WO2014178416A1 - Grinding stone, method for manufacturing glass substrate for magnetic disc, and magnetic disc manufacturing method - Google Patents
Grinding stone, method for manufacturing glass substrate for magnetic disc, and magnetic disc manufacturing method Download PDFInfo
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- WO2014178416A1 WO2014178416A1 PCT/JP2014/062030 JP2014062030W WO2014178416A1 WO 2014178416 A1 WO2014178416 A1 WO 2014178416A1 JP 2014062030 W JP2014062030 W JP 2014062030W WO 2014178416 A1 WO2014178416 A1 WO 2014178416A1
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- glass substrate
- grinding
- grinding wheel
- grindstone
- magnetic disk
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
- G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B9/00—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor
- B24B9/02—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground
- B24B9/06—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain
- B24B9/065—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain of thin, brittle parts, e.g. semiconductors, wafers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
- B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
- B24D5/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting only by their periphery; Bushings or mountings therefor
Definitions
- the present invention relates to a grinding wheel used for end face grinding in manufacturing a glass substrate for a magnetic disk mounted on a magnetic recording device such as a hard disk drive (hereinafter abbreviated as “HDD”), and a substrate using the grinding wheel.
- the present invention relates to a method for manufacturing a glass substrate for a magnetic disk for performing end face grinding, and a method for manufacturing a magnetic disk using the glass substrate according to this manufacturing method.
- a magnetic disk which is a recording medium mounted on a magnetic recording device such as an HDD
- a technique capable of realizing an information recording density of 750 GB or more per magnetic disk is required due to a demand for a high capacity.
- an information recording medium substrate such as a magnetic disk
- an aluminum-based alloy substrate has been widely used as an information recording medium substrate such as a magnetic disk.
- a ratio of a glass substrate as a magnetic disk substrate suitable for high recording density has been increased. It's getting higher. Since the glass substrate has higher rigidity than the aluminum-based alloy substrate, it is suitable for high-speed rotation of the magnetic disk device, and a smooth surface can be obtained, so that it is easy to reduce the flying height of the magnetic head, and recording This is preferable because the S / N ratio of the signal can be improved.
- a glass substrate for a magnetic disk is usually manufactured by subjecting a glass base plate formed into a disk shape to steps such as end face grinding / polishing, main surface grinding / polishing, and chemical strengthening sequentially.
- a grinding stone is applied to the outer peripheral side end surface and the inner peripheral side end surface of the glass substrate while supplying the grinding liquid to the end surface portion of the glass base plate (glass substrate) formed into a disk shape. Grinding was performed by rotating the contact, and predetermined chamfering was performed on the outer peripheral side end surface and the inner peripheral side end surface of the glass substrate (Patent Document 1, etc.).
- the grindstone is generally called a general grindstone, and has a groove shape for forming the end face shape of the glass substrate. The grindstone is processed by contacting with the end face of the glass substrate. Thus, the shape of the groove of the grindstone is transferred to the end surface of the glass substrate. Further, after this chamfering process, brush polishing has been performed in order to process the end surface of the glass substrate into a mirror surface.
- substrate end face grinding is performed first by rough grinding to form the end face shape, such as chamfering, and then, in addition to ensuring the end face shape and dimensional accuracy, the surface roughness quality is ensured.
- Precision grinding finish grinding
- a hard electrodeposition bond grindstone is often used.
- the hardness of a grinding wheel As for the hardness of a grinding wheel, methods such as a hardness test using an Ogoshi type tester and a hardness evaluation using a Rockwell hardness meter have been known. However, according to the study of the present inventors, the hardness of the grinding wheel evaluated by these methods and the grinding performance (grinding speed, grinding surface roughness, shape when the substrate end face grinding is actually performed using this grinding wheel) There was no clear correlation with the dimensional accuracy, etc., and it turned out that the quality of the grinding wheel could not be judged without actually using it.
- the said patent document 2 finishes finishing the roughness Ra of a processed surface to 100 nm or less by using the resin bond grindstone which used urethane resin, urea resin, etc. as a binder (binder) to a diamond abrasive grain.
- the constituent material of the grindstone component is shown, and there is no disclosure of the specific grindstone specifications, particularly the hardness index of the grindstone that affects the grinding performance. Even if the constituent materials of the grindstone are the same, if the hardness is different, there will be a difference in the grinding speed and the quality of the machined surface, and it is difficult to obtain a stable quality in mass production.
- the quality requirements for the glass substrate for magnetic disks such as the dimensional shape accuracy of the end surface of the glass substrate and the finished surface quality of the chamfering process, are increasing more than ever before.
- a first object is to provide a grinding wheel capable of obtaining stable quality.
- a second object of the present invention is to provide a method for manufacturing a glass substrate for a magnetic disk, which can perform stable end surface grinding in mass production using this grinding wheel.
- it is a third object to provide a method of manufacturing a magnetic disk using a glass substrate by such a manufacturing method.
- the present invention has the following configuration in order to solve the above problems.
- (Configuration 1) A grinding wheel for precisely grinding an end face of a disk-shaped glass substrate having a circular hole in the center, wherein the grinding wheel includes abrasive grains and a binder for bonding the abrasive grains, and the grinding wheel A grinding wheel characterized in that the hardness of the binder part on the surface measured by the nanoindentation test method under the condition of indentation load of 250 mN using a Berkovich indenter is in the range of 0.4 to 1.7 GPa .
- a method for producing a glass substrate for a magnetic disk including a grinding process for precisely grinding an end face of a disk-shaped glass substrate having a circular hole in the center using a grinding wheel, the grinding wheel comprising abrasive grains and the abrasive grains And a binder part on the surface of the grinding wheel using a Barkovic indenter, a hardness measured by a nanoindentation test method under a pressing load condition of 250 mN, and using this grinding wheel, The correlation with the grinding speed when the glass substrate end face is ground under certain conditions is obtained in advance, and based on the obtained correlation, a grinding wheel having a hardness that provides a desired grinding speed is selected.
- a method for producing a glass substrate for a magnetic disk wherein the grinding process is performed using a selected grinding wheel.
- (Configuration 8) The method for producing a glass substrate for a magnetic disk according to any one of the constitutions 4 to 7, wherein the grinding treatment is performed so that the surface roughness Ra of the end face of the glass substrate is 0.1 ⁇ m or less.
- (Configuration 9) A magnetic disk manufacturing method comprising: forming at least a magnetic layer on a main surface of a magnetic disk glass substrate manufactured by the magnetic disk glass substrate manufacturing method according to any one of Structures 4 to 8.
- the end surface of the magnetic disk glass substrate can be efficiently finished with high quality, and stable quality can be obtained even in mass production processing. Therefore, it is possible to meet the demand for higher recording density of the magnetic disk, which is urgently required to ensure reliability. Further, according to the method for manufacturing a glass substrate for magnetic disk according to the present invention, it is possible to perform end surface grinding with stable quality even in mass production using this grinding wheel, and as a result, glass for magnetic disk is obtained. The end face of the substrate can be finished with high quality.
- the end surface of the substrate can be finished with high quality, and the surface state and processing of the substrate end surface It is possible to provide a highly reliable magnetic disk capable of preventing a failure due to accuracy and realizing a higher recording density.
- An embodiment of an end surface grinding method is shown, (a) is a perspective view, (b) is a front view in which the orientation is changed from (a).
- the other embodiment of an end surface grinding method is shown, (a) is a perspective view, (b) is the front view which changed direction from (a).
- FIG. 4 is a cross-sectional view of the outer peripheral end of the magnetic disk glass substrate 1 to which the present invention is applied.
- the glass substrate 1 is not shown in FIG. 4, the whole having a circular hole 4 in the center is formed in a disc shape (see FIG. 1 and the like), and main surfaces 1a and 1a on the front and back sides thereof, and these It has an outer peripheral end face and an inner peripheral end face formed between the main surfaces 1a and 1a.
- the outer peripheral end surface of the glass substrate 1 has a side wall surface 1b orthogonal to the main surface 1a, and two chamfered surfaces (chamfered surfaces) formed between the side wall surface 1b and the front and back main surfaces 1a and 1a.
- the glass substrate 1 is finished to have an outer diameter of 65 mm and an inner diameter of 20 mm.
- the inner diameter is the inner diameter of a circular hole in the center of the glass substrate 1.
- 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 surface and the inner peripheral side end surface of the glass substrate 1 are finished to the end surface shape as described above, and the surface roughness is, for example, Rmax of 0.1 ⁇ m or less and Ra of 0.01 ⁇ m or less. It is usually required to be finished.
- Ra and Rmax are arithmetic average roughness and maximum roughness according to Japanese Industrial Standard (JIS) B0601: 1982.
- the surface roughness of the end face is a value measured in a measurement region of 50 ⁇ m ⁇ 50 ⁇ m using a laser microscope with an observation magnification of 3000 times.
- the glass substrate 1 for a magnetic disk is usually subjected to grinding / polishing (mirror polishing) of the end surface, grinding / mirror polishing of the main surface, chemical treatment on a glass substrate (glass disk) 1 formed into a predetermined disk shape by, for example, direct pressing. Manufactured with sequential steps such as strengthening. First, the grinding / polishing process of the end face of the glass substrate 1 will be described. In the present specification, for convenience of explanation, from a glass disk molded into a predetermined disk shape by direct press or the like to a final product glass substrate produced by processing, processing, etc. on this glass disk. These are all referred to as glass substrates or magnetic disk glass substrates.
- FIG. 1A and 1B show an embodiment of the end face grinding method, wherein FIG. 1A is a perspective view and FIG. 1B is a front view in which the direction is changed from FIG.
- a drilling process is performed at the center, and the glass substrate 1 having the circular holes 4 is processed using the grindstone 7 for the outer peripheral end face and the grindstone 8 for the inner peripheral end face.
- the grindstone 7 is formed in a disk shape of a predetermined size as shown in the figure, and has a groove shape for forming the end face shape of the glass substrate on the outer peripheral side thereof.
- the groove shape is such that both the side wall surface and the chamfered surface can be transferred onto the outer peripheral side end surface of the glass substrate.
- the grindstone 8 is formed in a columnar shape having a predetermined size as shown in the figure, and has a groove shape for forming the end face shape of the glass substrate on the outer peripheral side thereof. Has a groove shape that allows shape transfer of both the side wall surface and the chamfered surface to the inner peripheral side end surface of the glass substrate. That is, the grindstone 7 and the grindstone 8 are both formed in a predetermined dimensional shape in consideration of the target dimensional shape of the ground surface of the glass substrate 1.
