JP6299369B2 - Manufacturing method of plate-like body - Google Patents

Description

  The present invention relates to a method for producing a plate-like body and a rubber grindstone.

  A method for producing a plate-like body such as a glass substrate for a magnetic recording medium includes a chamfering process for forming a chamfered portion and a side surface portion on an end surface of the plate-like body, and an end surface polishing for polishing the chamfered portion and the side surface portion with a rotating brush. (For example, refer patent document 1). The side surface portion of the plate-like body may be perpendicular to the main surface of the plate-like body.

JP 2010-238302 A

  In the end surface polishing step, the chamfered portion and the side surface portion are polished with a rotating brush while supplying the polishing liquid, thereby removing the work-affected layer on the chamfered portion and the side surface portion. The work-affected layer is a layer containing scratches and cracks generated in the chamfering process.

  The rotating brush is composed of a rotating shaft perpendicular to the main surface of the plate-like body and brush hairs attached to the outer periphery of the rotating shaft. The rotating brush polishes the end surface of the plate-like body with brush bristles while rotating around the rotation axis. A polishing liquid is supplied to the polishing portion by the rotating brush.

  Compared to the side surface of the plate-like body, the chamfered portion of the plate-like body is far from the rotation axis of the rotary brush and is a part where the brush hair is difficult to reach. It is hard to be polished. Of the chamfered portion of the plate-like body, the vicinity of the boundary with the main surface of the plate-like body is a portion where the brush hair and the abrasive are particularly difficult to reach and are not easily polished. This problem is remarkable when a plurality of plate-like bodies are laminated and subjected to brush polishing.

  If it is attempted to remove the work-affected layer in the chamfered portion in the end surface polishing step, the machining allowance of the side surface portion is large, and the shape of the plate-like body is destroyed. For example, in the case of a disk-shaped glass substrate for a magnetic recording medium having a circular hole in the center, roundness and concentricity deteriorate.

  The present invention has been made in view of the above problems, and mainly provides a method for producing a plate-like body, which can remove a work-affected layer generated in a chamfering step and can suppress the deformation of the plate-like body. With a purpose.

In order to solve the above problems, according to one aspect of the present invention,
A chamfering step of forming a chamfered portion and a side portion on the end face of the plate-like body and a first major surface and a second major surface and the end face, the end face is polished by a rotating brush the chamfered portion and the side portions A method for producing a plate-like body, comprising a polishing step,
After the chamfering step, before the end face polishing step, it has a chamfered portion processing step of processing the chamfered portion with a rubber grindstone,
The chamfered portion has a first chamfered portion on the first main surface side and a second chamfered portion on the second main surface side,
The rubber grindstone has a plurality of abrasive grains and a rubber that binds the plurality of abrasive grains, and has a first processing surface and a second processing surface that come into contact with the plate-like body,
In the chamfered portion processing step, the first processed surface and the second processed surface so that the first processed surface is in contact with the first chamfered portion and the second processed surface is in contact with the second chamfered portion. the plate-like body is inserted, said second working surface and said first work surface and the second processing surface and the side surface portion and the first processing surface before SL such that a space is formed which is surrounded by between And manufacturing the plate-like body by expanding the gap formed between the first processed surface and processing the first chamfered portion on the first processed surface and processing the second chamfered portion on the second processed surface. Is provided.

  According to one aspect of the present invention, there is provided a method for producing a plate-like body, which can remove a work-affected layer generated in a chamfering step and can suppress the deformation of the plate-like body.

It is a flowchart which shows the manufacturing method of the glass substrate for magnetic recording media by one Embodiment of this invention. It is a figure which shows the state before the contact with the chamfering grindstone and plate-shaped object by one Embodiment of this invention. It is a figure which shows the state at the time of contact with the chamfering grindstone and plate-shaped object by one Embodiment of this invention. It is a figure which shows the state after contact with the chamfering grindstone by one Embodiment of this invention, and a plate-shaped object. It is a figure which shows the state before the contact with the rubber grindstone by one Embodiment of this invention, and a plate-shaped object. It is a figure which shows the state at the time of the contact with the rubber grindstone by one Embodiment of this invention, and a plate-shaped object. It is a figure which shows the state at the time of contact with the rotating brush and plate-shaped object by one Embodiment of this invention. It is a figure which shows the grindstone unit containing the chamfering grindstone and rubber grindstone by one Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted. In this specification, “to” representing a numerical range means a range including numerical values before and after the numerical range.

  Hereinafter, although the manufacturing method of the glass substrate for magnetic recording media as a plate-shaped object is demonstrated, the kind of plate-shaped object may be various, and uses other than the object for magnetic recording media (For example, for flat panel displays and for buildings) Glass plate, ceramic plate, silicon wafer or the like. The plate-like body may be a laminated plate, and may include, for example, a metal film, a resin film, or the like between glass plates.

