grinding groove,
Manufacturing of a substrate for a magnetic disk, wherein the outer peripheral side end surface of the substrate is ground by sequentially bringing the outer peripheral side end surface into contact with the rough grinding groove and the precision grinding groove. Method.   The means for suppressing the grinding scraps from moving to the precision grinding groove is a means for providing a wall between the rough grinding groove and the precision grinding groove. A method for manufacturing a magnetic disk substrate according to claim 1.   The means for preventing the grinding scraps from moving into the precise grinding groove is provided with a step which becomes a wall between the rough grinding groove and the precision grinding groove to reduce the grindstone diameter. 3. The means according to claim 1 or 2, wherein the rough grinding groove is disposed on the larger grindstone diameter, and the fine grinding groove is disposed on the smaller grindstone diameter. Of manufacturing a magnetic disk substrate. A magnetic disk substrate having a process of grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral side end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped substrate. A manufacturing method of
The grindstone is formed in a cylindrical shape and has a plurality of groove shapes on the inner peripheral side thereof, and the plurality of groove shapes include a groove for rough grinding and a groove for precision grinding, There is a raised portion between the rough grinding groove and the precision grinding groove,
Manufacturing of a substrate for a magnetic disk, wherein the outer peripheral side end surface of the substrate is ground by sequentially bringing the outer peripheral side end surface into contact with the rough grinding groove and the precision grinding groove. Method. A magnetic disk substrate having a process of grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral side end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped substrate. A manufacturing method of
The grindstone is formed in a cylindrical shape and has a plurality of groove shapes on the inner peripheral side thereof, and the plurality of groove shapes include a groove for rough grinding and a groove for precision grinding,
Steps are provided on the inner peripheral side of the grindstone, and there are a plurality of regions having different diameters. The grooves for rough grinding are arranged in the regions having a large diameter, and the fine grinding is used in the region having the smaller diameter. Place the groove of
Manufacturing of a substrate for a magnetic disk, wherein the outer peripheral side end surface of the substrate is ground by sequentially bringing the outer peripheral side end surface into contact with the rough grinding groove and the precision grinding groove. Method.   6. The method for manufacturing a magnetic disk substrate according to claim 1, wherein an electrodeposition grindstone is used as the grindstone. Grinding used for grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped magnetic disk substrate. A grinding wheel for
The grinding wheel is formed in a cylindrical shape and has a plurality of groove shapes on its inner peripheral side. The plurality of groove shapes include a groove for rough grinding and a groove for precision grinding. Including a means for suppressing movement of grinding waste generated when grinding is performed in the coarse grinding groove to the precision grinding groove. Whetstone. Grinding used for grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped magnetic disk substrate. A grinding wheel for
The grindstone is formed in a cylindrical shape and has a plurality of groove shapes on the inner peripheral side thereof, and the plurality of groove shapes include a groove for rough grinding and a groove for precision grinding, A grinding wheel having a raised portion between the rough grinding groove and the precision grinding groove. Grinding used for grinding the end surface of the substrate by bringing a grinding stone into contact with the outer peripheral end surface of the substrate and moving it relatively while contacting the end surface portion of the disk-shaped magnetic disk substrate. A grinding wheel for
The grindstone is formed in a cylindrical shape and has a plurality of groove shapes on the inner peripheral side thereof, and the plurality of groove shapes include a groove for rough grinding and a groove for precision grinding,
Steps are provided on the inner peripheral side of the grindstone, and there are a plurality of regions having different diameters. The grooves for rough grinding are arranged in the regions having a large diameter, and the fine grinding is used in the region having the smaller diameter. A grindstone for grinding, characterized in that a groove is arranged.

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