- a so-called electrodeposited bond grindstone in which diamond abrasive grains, which are high-rigidity grindstones are hardened with an electrodeposition bond, is suitable for rough grinding.
- a resin bond grindstone in which the binder for bonding abrasive grains is a resin material such as phenol resin, urethane resin, polyimide resin, polyester resin, fluororesin, or the binder is copper-based, for example.
- a metal bond grindstone that is a metallic binder such as an alloy, cast iron alloy, or titanium alloy, and a vitrified grindstone whose binder is a vitreous binder are suitable.
- a resin bond grindstone in which the adjustment of the hardness of the grindstone is relatively easy is particularly suitable.
- the grain size of the abrasive grains for example, abrasive grains having an average grain diameter of 30 ⁇ m or less are suitable in order to maintain the grinding performance over the entire grinding wheel life while maintaining the roughness.
- abrasive grains having an average particle diameter of 2 to 15 ⁇ m are preferred.
- a diamond abrasive grain is suitable, for example.
- the particle size of the abrasive grains can be measured by, for example, an electrical resistance test method.
- the grain size of the abrasive grains in the present invention is an average value (median diameter (D50)) measured by this electrical resistance test method.
- D50 median diameter
- the surface roughness of the end surface after rough grinding is 1 ⁇ m or less in terms of Ra.
- the surface roughness after precision grinding is preferably 0.1 ⁇ m or less in terms of Ra.
- the grinding wheel for precisely grinding the end face of the glass substrate includes abrasive grains and a binder for bonding the abrasive grains as in the configuration 1, and a binder on the surface of the grinding wheel.
- the portion is characterized in that the hardness measured by the nanoindentation test method under the condition of an indentation load of 250 mN using a Berkovich indenter is in the range of 0.4 to 1.7 GPa.
- the present inventor conducted grinding of the grinding wheel evaluated by a method such as a hardness test using a conventional Ogoshi tester or a hardness evaluation using a Rockwell hardness tester, and actually grinding a substrate end face using the grinding wheel.
- the reason why there was no clear correlation with the grinding performance was estimated as follows.
- the hardness test of the conventional grinding wheel destroys the surrounding grinding wheel structure in the process where the indenter sinks into the grinding wheel at the time of measurement and evaluates the compressed structure state, there is a density factor, so the grinding wheel structure Since the total strength is measured, the hardness to show the grinding performance of the grinding wheel, in other words, the mechanical strength of the binder that holds the abrasive grains directly connected to the grinding performance of the grinding stone is accurately evaluated. It is thought that it was not possible.
- the inventor maintains the strength of the structure, particularly the strength between the abrasive grains and the binder (binding agent) that bonds the abrasive grains, in other words, holding the abrasive grains. It was speculated that the grinding performance differs depending on the strength, and that this is likely to cause variations in the end face quality. Therefore, the present inventor has recognized that the hardness of the grindstone, particularly the strength of the bond between the abrasive grains and the binder, is extremely important as the performance or processing characteristics of the grindstone.
- the nanoindentation test method was examined as a method for accurately evaluating the bonding state of the particles, in other words, the holding strength of the abrasive grains.
- the hardness measured by the nano-indentation test method under the predetermined conditions and the grinding performance when grinding the substrate end face using this grinding wheel (grinding speed, grinding surface roughness, shape dimensional accuracy, etc.)
- grinding speed grinding speed
- grinding surface roughness shape dimensional accuracy, etc.
- the hardness of the binder portion on the surface of the grinding wheel measured by the nanoindentation test method using a Berkovich indenter under the condition of an indentation load of 250 mN is within a range of 0.4 to 1.7 GPa.
- a grinding wheel it exhibits good grinding performance, especially in precision grinding of the finish.
- the end face of the glass substrate for magnetic disks can be finished efficiently and with high quality, and stable quality can be achieved even in mass production processing. It was found that it can be obtained.
- FIG. 5 shows the relationship between the load and the displacement when the pressure is reduced at the same unloading speed as that during the pressure increase.
- the mechanical strength of a binder can be evaluated accurately.
- three characteristic curves corresponding to three different grinding wheels are shown. This curve shows the dynamic hardness characteristic, and shows a characteristic closer to that in actual use than the hardness evaluation which is a conventional static hardness characteristic.
- H F / Ac
- H the hardness of the grinding wheel
- F the load
- Ac the indentation area
- the indentation area Ac is represented by the following relational expression.
- the grinding wheel according to the present invention has a hardness measured by the nanoindentation test method in the range of 0.4 to 1.7 GPa, more preferably in the range of 1.2 to 1.6 GPa. is there.
- the process is performed in such an arrangement that the rotation axis of the glass substrate 1 and the rotation axis of the grindstone 7 or the grindstone 8 are parallel to each other.
- the grindstone 7 it contacts with the arrow 19 direction (cutting direction) in a figure with respect to the outer peripheral side end surface of the glass substrate 1, and about the grindstone 8, the arrow 20 in the figure with respect to the inner peripheral side end surface of the glass substrate 1 is shown. Touch the direction (cutting direction).
- the processing while rotating the grindstone 7 or the grindstone 8 and the glass substrate 1 in a predetermined direction, respectively, and the peripheral speed and the peripheral speed ratio of the grindstone 7 or the grindstone 8 and the glass substrate 1 are both internal and external. What is necessary is just to set suitably so that it may be suitable for the grinding process of a peripheral side end surface.
- the glass substrate 1 is rotated in the direction of arrow 10
- the grindstone 7 is rotated in the direction of arrow 17
- the grindstone 8 is rotated in the direction of arrow 18, but the rotation direction is not limited to this.
- the rotation direction of the grindstone 7 or the grindstone 8 and the glass substrate 1 may be the same direction (counter direction) or a different direction (anti-counter direction) in the processed portion.
- the peripheral speed at the processed portion of the grindstone 7 is preferably 800 to 1700 m / min. Further, it is preferable that the peripheral speed at the processed portion of the grindstone 8 is 200 to 700 m / min. In addition, the peripheral speed at the processed portion of the glass substrate 1 is preferably 3 to 10 m / min. Further, at the time of grinding, it is preferable that the back component grinding resistance is 2 to 40 N / mm. Back component grinding resistance is a parameter related to processing pressure. The back component grinding resistance can be measured using, for example, a grinding dynamometer. Further, the grinding fluid (coolant) to be used is not particularly limited, but a water-soluble grinding fluid having a high cooling effect and high safety at the production site is particularly suitable.
- FIG. 2 shows another embodiment of the said end surface grinding method
- (a) is a perspective view
- (b) is the front view which changed direction from (a).
- the end face processing method shown in FIG. 2 is such that the grindstone is brought into contact with the end face of the glass substrate in a state where the rotation axis of the grindstone is inclined with respect to an axis orthogonal to the main surface of the glass substrate.
- the grindstone 2 is used for the outer peripheral end surface, and the inner peripheral end surface is used. Is processed using a grindstone 3.
- the grindstone 2 is formed in a disk shape of a predetermined size as shown in the figure, and has a groove shape on the outer peripheral side thereof in contact with the end surface of the glass substrate.
- the groove shape is a concave shape 6 that is recessed inward in a cross-sectional view.
- the shape illustrated in FIG. 3 is an example, and the present invention is not limited to this.
- the grindstone 3 is formed in a cylindrical shape having a predetermined size as shown in the figure, and on the outer peripheral side thereof, a groove shape (for example, a concave shape as shown in FIG. 3) is formed on the surface that contacts the end surface of the glass substrate. )have.
- processing is performed by bringing the end face of the glass substrate into contact with the grindstone so that the trajectory of the grindstone contacting the end face of the glass substrate is not constant.
- the entire end surface in this case, the side wall surface and the three chamfered surfaces on both sides thereof) are ground simultaneously.
- the grindstone 2 for processing the outer peripheral side of the substrate is processed in a state where the plane direction of the grindstone 2 is inclined by an angle ⁇ with respect to the plane direction of the glass substrate 1.
- the state which inclined the plane direction of the grindstone 3 by angle (beta) with respect to the plane direction of the glass substrate 1, in other words, the rotating shaft of the grindstone 3 which is a rotary grindstone is glass. Processing is performed in an inclined state with respect to a direction orthogonal to the main surface of the substrate.
- the grindstone 2 it contacts with the arrow 13 direction (cutting direction) in the figure with respect to the outer peripheral side end surface of the glass substrate 1, and about the grindstone 3, the arrow 14 in the figure with respect to the inner peripheral side end surface of the glass substrate 1 is shown. Touch the direction (cutting direction).
- the peripheral speed and the peripheral speed ratio are suitable for processing the inner and outer peripheral side end faces. May be set as appropriate.
- the glass substrate 1 is rotated in the direction of the arrow 10
- the grindstone 2 is rotated in the direction of the arrow 11
- the grindstone 3 is rotated in the direction of the arrow 12, but the rotation direction is not limited thereto.
- the rotation direction of the grindstone 2 or the grindstone 3 and the glass substrate 1 may be either the same direction (counter direction) or a different direction (anticounter direction).
- the peripheral speed at the processing portion of the grindstone 2 is preferably set to 1200 to 1700 m / min. Further, the peripheral speed at the processed portion of the grindstone 3 is preferably 300 to 700 m / min. In addition, the peripheral speed at the processed portion of the glass substrate 1 is preferably 3 to 10 m / min. Further, at the time of grinding, it is preferable that the back component grinding resistance is 2 to 40 N / mm.
- the locus of the grindstone 2 that abuts the end surface of the glass substrate 1 is not constant, and the convex portions (abrasive grains) of the grindstone 2 abut and act at random positions with respect to the substrate end surface. Therefore, there is little damage to the substrate, and the surface roughness and in-plane variation of the ground surface are also reduced, so that the ground surface can be finished more smoothly. Therefore, it is preferable to apply the above-described grinding wheel of the present invention as the grinding wheel 2 and the grinding wheel 3 used in the processing method for precision grinding with the grinding wheel tilted with respect to such a glass substrate.
- FIG. 7 shows other embodiment of the said end surface grinding method
- (a) is a perspective view
- (b) is the front view which changed direction from (a).
- About the processing method of the inner peripheral side end surface of a glass substrate it is the same as that of embodiment shown in the above-mentioned FIG. 2, However About an outer peripheral side end surface, a magnitude
- a groove shape is formed on the surface that contacts the end surface of the glass substrate.
- the groove shape is, for example, a concave shape 6 as shown in FIG.