  FIG. 1 is a flowchart showing a method for manufacturing a glass substrate for a magnetic recording medium according to an embodiment of the present invention. The glass substrate for magnetic recording media has a disc shape and has a circular hole in the center. A magnetic recording medium can be obtained by forming a magnetic layer or the like on a glass substrate for a magnetic recording medium.

  As shown in FIG. 1, the manufacturing method of the glass substrate for magnetic recording media includes a base plate processing step (step S11), a chamfering step (step S12), a chamfered portion processing step (step S13), and an end surface polishing step (step). S14), and a main surface polishing step (step S15). An etching process, a cleaning process, a drying process, etc. may be performed between these processes or after these processes.

  In the base plate processing step (step S11), a disk-shaped glass substrate having a circular hole in the center is obtained by processing the glass base plate. The glass base plate is formed by, for example, a float method, a fusion method, a press forming method, a down draw method, a redraw method, or the like.

  The chamfering step (step S12) forms a chamfered portion and a side surface portion on the end surface of the glass substrate by grinding the end surface (the inner peripheral end surface and the outer peripheral end surface) of the glass substrate with a chamfering grindstone. The chamfered portion may be inclined with respect to the main surface of the glass substrate, and the side surface portion may be perpendicular to the main surface of the glass substrate. Note that the chamfered portion may not be a flat surface, and may be a rounded curved surface.

  The chamfered portion machining step (step S13) reduces the thickness of the work-affected layer in the chamfered portion by processing the chamfered portion with a rubber grindstone. The work-affected layer is a layer containing scratches and cracks generated in the chamfering process. The work-affected layer is formed on the chamfered portion and the side surface portion.

  The end surface polishing step (step S14) removes the work-affected layer in the chamfered portion and the side surface portion by polishing the chamfered portion and the side surface portion with a rotating brush while supplying the polishing liquid. A polishing liquid is supplied to the polishing portion by the rotating brush.

  Note that a plurality of end surface polishing steps may be sequentially performed, and the work-affected layer may not be removed with a rotating brush alone. In addition to brush polishing with a rotating brush, sponge polishing, viscous fluid polishing, magnetic fluid polishing, and the like may be performed. A cleaning process and a drying process may be performed between the plurality of end face polishing processes.

  In the main surface polishing step (step S15), the main surfaces (first main surface and second main surface) of the glass substrate are polished. In the main surface polishing step, a double-side polishing machine that simultaneously polishes the first main surface and the second main surface of the glass substrate may be used. The double-side polishing machine may polish a plurality of glass substrates simultaneously.

  A plurality of main surface polishing steps may be performed sequentially. The plurality of main surface polishing steps are performed by changing the type of polishing pad and the particle size of the abrasive grains contained in the polishing liquid. A cleaning process and a drying process may be performed between the plurality of main surface polishing processes.

  In addition, the order of each process shown in FIG. 1 is not specifically limited. For example, the end surface polishing step (step S14) may be performed after the main surface polishing step (step S15). Moreover, processes other than the process shown in FIG. 1 may be performed. For example, the main surface of the glass substrate may be lapped (for example, free abrasive wrap, fixed abrasive wrap) before the main surface polishing step. Further, chemical strengthening may be performed between the main surface polishing step after the end surface polishing step and the main surface polishing step. Chemical strengthening replaces ions with a small ion radius (for example, Li ions and Na ions) contained on the surface of a glass plate with ions with a large ion radius (for example, K ions) to form a strengthened layer with a predetermined depth from the surface. To do. Since the compressive stress remains in the reinforcing layer, it is difficult to be damaged.

  Next, the chamfering process will be described with reference to FIGS. FIG. 2 is a view showing a state before contact between the chamfering grindstone and the plate-like body according to the embodiment of the present invention. FIG. 3 is a diagram showing a state at the time of contact between the chamfering grindstone and the plate-like body according to the embodiment of the present invention. FIG. 4 is a view showing a state after contact between the chamfering grindstone and the plate-like body according to the embodiment of the present invention.

  In the chamfering step, the first chamfered portion 11, the second chamfered portion 12, and the side surface portion 13 are formed on the inner peripheral end surface by grinding the inner peripheral end surface of the glass substrate 10 with the chamfering grindstone 20. In addition, since the method of grinding the outer peripheral end surface of the glass substrate 10 and forming a chamfered part and a side part in the outer peripheral end surface is the same, description is abbreviate | omitted.

  The chamfering grindstone 20 may include a plurality of abrasive grains and a metal that bonds the plurality of abrasive grains. As the abrasive grains, diamond abrasive grains, cubic boron nitride (CBN) abrasive grains, alumina abrasive grains, silicon carbide abrasive grains and the like are used. The chamfering grindstone 20 may be an electrodeposition grindstone that fixes abrasive grains by plating. The chamfering grindstone 20 may be a metal bond grindstone formed by sintering abrasive grains or metal powder.