- the glass substrate is in a state where the plane direction of the grindstone 5 is inclined by an angle ⁇ with respect to the plane direction of the glass substrate 1 so that the trajectory of the grindstone 5 contacting the end surface of the glass substrate 1 is not constant. It is preferable to perform processing while bringing the outer peripheral side end face of 1 into contact with the inner peripheral side of the grindstone 5.
- the trajectory of the grindstone 5 that abuts on the outer peripheral end surface of the glass substrate 1 is not constant, and the convex portions (abrasive grains) of the grindstone 5 abut on the substrate end surface at random positions.
- the glass type used for the magnetic disk glass substrate is not particularly limited.
- 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. Among these, amorphous aluminosilicate glass is particularly preferable because it is excellent in smoothness, impact resistance and vibration resistance.
- the present invention also provides the invention according to the following preferred embodiments related to the above-described embodiments. That is, the hardness measured by the nanoindentation test method under the condition of an indentation load of 250 mN using a Barkovic indenter, the binder part of the grinding wheel surface containing abrasive grains and a binder for bonding the abrasive grains, Using this grinding wheel, a correlation with the grinding speed when the glass substrate end face is ground under certain conditions is obtained in advance. And based on this calculated
- the present inventor has recognized that the hardness of the grindstone, particularly the strength of the bond between the abrasive grains and the binder, is extremely important as the performance or processing characteristics of the grindstone, and nanoindentation under predetermined conditions. Clarity between the hardness measured by the test method and the grinding performance (grinding speed, grinding surface roughness, shape dimensional accuracy, etc.) when the substrate end face grinding is actually performed under certain search conditions using this grinding wheel We found that a good correlation was observed. Specifically, the binder portion on the surface of the grinding wheel is made of glass with a hardness measured by a nanoindentation test method using a Barkovic indenter under an indentation load of 250 mN and a predetermined condition using this grinding wheel.
- the correlation with the grinding speed when the substrate end face is ground is obtained in advance. Then, based on the obtained correlation, a grinding wheel having a hardness that achieves a desired grinding speed is selected, and the end surface of the glass substrate is ground using the selected grinding wheel, so that the finishing surface is particularly finished. It has been found that excellent grinding performance is exhibited in precision grinding, and as a result, the end face of the glass substrate for magnetic disks can be efficiently finished with high quality, and stable quality can be obtained even in mass production processing.
- FIG. 6 shows the results in the examples described later, and will be described in detail in the examples. Based on the correlation shown in FIG. 6, a desired grinding speed, for example, a range of A that is 0.5 ⁇ m / sec or more is set as the optimum range. Then, by selecting a grinding wheel having a hardness within the optimum range of A and finely grinding the end surface of the glass substrate using the selected grinding wheel, good grinding performance can be exhibited.
- the present inventor preferably has a hardness measured by the nanoindentation test method in the range of 0.4 to 1.7 GPa, In precision grinding, it has been found that a desired grinding speed of, for example, 1.0 ⁇ m / sec or more can be obtained, good grinding performance can be exhibited, and stable quality can be obtained even in mass production.
- the hardness is particularly preferably in the range of 1.2 to 1.6 GPa.
- the grinding stone 2 and the grinding stone 3 used in the processing method for precision grinding in a state where the grinding stone is tilted with respect to the glass substrate as shown in FIG. 2 or FIG. 7 is measured by the nano indentation test method described above. It is preferable to apply the grinding wheel selected based on the correlation between the hardness of the grinding wheel and the grinding speed when the end surface of the glass substrate is ground using the grinding wheel under predetermined conditions.
- the glass substrate that has been ground on the outer peripheral side and inner peripheral side end surface thereof is subjected to end surface polishing by brushing or the like, and the end surface is processed into a mirror surface. Subsequent to this, a mirror polishing process of the main surface, a chemical strengthening process, and the like are performed to obtain a glass substrate 1 for magnetic disk as shown in FIG.
- 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.
- the magnetic layer may be, for example, an alloy having a Co-based hcp crystal structure for a perpendicular magnetic recording medium.
- a protective layer a carbon-type protective layer etc. are mentioned preferably, for example.
- the lubricant that forms the lubricating layer on the protective layer include PFPE (perfluoropolyether) compounds.
- PFPE perfluoropolyether
- 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.
- the end face of the substrate can be finished with high quality, and the surface state and shape of the substrate end face It is possible to provide a magnetic disk capable of preventing occurrence of a failure due to accuracy and realizing further higher recording density.
- a glass substrate (glass disk) made of a disc-shaped amorphous aluminosilicate glass having a diameter of 66 mm ⁇ was obtained from a molten glass by direct pressing using an upper die, a lower die, and a barrel die.
- the grindstone hardness was measured by the above-described nanoindentation test method.
- the rough grinding is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 1 and the precision grinding is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. was set to 10 degrees.
- the peripheral speed, rotation direction, and processing pressure of each of the glass substrate and the grindstone were set as appropriate.
- the inner peripheral side end faces of 100 glass substrates were ground.
- the corner portion A formed by the side wall surface and the chamfered surface and the main surface and the chamfered surface was measured using a fine contour shape measuring instrument.
- the radius of curvature a total of two points were measured, one on each side of the substrate, and the average value was taken as the measured value of the substrate. This was repeated for 100 substrates, and the variation (difference between the maximum value and the minimum value) was calculated. The results were evaluated in the following four stages and are shown in Table 1.
- Example 8 to 13 For the above precision grinding process, diamond abrasive grains and a resin bond grindstone in which the binder for bonding the diamond abrasive grains is a phenol resin, the hardness measured by the nanoindentation test method is 1.3 GPa, and the average Six types of grindstones with different particle sizes in the range of 1.5 to 25 ⁇ m were prepared. Except that the above grindstone was used, the inner peripheral side end face of the glass substrate was ground in the same manner as in Example 1, the obtained glass substrate was evaluated in the same manner as in Example 1, and the results are shown. It was shown in 2.
- Example 101 to 103 Comparative Examples 101 and 102
- a glass substrate made of disc-shaped aluminosilicate glass having a diameter of 66 mm ⁇ was obtained from molten glass by direct pressing using an upper die, a lower die, and a barrel die in the same manner as in the above-described example.
- a lapping process was performed on the glass substrate in order to improve dimensional accuracy and shape accuracy.
- the end face grinding of the glass substrate was performed using the above-mentioned ten types of resin bond grindstones for precision grinding under the same conditions as the main processing, and measured by the above-mentioned nanoindentation test method.
- the correlation between the grinding wheel hardness and the grinding speed was determined and shown in FIG. In FIG. 6, the range of A in which the grinding speed is 0.5 ⁇ m / sec or more is set as the optimal range, and three types of grinding wheels having hardness within the optimal range of A are selected.
- One type of grinding wheel in the region B having low hardness was selected, and one type of grinding wheel in the region C having higher grinding wheel hardness than the optimum range was selected.
- the optimum range was 0.4 to 1.7 GPa.
- the holding strength of the abrasive grains is low, and the falling of the abrasive grains is promoted during processing, resulting in a spilled state. It is thought that it is in a state. Further, when a grinding wheel selected from a region having a hardness higher than the optimum range was used (Comparative Example 102), a good grinding speed could not be obtained. Also, good results were not obtained in terms of end surface roughness, end shape and dimensional accuracy. In this case, the holding strength of the abrasive grains is too high, and the self-generated blade action does not advance due to the falling off of the abrasive grains.
- Examples 201 to 212 Comparative examples 201 to 208
- a glass substrate made of disc-shaped aluminosilicate glass having a diameter of 66 mm ⁇ was obtained from molten glass by direct pressing using an upper die, a lower die, and a barrel die.
- a lapping process was performed on the glass substrate in order to improve dimensional accuracy and shape accuracy.
- a cylindrical grindstone is used to make a hole in the central portion of the glass substrate, and the outer peripheral end face is roughly ground by a processing method using the overall grindstone as shown in FIG. Precision grinding was performed by the method described below.
- An electrodeposition bond grindstone in which diamond abrasive grains are hardened with an electrodeposition bond was used for the above rough grinding.
- a resin bond grindstone containing diamond abrasive grains having an average abrasive grain size of 5 ⁇ m and a phenol resin as a binder was used.
- This resin-bonded grindstone has the same constituent material, but five types of grindstones having different binder part hardnesses were prepared. The hardness of the binder part of the grindstone was measured by the nanoindentation test method described above.
- the precision grinding process was performed in the following four ways.
- the first method was performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 1 described above (indicated as “external circumstance (FIG. 1)” in Table 4).
- the second method is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 7 described above, and the inclination angle of the grindstone with respect to the glass substrate is 0 degree (that is, there is no inclination) (“Inscribed” in Table 4).
- the third method is performed by the positional relationship between the glass substrate and the grindstone shown in FIG.
- the inclination angle ⁇ of the grindstone with respect to the glass substrate is set to 10 degrees (in Table 4, “circumscribed / inclined (FIG. 2 ) ").
- the fourth method is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 7, and the inclination angle ⁇ of the grindstone with respect to the glass substrate is set to 10 degrees (in Table 4, “inscribed / inclined (figure 7) ”). Note that the peripheral speed, rotation direction, and processing pressure of each of the glass substrate and the grindstone were set appropriately.
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Abstract
Description
磁気ディスク用ガラス基板は、通常、円盤状に成形したガラス素板に、端面の研削・研磨、主表面の研削・研磨、化学強化等の工程を順次施して製造される。 In addition, in order to increase the recording density of the magnetic disk, high processing accuracy is required for the glass substrate, which is the same not only for the main surface of the glass substrate but also for the end face shape.
A glass substrate for a magnetic disk is usually manufactured by subjecting a glass base plate formed into a disk shape to steps such as end face grinding / polishing, main surface grinding / polishing, and chemical strengthening sequentially.
その理由は、たとえばHDDに搭載された時の磁気ヘッドの位置決め精度を得るための内外径寸法精度の高精度化、媒体主表面に対するコロージョン発生などのコンタミ要因の低減要請に基づく外径端面の高品位化の達成が要求されるからである。 With the development of the information society, the demand for higher recording density of magnetic disks is only increasing. In the end face shape of a glass substrate for a magnetic disk, further improvement in surface quality (smoothing etc.) and improvement in processing accuracy (form accuracy etc.) have been demanded.
The reason for this is that, for example, the outer diameter of the outer end surface is increased based on a request to reduce contamination factors such as the increase in the inner and outer diameter dimensional accuracy to obtain the positioning accuracy of the magnetic head when mounted on the HDD and the occurrence of corrosion on the medium main surface. This is because achievement of quality is required.
すなわち、本発明は、前記課題を解決するため、以下の構成としている。
(構成1)
中心に円孔を有する円盤状のガラス基板の端面を精密研削するための、研削砥石であって、前記研削砥石は、砥粒と、該砥粒同士を結合するバインダーとを含み、前記研削砥石表面のバインダー部分を、バーコビッチ圧子を用いて、250mNの押込み荷重の条件でナノインデンテーション試験法によって測定される硬度が、0.4~1.7GPaの範囲内であることを特徴とする研削砥石。 As a result of intensive studies to solve the above problems, the present inventor has completed the present invention.
That is, the present invention has the following configuration in order to solve the above problems.
(Configuration 1)
A grinding wheel for precisely grinding an end face of a disk-shaped glass substrate having a circular hole in the center, wherein the grinding wheel includes abrasive grains and a binder for bonding the abrasive grains, and the grinding wheel A grinding wheel characterized in that the hardness of the binder part on the surface measured by the nanoindentation test method under the condition of indentation load of 250 mN using a Berkovich indenter is in the range of 0.4 to 1.7 GPa .
前記砥粒の平均粒子径は、2~15μmの範囲内であることを特徴とする構成1に記載の研削砥石。 (Configuration 2)
2. The grinding wheel according to
前記研削砥石は、前記ガラス基板の主表面と直交する軸に対して砥石の回転軸を傾斜させた状態で当該砥石を前記ガラス基板の端面に当接させて当該ガラス基板の端面を研削処理する際に用いる回転砥石であることを特徴とする構成1又は2に記載の研削砥石。
ここで、上記「傾斜」とは、ガラス基板の側壁面と2つの面取面の全ての面が、研削砥石の表面に設けられた溝に同時に接触するように、傾斜させることである。
(構成4)
構成1乃至3のいずれかに記載の研削砥石を用いて、前記ガラス基板の端面の研削処理を行う工程を含むことを特徴とする磁気ディスク用ガラス基板の製造方法。 (Configuration 3)
The grinding wheel grinds the end surface of the glass substrate by bringing the grindstone into contact with the end surface of the glass substrate in a state where the rotation axis of the grindstone is inclined with respect to an axis orthogonal to the main surface of the glass substrate. The grinding wheel according to
Here, the above “inclination” means to incline so that all the surfaces of the side wall surface and the two chamfered surfaces of the glass substrate are simultaneously in contact with grooves provided on the surface of the grinding wheel.
(Configuration 4)
A method for producing a glass substrate for a magnetic disk, comprising the step of grinding an end face of the glass substrate using the grinding wheel according to any one of
中心に円孔を有する円盤状のガラス基板の端面を研削砥石を用いて精密研削する研削処理を含む磁気ディスク用ガラス基板の製造方法であって、前記研削砥石は、砥粒と、当該砥粒同士を結合するバインダーとを含み、前記研削砥石表面のバインダー部分を、バーコビッチ圧子を用いて、250mNの押込み荷重の条件でナノインデンテーション試験法によって測定される硬度と、この研削砥石を用いて、ある条件でガラス基板端面を研削処理したときの研削速度との相関関係を予め求めておき、求められた相関関係に基づき、所望の研削速度となるような硬度を有する研削砥石を選択し、この選択された研削砥石を用いて前記研削処理を行うことを特徴とする磁気ディスク用ガラス基板の製造方法。 (Configuration 5)
A method for producing a glass substrate for a magnetic disk including a grinding process for precisely grinding an end face of a disk-shaped glass substrate having a circular hole in the center using a grinding wheel, the grinding wheel comprising abrasive grains and the abrasive grains And a binder part on the surface of the grinding wheel using a Barkovic indenter, a hardness measured by a nanoindentation test method under a pressing load condition of 250 mN, and using this grinding wheel, The correlation with the grinding speed when the glass substrate end face is ground under certain conditions is obtained in advance, and based on the obtained correlation, a grinding wheel having a hardness that provides a desired grinding speed is selected. A method for producing a glass substrate for a magnetic disk, wherein the grinding process is performed using a selected grinding wheel.
前記研削砥石は、前記バインダーが樹脂材料からなり、前記ナノインデンテーション試験法によって測定される硬度が、0.4~1.7GPaの範囲内であることを特徴とする構成5に記載の磁気ディスク用ガラス基板の製造方法。 (Configuration 6)
6. The magnetic disk according to
前記選択された研削砥石を用いて、前記ガラス基板の主表面と直交する軸に対して当該研削砥石の回転軸を傾斜させた状態で当該研削砥石を前記ガラス基板の端面に当接させて当該ガラス基板の端面を研削処理することを特徴とする構成5又は6に記載の磁気ディスク用ガラス基板の製造方法。 (Configuration 7)
Using the selected grinding wheel, the grinding wheel is brought into contact with the end surface of the glass substrate in a state where the rotation axis of the grinding wheel is inclined with respect to an axis orthogonal to the main surface of the glass substrate. The method for producing a glass substrate for a magnetic disk according to
前記ガラス基板の端面の表面粗さRaが、0.1μm以下になるように研削処理することを特徴とする構成4乃至7のいずれかに記載の磁気ディスク用ガラス基板の製造方法。
(構成9)
構成4乃至8のいずれかに記載の磁気ディスク用ガラス基板の製造方法によって製造された磁気ディスク用ガラス基板の主表面上に少なくとも磁性層を形成することを特徴とする磁気ディスクの製造方法。 (Configuration 8)
The method for producing a glass substrate for a magnetic disk according to any one of the
(Configuration 9)
A magnetic disk manufacturing method comprising: forming at least a magnetic layer on a main surface of a magnetic disk glass substrate manufactured by the magnetic disk glass substrate manufacturing method according to any one of
また、本発明に係る磁気ディスク用ガラス基板の製造方法によれば、この研削砥石を用いて、量産加工においても安定した品質の端面研削加工を行うことができるため、その結果、磁気ディスク用ガラス基板の端面を高品質に仕上げることができる。 According to the grinding wheel of the present invention, the end surface of the magnetic disk glass substrate can be efficiently finished with high quality, and stable quality can be obtained even in mass production processing. Therefore, it is possible to meet the demand for higher recording density of the magnetic disk, which is urgently required to ensure reliability.
Further, according to the method for manufacturing a glass substrate for magnetic disk according to the present invention, it is possible to perform end surface grinding with stable quality even in mass production using this grinding wheel, and as a result, glass for magnetic disk is obtained. The end face of the substrate can be finished with high quality.
図4は、本発明が適用される磁気ディスク用ガラス基板1の外周側端部の断面図である。該ガラス基板1は、図4には示されていないが、中心部に円孔4を有する全体が円盤状に形成され(図1等を参照)、その表裏の主表面1a,1aと、これら主表面1a,1a間に形成される外周側の端面と内周側の端面を有する。
上記ガラス基板1の外周側の端面は、その主表面1aと直交する側壁面1bと、この側壁面1bと表裏の主表面1a,1aとの間にそれぞれ形成されている2つの面取り面(面取りした面)1c、1cとからなる形状に形成されている。また、上記ガラス基板1の内周側の端面については図示していないが、上記外周側端面と同様に、その主表面1aと直交する側壁面と、この側壁面と表裏の主表面1a,1aとの間にそれぞれ形成されている2つの面取り面(面取りした面)とからなる形状に形成されている。 Hereinafter, embodiments for carrying out the present invention will be described in detail.
FIG. 4 is a cross-sectional view of the outer peripheral end of the magnetic
The outer peripheral end surface of the
ここで、本発明においては、Ra、Rmaxというときは、日本工業規格(JIS)B0601:1982に準拠する算術平均粗さ、最大粗さのことである。また、本発明において端面の表面粗さは、レーザー顕微鏡を用いて観察倍率を3000倍にして50μm×50μmの測定領域で測定した値である。 The main surface 1a, the outer peripheral side end surface, and the inner peripheral side end surface of the
Here, in the present invention, Ra and Rmax are arithmetic average roughness and maximum roughness according to Japanese Industrial Standard (JIS) B0601: 1982. In the present invention, the surface roughness of the end face is a value measured in a measurement region of 50 μm × 50 μm using a laser microscope with an observation magnification of 3000 times.
まず、上記ガラス基板1の端面の研削・研磨工程について説明する。
なお、本明細書においては、ダイレクトプレス等により所定の円板状に成形したガラスディスクから、このガラスディスクに加工、処理等を施して作製される最終製品のガラス基板にいたるまで、説明の便宜上、すべてガラス基板もしくは磁気ディスク用ガラス基板と呼ぶこととする。 The
First, the grinding / polishing process of the end face of the
In the present specification, for convenience of explanation, from a glass disk molded into a predetermined disk shape by direct press or the like to a final product glass substrate produced by processing, processing, etc. on this glass disk. These are all referred to as glass substrates or magnetic disk glass substrates.
中心部に孔明け加工を施し、円孔4を有するガラス基板1に対して、その外周側端面については砥石7を、内周側端面に対しては砥石8を用いて加工する。砥石7は、図示するように所定の大きさの円盤状に形成されており、その外周側には、ガラス基板の端面形状を形成するための溝形状を有しており、具体的には、ガラス基板の外周側端面に側壁面と面取り面の両方の面を形状転写できるような溝形状となっている。また、砥石8は、図示するように所定の大きさの円柱状に形成されており、その外周側には、ガラス基板の端面形状を形成するための溝形状を有しており、具体的には、ガラス基板の内周側端面に側壁面と面取り面の両方の面を形状転写できるような溝形状となっている。つまり、上記砥石7と砥石8は、いずれもガラス基板1の研削加工面の仕上がり目標の寸法形状を考慮して、所定の寸法形状に形成されている。 First, the end face grinding process will be described. 1A and 1B show an embodiment of the end face grinding method, wherein FIG. 1A is a perspective view and FIG. 1B is a front view in which the direction is changed from FIG.
A drilling process is performed at the center, and the
また、砥粒の粒径としては、粗さを維持しながら砥石寿命全体に亘って研削性能を維持できるためには、例えば平均粒子径30μm以下の砥粒が好適であるが、特に精密研削加工用には、平均粒子径2~15μmの範囲内の砥粒が好適である。砥粒としては、例えばダイヤモンド砥粒が好適である。砥粒の粒径は、例えば電気抵抗試験法で測定することが可能である。
本発明における砥粒の粒径は、この電気抵抗試験法によって測定された平均値(メジアン径(D50))である。
なお、粗研削加工後の端面の表面粗さはRaで1μm以下とすることが好ましい。また、精密研削後の表面粗さはRaで0.1μm以下とすることが好ましい。 As the
In addition, as the grain size of the abrasive grains, for example, abrasive grains having an average grain diameter of 30 μm or less are suitable in order to maintain the grinding performance over the entire grinding wheel life while maintaining the roughness. For use, abrasive grains having an average particle diameter of 2 to 15 μm are preferred. As an abrasive grain, a diamond abrasive grain is suitable, for example. The particle size of the abrasive grains can be measured by, for example, an electrical resistance test method.
The grain size of the abrasive grains in the present invention is an average value (median diameter (D50)) measured by this electrical resistance test method.
In addition, it is preferable that the surface roughness of the end surface after rough grinding is 1 μm or less in terms of Ra. Moreover, the surface roughness after precision grinding is preferably 0.1 μm or less in terms of Ra.
従来の研削砥石の硬さ試験は、圧子が測定時に砥石に沈み込む過程で周囲の砥石組織を破壊し、且つ圧縮した組織状態を評価することから密度的要素が介在するため、砥石構造体の総合的な強度を測定していることになり、砥石の研削性能を発揮させるための硬さ、言い換えれば砥石の研削性能に直接つながる砥粒同士を保持するバインダーの機械的強度を的確に評価することができなかったものと考えられる。 The present inventor conducted grinding of the grinding wheel evaluated by a method such as a hardness test using a conventional Ogoshi tester or a hardness evaluation using a Rockwell hardness tester, and actually grinding a substrate end face using the grinding wheel. The reason why there was no clear correlation with the grinding performance (grinding speed, ground surface roughness, shape dimensional accuracy, etc.) was estimated as follows.
Since the hardness test of the conventional grinding wheel destroys the surrounding grinding wheel structure in the process where the indenter sinks into the grinding wheel at the time of measurement and evaluates the compressed structure state, there is a density factor, so the grinding wheel structure Since the total strength is measured, the hardness to show the grinding performance of the grinding wheel, in other words, the mechanical strength of the binder that holds the abrasive grains directly connected to the grinding performance of the grinding stone is accurately evaluated. It is thought that it was not possible.
測定対象となる研削砥石表面のバインダー部分を、先端が四角錐形状のバーコビッチ圧子を用いて、1nm/秒で荷重を負荷し、250mNまで昇圧し、そのまま所定時間(例えば10秒間)保持した後、昇圧時と同等の除荷速度にて減圧した際の荷重と変位の関係を図5に示した。なお、この昇圧条件であれば、バインダーの機械的強度を的確に評価することができる。
ここでは、例として3個の異なる研削砥石に対応する3本の特性曲線を示している。この曲線は動的硬さ特性を示しており、従来の静的硬さ特性である硬度評価よりも実使用時に近い特性を示している。 Next, a method for measuring the hardness of the grinding wheel by the nanoindentation test method will be described.
The binder part on the surface of the grinding wheel to be measured was loaded with a load of 1 nm / second using a square pyramid-shaped barkovic indenter, pressurized to 250 mN, and held for a predetermined time (for example, 10 seconds). FIG. 5 shows the relationship between the load and the displacement when the pressure is reduced at the same unloading speed as that during the pressure increase. In addition, if it is this pressurization condition, the mechanical strength of a binder can be evaluated accurately.
Here, as an example, three characteristic curves corresponding to three different grinding wheels are shown. This curve shows the dynamic hardness characteristic, and shows a characteristic closer to that in actual use than the hardness evaluation which is a conventional static hardness characteristic.
H=F/Ac
ここで、Hは研削砥石の硬度、Fは荷重、Acはくぼみ面積である。
上記くぼみ面積Acは、下記の関係式によって表わされる。
Ac=f(hc) ∝ 24.5・hc2
hc=hmax-ε・F/S
ここで、hc:押込み深さ、hmax:最大荷重時の深さ、hs:除荷開始時の押込み深さ、ho:除荷後の押込み深さ、ε:圧子固有の形状係数(例:バーコビッチ圧子の場合=0.75)、S:荷重と変位の比例係数、m:傾き(dF/dh)。 From the result of the dynamic hardness characteristic curve shown in FIG. 5, the hardness of the grinding wheel by the nanoindentation test method is obtained by the following formula.
H = F / Ac
Here, H is the hardness of the grinding wheel, F is the load, and Ac is the indentation area.
The indentation area Ac is represented by the following relational expression.
Ac = f (hc) ∝ 24.5 · hc 2
hc = hmax-ε · F / S
Where hc: depth of indentation, hmax: depth at maximum load, hs: depth of indentation at the start of unloading, ho: depth of indentation after unloading, ε: shape factor specific to indenter (example: Berkovich) In the case of an indenter = 0.75), S: proportional coefficient of load and displacement, m: inclination (dF / dh).
この場合、砥石7又は砥石8、及びガラス基板1をそれぞれ所定方向に回転させながら加工を行うことが好ましく、砥石7又は砥石8、及びガラス基板1の各々の周速度、周速度比については内外周側端面の研削加工に好適なように適宜設定されればよい。図1では、ガラス基板1は矢印10方向に、砥石7は矢印17方向に、砥石8は矢印18方向にそれぞれ回転させているが、回転方向はこれに限定されるわけではない。砥石7又は砥石8とガラス基板1の回転方向は、加工部において同方向(カウンタ方向)、異方向(アンチカウンタ方向)のいずれでもよい。 In the end face grinding process, as shown in FIG. 1, the process is performed in such an arrangement that the rotation axis of the
In this case, it is preferable to perform the processing while rotating the
また、研削加工時は、背分力研削抵抗が2~40N/mmとすることが好適である。背分力研削抵抗は加工圧に関連するパラメータである。なお、背分力研削抵抗は、例えば、研削動力計を用いて測定することができる。
また、使用する研削液(クーラント)としては、特に制約はないが、冷却効果が高く、生産現場において安全性の高い水溶性の研削液が特に好適である。 From the viewpoint of grindability and processing efficiency, for example, the peripheral speed at the processed portion of the
Further, at the time of grinding, it is preferable that the back component grinding resistance is 2 to 40 N / mm. Back component grinding resistance is a parameter related to processing pressure. The back component grinding resistance can be measured using, for example, a grinding dynamometer.
Further, the grinding fluid (coolant) to be used is not particularly limited, but a water-soluble grinding fluid having a high cooling effect and high safety at the production site is particularly suitable.
図2に示す端面加工方法は、前記ガラス基板の主表面と直交する軸に対して砥石の回転軸を傾斜させた状態で当該砥石を前記ガラス基板の端面に当接させて当該ガラス基板の端面を研削加工する方法である。このような研削加工方法は、表面粗さなどの加工品位と形状精度を高めることができるので、たとえば総形砥石を用いて粗研削加工を行った後の精密研削加工に特に好適である。なお、粗研削加工に用いることも可能である。 Moreover, FIG. 2 shows another embodiment of the said end surface grinding method, (a) is a perspective view, (b) is the front view which changed direction from (a).
The end face processing method shown in FIG. 2 is such that the grindstone is brought into contact with the end face of the glass substrate in a state where the rotation axis of the grindstone is inclined with respect to an axis orthogonal to the main surface of the glass substrate. Is a grinding method. Since such a grinding method can improve the processing quality such as surface roughness and the shape accuracy, it is particularly suitable for precision grinding after rough grinding using, for example, a general-purpose grindstone. It can also be used for rough grinding.
例えば、図2に示されるように、基板外周側を加工する砥石2については、ガラス基板1の平面方向に対して砥石2の平面方向を角度αだけ傾けた状態で加工する。また、基板内周側を加工する砥石3については、ガラス基板1の平面方向に対して砥石3の平面方向を角度βだけ傾けた状態、換言すると、回転砥石である砥石3の回転軸をガラス基板の主表面と直交する方向に対して傾斜させた状態で加工する。砥石2については、ガラス基板1の外周側端面に対して図中の矢印13方向(切込み方向)に接触し、砥石3については、ガラス基板1の内周側端面に対して図中の矢印14方向(切込み方向)に接触する。この場合においても、砥石2又は砥石3、及びガラス基板1をそれぞれ所定方向に回転させながら加工を行うことが好ましく、各々の周速度、周速度比については内外周側端面の加工に好適なように適宜設定されればよい。また、図2では、ガラス基板1は矢印10方向に、砥石2は矢印11方向に、砥石3は矢印12方向にそれぞれ回転させているが、回転方向はこれに限定されるわけではない。砥石2又は砥石3とガラス基板1の回転方向は、同方向(カウンタ方向)、異方向(アンチカウンタ方向)のいずれでもよい。 In the case of this processing method, processing is performed by bringing the end face of the glass substrate into contact with the grindstone so that the trajectory of the grindstone contacting the end face of the glass substrate is not constant. In this processing method, the entire end surface (in this case, the side wall surface and the three chamfered surfaces on both sides thereof) are ground simultaneously.
For example, as shown in FIG. 2, the
従って、このようなガラス基板に対して砥石を傾けた状態で精密研削する加工法において用いられる上記砥石2および砥石3としては、上述の本発明の研削砥石を適用することが好適である。 In the processing method shown in FIG. 2, the locus of the
Therefore, it is preferable to apply the above-described grinding wheel of the present invention as the
ガラス基板の内周側端面の加工方法については、上述の図2に示す実施の形態と同様であるが、外周側端面については、図7に示すようなガラス基板が内包されるような大きさの円筒状に形成された砥石5を用いて加工を行う方法を適用することもできる。砥石5の内周側には、ガラス基板の端面と接触する面に溝形状を有している。この溝形状は、例えば前述の図3に示すような凹形状6となっている。
本実施の形態においても、ガラス基板1の端面に当接する砥石5の軌跡が一定とならないように、ガラス基板1の平面方向に対して砥石5の平面方向を角度αだけ傾けた状態でガラス基板1の外周側端面と砥石5の内周側とを接触させながら加工することが好適である。図7に示す加工方法では、ガラス基板1の外周端面に当接する砥石5の軌跡が一定とはならないで、砥石5の凸部(砥粒)が基板端面に対してランダムな位置に当接、作用するため、基板へのダメージが少なく、研削加工面の表面粗さやその面内ばらつきも小さくなり、研削加工面をより高平滑に仕上げることができる。従って、このような図7に示す加工方法において用いられる上記砥石5としては、上述の本発明の研削砥石を適用することが好適である。
なお、磁気ディスク用ガラス基板に用いる硝種としては特に限定を設けないが、ガラス基板の材質としては、例えば、アルミノシリケートガラス、ソーダライムガラス、ソーダアルミノシリケートガラス、アルミノボロシリケートガラス、ボロシリケートガラス、石英ガラス、チェーンシリケートガラス、又は結晶化ガラス等のガラスセラミックス等が挙げられる。なかでもアモルファスのアルミノシリケートガラスは、平滑性、耐衝撃性や耐振動性に優れるため特に好ましい。 Moreover, FIG. 7 shows other embodiment of the said end surface grinding method, (a) is a perspective view, (b) is the front view which changed direction from (a).
About the processing method of the inner peripheral side end surface of a glass substrate, it is the same as that of embodiment shown in the above-mentioned FIG. 2, However About an outer peripheral side end surface, a magnitude | size which a glass substrate as shown in FIG. It is also possible to apply a method of processing using the
Also in the present embodiment, the glass substrate is in a state where the plane direction of the
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. Among these, amorphous aluminosilicate glass is particularly preferable because it is excellent in smoothness, impact resistance and vibration resistance.
すなわち、砥粒と、該砥粒同士を結合するバインダーとを含む研削砥石表面のバインダー部分を、バーコビッチ圧子を用いて、250mNの押込み荷重の条件でナノインデンテーション試験法によって測定される硬度と、この研削砥石を用いて、ある条件でガラス基板端面を研削処理したときの研削速度との相関関係を予め求めておく。そして、この求められた相関関係に基づき、所望の研削速度となるような硬度を有する研削砥石を選択する。そして、この選択された研削砥石を用いてガラス基板の端面を精密研削する研削処理を行う。 The present invention also provides the invention according to the following preferred embodiments related to the above-described embodiments.
That is, the hardness measured by the nanoindentation test method under the condition of an indentation load of 250 mN using a Barkovic indenter, the binder part of the grinding wheel surface containing abrasive grains and a binder for bonding the abrasive grains, Using this grinding wheel, a correlation with the grinding speed when the glass substrate end face is ground under certain conditions is obtained in advance. And based on this calculated | required correlation, the grinding stone which has the hardness which becomes a desired grinding speed is selected. And the grinding process which carries out the precision grinding of the end surface of a glass substrate using this selected grinding wheel is performed.
この図6に示された相関関係に基づき、所望の研削速度、例えば0.5μm/sec以上となるAの範囲を最適範囲とする。そして、このAの最適範囲内の硬度を有する研削砥石を選択し、この選択された研削砥石を用いてガラス基板の端面を精密研削することにより、良好な研削性能を発揮させることができる。 Correlation between the grinding wheel hardness measured by the above-mentioned nano-indentation test method and the grinding speed when the glass substrate end face is ground under a predetermined condition for a plurality of grinding wheels. An example is shown in FIG. FIG. 6 shows the results in the examples described later, and will be described in detail in the examples.
Based on the correlation shown in FIG. 6, a desired grinding speed, for example, a range of A that is 0.5 μm / sec or more is set as the optimum range. Then, by selecting a grinding wheel having a hardness within the optimum range of A and finely grinding the end surface of the glass substrate using the selected grinding wheel, good grinding performance can be exhibited.
また、上記最適範囲内よりも砥石硬度の高いCの領域内の研削砥石を選択した場合、砥粒の保持強度が大きすぎて砥粒の脱落による自生発刃作用が進まず、研削屑が砥石表面に堆積する目詰まりや砥粒の摩滅による目つぶれが発生することで、所望の研削速度が得られず、加工面にもヤケによる品質劣化が発生する。 On the other hand, when a grinding wheel in the region B having a grinding wheel hardness lower than the optimum range is selected, the holding strength of the abrasive grains is low, and the falling of the abrasive grains is promoted during processing, resulting in a spilled state. Thus, the grinding speed cannot be obtained, and shape distortion occurs and the end face quality deteriorates.
In addition, when a grinding wheel in the region C having a grinding wheel hardness higher than the above optimum range is selected, the holding strength of the abrasive grains is too high, and the self-developing action due to the falling off of the abrasive grains does not proceed, so that the grinding scraps are removed from the grinding wheel. Since clogging accumulated on the surface and crushing due to abrasion of the abrasive grains occur, a desired grinding speed cannot be obtained, and quality degradation due to burns also occurs on the processed surface.
すなわち、例えば上述の本発明に係る実施の形態により得られる磁気ディスク用ガラス基板上に、少なくとも磁性層を形成することにより磁気ディスクが得られる。通常は、例えばガラス基板上に、付着層、軟磁性層、下地層、磁性層、保護層、潤滑層などを設けた磁気ディスクとするのが好適である。 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.
また、保護層としては、例えば、炭素系保護層などが好ましく挙げられる。また、保護層上の潤滑層を形成する潤滑剤としては、PFPE(パーフロロポリエーテル)系化合物が挙げられる。
ガラス基板上に上記各層を成膜する方法については、公知のスパッタリング法などを用いることができる。炭素系保護層の成膜についてはプラズマCVD法も好ましく用いられる。また、潤滑層の成膜にはディップ法などを用いることができる。
本発明による磁気ディスク用ガラス基板の製造方法によって製造された磁気ディスク用ガラス基板を用いて磁気ディスクを製造することにより、基板の端面を高品質に仕上げることができ、基板端面の表面状態や形状精度が起因する障害の発生を防止し、より一層の高記録密度化を実現できる磁気ディスクを提供することができる。 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 producing a magnetic disk using the glass substrate for magnetic disk produced by the method for producing a glass substrate for magnetic disk according to the present invention, the end face of the substrate can be finished with high quality, and the surface state and shape of the substrate end face It is possible to provide a magnetic disk capable of preventing occurrence of a failure due to accuracy and realizing further higher recording density.
(実施例1~7、比較例1~3)
まず、溶融ガラスから上型、下型、胴型を用いたダイレクトプレスにより直径66mmφの円盤状のアモルファスのアルミノシリケートガラスからなるガラス基板(ガラスディスク)を得た。 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.
(Examples 1 to 7, Comparative Examples 1 to 3)
First, a glass substrate (glass disk) made of a disc-shaped amorphous aluminosilicate glass having a diameter of 66 mmφ was obtained from a molten glass by direct pressing using an upper die, a lower die, and a barrel die.
上記の粗研削加工にはダイヤモンド砥粒を電着ボンドで固めた電着ボンド砥石を使用した。また、上記の精密研削加工には、平均粒子径(D50)が5μmのダイヤモンド砥粒を用い、当該砥粒同士を結合するバインダーがフェノール樹脂であるレジンボンド砥石を使用した。このレジンボンド砥石は、構成材料は同じであるが、硬度の異なる砥石を準備した。砥石硬度は、上述のナノインデンテーション試験法により測定した。
上記粗研削加工は、前述の図1に示すガラス基板と砥石との配置関係で行い、上記精密研削加工は、前述の図2に示すガラス基板と砥石との配置関係で行い、ガラス基板に対する砥石の傾き角度αは10度に設定した。また、ガラス基板と砥石の各々の周速度、回転方向、加工圧は適宜設定して行った。 Next, a hole is made in the central portion of the glass substrate using a cylindrical grindstone, and the inner peripheral side end face is roughly ground by a machining method using the overall grindstone as shown in FIG. Then, precision grinding was performed by a method in which the grinding stone was brought into contact with the glass substrate as shown in FIG.
An electrodeposition bond grindstone in which diamond abrasive grains are hardened with an electrodeposition bond was used for the above rough grinding. In addition, for the above precision grinding, diamond abrasive grains having an average particle diameter (D50) of 5 μm were used, and a resin bond grindstone in which a binder for bonding the abrasive grains was a phenol resin was used. This resin-bonded grindstone was composed of the same constituent material but different hardness. The grindstone hardness was measured by the above-described nanoindentation test method.
The rough grinding is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 1 and the precision grinding is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. Was set to 10 degrees. The peripheral speed, rotation direction, and processing pressure of each of the glass substrate and the grindstone were set as appropriate.
得られた100枚のガラス基板について、内周側端面の側壁面と面取り面の形状・寸法精度を確認するために、側壁面と面取り面との成す角部Aおよび主表面と面取り面との成す角部B(図4参照)の曲率半径を、微細輪郭形状測定器を用いて測定した。曲率半径は、基板1枚あたり表裏1点ずつ合計2点を測定し、その平均値をその基板の測定値とした。これを基板100枚について繰り返し、バラツキ(最大値と最小値の差)を算出した。その結果について以下の4段階の相対評価を行い、表1に示した。◎、○、△であれば実用上合格である。
◎:優れている(バラツキが0.015mm以下)
○:良好(バラツキが0.025mm以下)
△:一応合格(バラツキが0.045mm以下)
×:不合格(バラツキが0.045mmより大)
また、面取り面の表面粗さRaを、レーザー顕微鏡による測定値を元に算出し、その結果についても表1に示した。
また、上記精密研削時における研削速度についても表1に示した。 As described above, the inner peripheral side end faces of 100 glass substrates were ground.
In order to confirm the shape and dimensional accuracy of the side wall surface and the chamfered surface of the inner peripheral side end surface of the obtained 100 glass substrates, the corner portion A formed by the side wall surface and the chamfered surface and the main surface and the chamfered surface The radius of curvature of the corner B (see FIG. 4) was measured using a fine contour shape measuring instrument. As for the radius of curvature, a total of two points were measured, one on each side of the substrate, and the average value was taken as the measured value of the substrate. This was repeated for 100 substrates, and the variation (difference between the maximum value and the minimum value) was calculated. The results were evaluated in the following four stages and are shown in Table 1. ◎, ○, and Δ are practically acceptable.
A: Excellent (variation is 0.015 mm or less)
○: Good (variation is 0.025 mm or less)
Δ: Passed (variation is 0.045 mm or less)
X: Fail (the variation is larger than 0.045 mm)
Further, the surface roughness Ra of the chamfered surface was calculated based on the measured value with a laser microscope, and the results are also shown in Table 1.
Table 1 also shows the grinding speed during the precision grinding.
これに対し、ナノインデンテーション試験法によって測定される硬度が、0.4GPa未満である比較例1の研削砥石を用いると、端面品質及び研削速度の両方について良好な結果が得られなかった。つまり、硬度の低すぎる領域では砥粒の保持強度が低く、加工中に砥粒の脱落が促進されて目こぼれ状態となり、そのため研削速度が得られず、形状だれが発生して端面品質も悪化している状態と考えられる。
また、ナノインデンテーション試験法によって測定される硬度が、1.7GPaよりも大きい比較例2、3の研削砥石を用いると、砥粒の保持強度が大きすぎて砥粒の脱落による自生発刃作用が進まず、研削屑が砥石表面に堆積する目詰まりや砥粒の摩滅による目つぶれが発生することで、研削速度が得られず、加工面にはヤケによる品質劣化が発生している状態と考えられる。
また、以上の結果から、研削砥石の研削性能を評価する上で、ナノインデンテーション試験法によって測定される硬度を指標とすることが最適であることが確認できた。 As is clear from the results in Table 1 above, the inner circumference side of the substrate using the grinding stones of Examples 1 to 7 whose hardness measured by the nanoindentation test method is in the range of 0.4 to 1.7 GPa. When precision grinding of the end face was performed, good results were obtained in the end face roughness, end shape and dimensional accuracy. The grinding speed was also good.
In contrast, when the grinding wheel of Comparative Example 1 having a hardness measured by the nanoindentation test method of less than 0.4 GPa was used, good results were not obtained for both the end face quality and the grinding speed. In other words, in areas where the hardness is too low, the holding strength of the abrasive grains is low, and the falling of the abrasive grains is promoted during processing, resulting in a spilled state. It is thought that it is in a state.
In addition, when the grinding wheels of Comparative Examples 2 and 3 having a hardness measured by the nanoindentation test method of greater than 1.7 GPa are used, the holding strength of the abrasive grains is too high and the self-generated blade action due to the falling off of the abrasive grains. The crushing due to clogging of grinding scraps accumulated on the surface of the grindstone or the abrasion of abrasive grains occurs, the grinding speed cannot be obtained, and the processed surface has deteriorated quality due to burns. Conceivable.
In addition, from the above results, it was confirmed that the hardness measured by the nanoindentation test method is the optimum for evaluating the grinding performance of the grinding wheel.
上記の精密研削加工用に、ダイヤモンド砥粒と、ダイヤモンド砥粒同士を結合するバインダーがフェノール樹脂であるレジンボンド砥石であって、ナノインデンテーション試験法により測定した硬度が1.3GPaであり、平均粒径が1.5~25μmの範囲内で異なる6種類の砥石を準備した。
以上の砥石を用いたこと以外は、実施例1と同様にしてガラス基板の内周側端面の研削加工を行い、得られたガラス基板について実施例1と同様の評価を行い、その結果を表2に示した。 (Examples 8 to 13)
For the above precision grinding process, diamond abrasive grains and a resin bond grindstone in which the binder for bonding the diamond abrasive grains is a phenol resin, the hardness measured by the nanoindentation test method is 1.3 GPa, and the average Six types of grindstones with different particle sizes in the range of 1.5 to 25 μm were prepared.
Except that the above grindstone was used, the inner peripheral side end face of the glass substrate was ground in the same manner as in Example 1, the obtained glass substrate was evaluated in the same manner as in Example 1, and the results are shown. It was shown in 2.
また、実施例8~13と同じ仕様の砥石を用いて、外径端部の精密研削加工を行ったところ、ガラス基板を傾斜させる、させない、また、外接型加工(図1、図2参照)、内接型加工(図7参照)に関わらず、表2と同様に砥粒の平均粒径が2μm~15μmの範囲内であると、端面粗さと、端部形状・寸法精度において特に良好な結果が得られた。 As is apparent from the results in Table 2 above, even with a grindstone having the same hardness, when the average grain size of the abrasive grains is in the range of 2 μm to 15 μm, particularly good results are obtained in the end face roughness and the end shape / dimensional accuracy. This is advantageous. When the average particle size was 1.5 μm, slight grinding marks were observed on the surface.
In addition, when a grinding wheel having the same specifications as in Examples 8 to 13 was used, precision grinding of the outer diameter end portion was performed, and the glass substrate was not tilted or circumscribed (see FIGS. 1 and 2). Regardless of the inscribed type machining (see FIG. 7), the average grain size of the abrasive grains is in the range of 2 μm to 15 μm, as in Table 2, and the end face roughness and the end shape / dimensional accuracy are particularly good. Results were obtained.
まず、前述の実施例と同様にして、溶融ガラスから上型、下型、胴型を用いたダイレクトプレスにより直径66mmφの円盤状のアルミノシリケートガラスからなるガラス基板(ガラスディスク)を得た。次いで、ガラス基板に寸法精度及び形状精度を向上させるためラッピング工程を行った。 (Examples 101 to 103, Comparative Examples 101 and 102)
First, a glass substrate (glass disk) made of disc-shaped aluminosilicate glass having a diameter of 66 mmφ was obtained from molten glass by direct pressing using an upper die, a lower die, and a barrel die in the same manner as in the above-described example. Next, a lapping process was performed on the glass substrate in order to improve dimensional accuracy and shape accuracy.
上記の粗研削加工にはダイヤモンド砥粒を電着ボンドで固めた電着ボンド砥石を使用した。また、上記の精密研削加工には、平均砥粒径が5μmのダイヤモンド砥粒と、バインダーとしてフェノール樹脂とを含むレジンボンド砥石を使用した。このレジンボンド砥石は、構成材料は同じであるが、バインダー部分の硬度の異なる10種類の砥石を準備した。砥石のバインダー部分の硬度は、上述のナノインデンテーション試験法により測定した。 Next, a hole is made in the central portion of the glass substrate using a cylindrical grindstone, and the end surface is roughly ground by a machining method using the general grindstone as shown in FIG. Precision grinding is performed by a method in which the grindstone is brought into contact with the glass substrate as shown in FIG.
An electrodeposition bond grindstone in which diamond abrasive grains are hardened with an electrodeposition bond was used for the above rough grinding. In the precision grinding, a resin bond grindstone containing diamond abrasive grains having an average abrasive grain size of 5 μm and a phenol resin as a binder was used. This resin-bonded grindstone has the same constituent material, but 10 types of grindstones with different binder part hardness were prepared. The hardness of the binder part of the grindstone was measured by the nanoindentation test method described above.
得られた100枚のガラス基板について、前述の実施例と同様にして、端面の側壁面と面取り面の形状・寸法精度の評価を行い、その結果を表3に示した。また、面取り面の表面粗さRa、及び研削速度についても、その結果を表3に示した。 As described above, end grinding of the glass substrate was performed to produce 100 glass substrates.
For the 100 glass substrates obtained, the shape and dimensional accuracy of the side wall surface and chamfered surface of the end surface were evaluated in the same manner as in the above-described example, and the results are shown in Table 3. The results of the chamfered surface roughness Ra and the grinding speed are shown in Table 3.
これに対し、最適範囲よりも硬度の低い領域から選択した研削砥石を用いると(比較例101)、研削速度において良好な結果は得られなかった。そして、端面粗さ、端部形状・寸法精度においても良好な結果は得られなかった。つまり、硬度の低い領域では砥粒の保持強度が低く、加工中に砥粒の脱落が促進されて目こぼれ状態となり、そのため研削速度が得られず、形状だれが発生して端面品質も悪化している状態と考えられる。
また、最適範囲よりも硬度の高い領域から選択した研削砥石を用いたところ(比較例102)、良好な研削速度は得られなかった。そして、端面粗さ、端部形状・寸法精度においても良好な結果は得られなかった。この場合、砥粒の保持強度が大きすぎて砥粒の脱落による自生発刃作用が進まず、研削屑が砥石表面に堆積する目詰まりや砥粒の磨滅による目つぶれが発生することで、研削速度が得られず、加工面にもヤケによる品質劣化が発生している状態と考えられる。
以上の結果から、研削砥石の研削性能を評価する上で、ナノインデンテーション試験法によって測定される硬度と、この研削砥石を用いて、ある条件でガラス基板端面を研削処理したときの研削速度との相関関係を予め求めておき、求められた相関関係に基づき研削砥石を選択することが最適であることが確認できた。 As is clear from the results in Table 3 above, when the substrate end face is precisely ground using a grinding wheel selected from the optimum range based on the correlation shown in FIG. 6 (Examples 101 to 103), a good grinding speed is obtained. Obtained. Also, good results were obtained in terms of end surface roughness, end shape and dimensional accuracy.
On the other hand, when a grinding wheel selected from a region having a hardness lower than the optimum range was used (Comparative Example 101), good results were not obtained at the grinding speed. Also, good results were not obtained in terms of end surface roughness, end shape and dimensional accuracy. In other words, in the low hardness region, the holding strength of the abrasive grains is low, and the falling of the abrasive grains is promoted during processing, resulting in a spilled state. It is thought that it is in a state.
Further, when a grinding wheel selected from a region having a hardness higher than the optimum range was used (Comparative Example 102), a good grinding speed could not be obtained. Also, good results were not obtained in terms of end surface roughness, end shape and dimensional accuracy. In this case, the holding strength of the abrasive grains is too high, and the self-generated blade action does not advance due to the falling off of the abrasive grains. The speed is not obtained, and it is considered that quality degradation due to burn has occurred on the processed surface.
From the above results, in evaluating the grinding performance of the grinding wheel, the hardness measured by the nanoindentation test method, and the grinding speed when the end surface of the glass substrate is ground under certain conditions using this grinding wheel. It has been confirmed that it is optimal to obtain the correlation of the above in advance and select a grinding wheel based on the obtained correlation.
前述の実施例と同様にして、溶融ガラスから上型、下型、胴型を用いたダイレクトプレスにより直径66mmφの円盤状のアルミノシリケートガラスからなるガラス基板(ガラスディスク)を得た。次いで、ガラス基板に寸法精度及び形状精度を向上させるためラッピング工程を行った。
次に、円筒状の砥石を用いてガラス基板の中央部分に孔を空けると共に、前述の図1に示すような総形砥石を用いた加工法により外周端面の粗研削加工を行い、続いて、以下に説明する方法により精密研削加工を行った。
上記の粗研削加工にはダイヤモンド砥粒を電着ボンドで固めた電着ボンド砥石を使用した。また、上記の精密研削加工には、平均砥粒径が5μmのダイヤモンド砥粒と、バインダーとしてフェノール樹脂とを含むレジンボンド砥石を使用した。このレジンボンド砥石は、構成材料は同じであるが、バインダー部分の硬度の異なる5種類の砥石を準備した。砥石のバインダー部分の硬度は、上述のナノインデンテーション試験法により測定した。 (Examples 201 to 212, Comparative examples 201 to 208)
In the same manner as in the previous examples, a glass substrate (glass disk) made of disc-shaped aluminosilicate glass having a diameter of 66 mmφ was obtained from molten glass by direct pressing using an upper die, a lower die, and a barrel die. Next, a lapping process was performed on the glass substrate in order to improve dimensional accuracy and shape accuracy.
Next, a cylindrical grindstone is used to make a hole in the central portion of the glass substrate, and the outer peripheral end face is roughly ground by a processing method using the overall grindstone as shown in FIG. Precision grinding was performed by the method described below.
An electrodeposition bond grindstone in which diamond abrasive grains are hardened with an electrodeposition bond was used for the above rough grinding. In the precision grinding, a resin bond grindstone containing diamond abrasive grains having an average abrasive grain size of 5 μm and a phenol resin as a binder was used. This resin-bonded grindstone has the same constituent material, but five types of grindstones having different binder part hardnesses were prepared. The hardness of the binder part of the grindstone was measured by the nanoindentation test method described above.
第1の方法は、前述の図1に示すガラス基板と砥石との配置関係で行った(表4中には「外接(図1)」と表記した。)
第2の方法は、前述の図7に示すガラス基板と砥石との配置関係で行い、ガラス基板に対する砥石の傾き角度は0度(つまり傾斜なし)とした(表4中には「内接」と表記した。)。
第3の方法は、前述の図2に示すガラス基板と砥石との配置関係で行い、ガラス基板に対する砥石の傾き角度αは10度に設定した(表4中には「外接・傾斜(図2)」と表記した。)。
第4の方法は、前述の図7に示すガラス基板と砥石との配置関係で行い、ガラス基板に対する砥石の傾き角度αは10度に設定した(表4中には「内接・傾斜(図7)」と表記した。)。
なお、ガラス基板と砥石の各々の周速度、回転方向、加工圧は適宜設定して行った。 Each of these five types of grinding wheels was used to precisely grind the outer peripheral end face of the substrate. The precision grinding process was performed in the following four ways.
The first method was performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 1 described above (indicated as “external circumstance (FIG. 1)” in Table 4).
The second method is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 7 described above, and the inclination angle of the grindstone with respect to the glass substrate is 0 degree (that is, there is no inclination) (“Inscribed” in Table 4). .)
The third method is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 2 described above, and the inclination angle α of the grindstone with respect to the glass substrate is set to 10 degrees (in Table 4, “circumscribed / inclined (FIG. 2 ) ").
The fourth method is performed by the positional relationship between the glass substrate and the grindstone shown in FIG. 7, and the inclination angle α of the grindstone with respect to the glass substrate is set to 10 degrees (in Table 4, “inscribed / inclined (figure 7) ”).
Note that the peripheral speed, rotation direction, and processing pressure of each of the glass substrate and the grindstone were set appropriately.
得られた100枚のガラス基板について、前述の実施例と同様にして、外周端面の側壁面と面取り面の形状・寸法精度の評価を行い、その結果を表4に示した。また、面取り面の表面粗さRa、及び研削速度についても、その結果を表4に示した。 As described above, precision grinding of the outer peripheral end face of the substrate was performed by combining the above five types of grinding wheels and the above-described four processing methods, and 100 glass substrates were manufactured.
For the 100 glass substrates obtained, the shape and dimensional accuracy of the side wall surface and the chamfered surface of the outer peripheral end surface were evaluated in the same manner as in the above-described example, and the results are shown in Table 4. The results of the chamfered surface roughness Ra and the grinding speed are shown in Table 4.
特に端面粗さについていえば、前述の図1に示すガラス基板と砥石との配置関係(外接)よりも、前述の図7に示すようなガラス基板と砥石との配置関係(内接、但し傾斜なし)により加工を行うほうがより好ましい結果が得られた。また、前述の図2や図7のように、ガラス基板に対して砥石を傾斜させて加工を行うほうがより好ましい結果が得られた。
これに対し、ナノインデンテーション試験法によって測定される硬度が、0.4GPa未満あるいは1.7GPaよりも大きい研削砥石を用いると、いずれの加工方法を適用しても、端面品質及び研削速度の両方について良好な結果が得られなかった。 As is clear from the results of Table 4 above, when the substrate outer peripheral end face is precisely ground using a grinding wheel whose hardness measured by the nanoindentation test method is in the range of 0.4 to 1.7 GPa, In any of the processing methods, good results were obtained in end surface roughness, end shape and dimensional accuracy. The grinding speed was also good.
In particular, with regard to the end surface roughness, the positional relationship between the glass substrate and the grindstone as shown in FIG. 7 (inscribed, but inclined) rather than the positional relationship between the glass substrate and the grindstone as shown in FIG. More preferable results were obtained when processing was carried out. In addition, as shown in FIG. 2 and FIG. 7 described above, it was more preferable to perform the processing by inclining the grindstone with respect to the glass substrate.
In contrast, when a grinding wheel having a hardness measured by the nanoindentation test method of less than 0.4 GPa or greater than 1.7 GPa is used, both the end face quality and the grinding speed are applied regardless of which processing method is applied. Good results were not obtained.
2,7 外周側端面研削砥石
3,8 内周側端面研削砥石
6 溝
1a ガラス基板の主表面
1b 側壁面
1c 面取り面
DESCRIPTION OF
Claims (9)
- 中心に円孔を有する円盤状のガラス基板の端面を研削するための研削砥石であって、
前記研削砥石は、砥粒と、当該砥粒同士を結合するバインダーとを含み、
前記研削砥石表面のバインダー部分を、バーコビッチ圧子を用いて、250mNの押込み荷重の条件でナノインデンテーション試験法によって測定される硬度が、0.4~1.7GPaの範囲内であることを特徴とする研削砥石。 A grinding wheel for grinding an end face of a disk-shaped glass substrate having a circular hole in the center,
The grinding wheel includes abrasive grains and a binder that bonds the abrasive grains together,
The hardness measured by the nanoindentation test method in the condition of an indentation load of 250 mN using a Berkovich indenter on the binder portion of the grinding wheel surface is in the range of 0.4 to 1.7 GPa. To grindstone. - 前記砥粒の平均粒子径は、2~15μmの範囲内であることを特徴とする請求項1に記載の研削砥石。 2. The grinding wheel according to claim 1, wherein an average particle diameter of the abrasive grains is in a range of 2 to 15 μm.
- 前記研削砥石は、前記ガラス基板の主表面と直交する軸に対して砥石の回転軸を傾斜させた状態で当該砥石を前記ガラス基板の端面に当接させて当該ガラス基板の端面を研削処理する際に用いる回転砥石であることを特徴とする請求項1又は2に記載の研削砥石。 The grinding wheel grinds the end surface of the glass substrate by bringing the grindstone into contact with the end surface of the glass substrate in a state where the rotation axis of the grindstone is inclined with respect to an axis orthogonal to the main surface of the glass substrate. The grinding wheel according to claim 1, wherein the grinding wheel is a rotary grindstone used at the time.
- 請求項1乃至3のいずれかに記載の研削砥石を用いて、前記ガラス基板の端面の研削処理を行う工程を含むことを特徴とする磁気ディスク用ガラス基板の製造方法。 A method for producing a glass substrate for a magnetic disk, comprising a step of grinding an end face of the glass substrate using the grinding wheel according to any one of claims 1 to 3.
- 中心に円孔を有する円盤状のガラス基板の端面を研削砥石を用いて研削する研削処理を含む磁気ディスク用ガラス基板の製造方法であって、
前記研削砥石は、砥粒と、当該砥粒同士を結合するバインダーとを含み、
前記研削砥石表面のバインダー部分を、バーコビッチ圧子を用いて、250mNの押込み荷重の条件でナノインデンテーション試験法によって測定される硬度と、当該研削砥石を用いてガラス基板端面を研削処理したときの研削速度との相関関係を予め求めておき、
求められた相関関係に基づき、所望の研削速度となるような硬度を有する研削砥石を選択し、この選択された研削砥石を用いて前記研削処理を行うことを特徴とする磁気ディスク用ガラス基板の製造方法。 A method of manufacturing a glass substrate for a magnetic disk including a grinding process of grinding an end face of a disk-shaped glass substrate having a circular hole in the center using a grinding wheel,
The grinding wheel includes abrasive grains and a binder that bonds the abrasive grains together,
Grinding the binder part on the surface of the grinding wheel using a Berkovich indenter and the hardness measured by the nanoindentation test method under the condition of an indentation load of 250 mN, and grinding the glass substrate end surface using the grinding wheel Find the correlation with speed in advance,
A glass substrate for a magnetic disk comprising: selecting a grinding wheel having a hardness that provides a desired grinding speed based on the obtained correlation, and performing the grinding process using the selected grinding wheel. Production method. - 前記研削砥石は、前記バインダーが樹脂材料からなり、前記ナノインデンテーション試験法によって測定される硬度が、0.4~1.7GPaの範囲内であることを特徴とする請求項5に記載の磁気ディスク用ガラス基板の製造方法。 The magnetic grinding wheel according to claim 5, wherein the grinding wheel has a binder made of a resin material, and has a hardness measured by the nanoindentation test method in a range of 0.4 to 1.7 GPa. A method for producing a glass substrate for a disk.
- 前記選択された研削砥石を用いて、前記ガラス基板の主表面と直交する軸に対して当該研削砥石の回転軸を傾斜させた状態で当該研削砥石を前記ガラス基板の端面に当接させて当該ガラス基板の端面を研削処理することを特徴とする請求項5又は6に記載の磁気ディスク用ガラス基板の製造方法。 Using the selected grinding wheel, the grinding wheel is brought into contact with the end surface of the glass substrate in a state where the rotation axis of the grinding wheel is inclined with respect to an axis orthogonal to the main surface of the glass substrate. The method for producing a glass substrate for a magnetic disk according to claim 5 or 6, wherein an end surface of the glass substrate is ground.
- 前記ガラス基板の端面の表面粗さRaが、0.1μm以下になるように研削処理することを特徴とする請求項4乃至7のいずれかに記載の磁気ディスク用ガラス基板の製造方法。 The method for producing a glass substrate for a magnetic disk according to any one of claims 4 to 7, wherein the glass substrate is ground so that the surface roughness Ra of the end surface of the glass substrate is 0.1 µm or less.
- 請求項4乃至8のいずれかに記載の磁気ディスク用ガラス基板の製造方法によって製造された磁気ディスク用ガラス基板の主表面上に少なくとも磁性層を形成することを特徴とする磁気ディスクの製造方法。
A method for manufacturing a magnetic disk, comprising forming at least a magnetic layer on a main surface of the glass substrate for a magnetic disk manufactured by the method for manufacturing a glass substrate for a magnetic disk according to claim 4.
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