  The chamfering grindstone 20 grinds the inner peripheral end surface of the glass substrate 10 while rotating around the center line of the chamfering grindstone 20. The glass substrate 10 may be rotated around the center line of the glass substrate 10 when grinding with the chamfering grindstone 20. The center line of the chamfering grindstone 20 and the center line of the glass substrate 10 are parallel.

  The chamfering grindstone 20 has an annular grinding groove 21 on the outer periphery of the chamfering grindstone 20, and the first chamfered portion 11, the second chamfering grindstone 20 by grinding the inner peripheral end surface of the glass substrate 10 with the wall surface of the grinding groove 21. A chamfered portion 12 and a side surface portion 13 are formed. The cross-sectional shape of the grinding groove 21 is an isosceles trapezoid. The first chamfered portion 11 is connected to the first main surface 15 at an angle, and the second chamfered portion 12 is connected to the second main surface 16 at an angle. The side surface portion 13 is formed between the first chamfered portion 11 and the second chamfered portion 12 and may be perpendicular to the first main surface 15 and the second main surface 16.

  In the present embodiment, in the chamfering step, the first chamfered portion 11 and the second chamfered portion 12 are formed on the inner peripheral end surface of the glass substrate 10, but the number of chamfered portions may be one, The side surface portion 13 may be connected perpendicularly to the first main surface 15 or the second main surface 16. The same applies to the outer peripheral end face of the glass substrate 10.

  Next, for the sake of explanation, the end surface polishing step will be described with reference to FIG. The chamfered portion processing step performed before the end surface polishing step will be described later.

  In the end surface polishing step, the inner peripheral end surface of the glass substrate 10 is polished with the rotating brush 40. In addition, since the method of grind | polishing the chamfered part and side part formed in the outer peripheral end surface of the glass substrate 10 is the same, description is abbreviate | omitted.

  The rotating brush 40 has a rotating shaft 41 perpendicular to the first main surface 15 and the second main surface 16 of the glass substrate 10, and brush hairs 42 attached to the outer periphery of the rotating shaft 41. The rotating brush 40 polishes the first chamfered portion 11, the second chamfered portion 12, and the side surface portion 13 with the brush bristles 42 while rotating around the rotating shaft 41.

  A polishing liquid is supplied from the nozzle to the polishing portion of the glass substrate 10 by the rotating brush 40. The polishing liquid contains an abrasive, and for example, cerium oxide abrasive grains are used as the abrasive.

  In the end surface polishing step, a plurality of glass substrates 10 may be laminated and polished together. In this case, a spacer may be disposed between the glass substrates 10. The rotating brush 40 is swung in the stacking direction of the glass substrates 10 (direction parallel to the center line of the rotating shaft 41) while being rotated about the center line of the rotating shaft 41.

  Compared to the side surface portion 13 of the glass substrate 10, the first chamfered portion 11 and the second chamfered portion 12 of the glass substrate 10 are far from the rotation shaft 41 of the rotating brush 40 and are not easily polished by the brush bristles 42. In particular, the vicinity of the boundary 17 between the first chamfered portion 11 and the first main surface 15 in the first chamfered portion 11, and the second chamfered portion 12 and the second main surface 16 in the second chamfered portion 12. The vicinity of the boundary 18 is far from the rotation shaft 41 of the rotary brush 40 and is not easily polished by the brush bristles 42. Therefore, the polishing amount of the first chamfered portion 11 and the second chamfered portion 12 is smaller than the polishing amount of the side surface portion 13.

  Therefore, in this embodiment, the chamfered portion processing step is performed after the chamfering step and before the end surface polishing step. Hereinafter, the chamfered portion machining step will be described with reference to FIGS. FIG. 5 is a view showing a state before contact between the rubber grindstone and the plate-like body according to the embodiment of the present invention. FIG. 6 is a view showing a state at the time of contact between the rubber grindstone and the plate-like body according to the embodiment of the present invention.

  In the chamfered portion processing step, the first chamfered portion 11 and the second chamfered portion 12 formed on the inner peripheral end surface of the glass substrate 10 are processed by the rubber grindstone 30 after the chamfering step and before the end surface polishing step. To do. In addition, since the method of processing the chamfered part formed in the outer peripheral end surface of the glass substrate 10 is the same, description is abbreviate | omitted.

  In the end surface polishing step, the polishing amount of the first chamfered portion 11 and the second chamfered portion 12 is smaller than the polished amount of the side surface portion 13 as described above. Therefore, the thickness of the work-affected layer in the first chamfered portion 11 and the second chamfered portion 12 is reduced by the chamfered portion machining step before the end surface polishing step. Thereby, the work-affected layer can be removed from the first chamfered portion 11, the second chamfered portion 12, and the side surface portion 13 while suppressing the shape collapse of the glass substrate 10. Further, the time for the end face polishing step is short, and the productivity is good. Since the time of the end surface polishing process is short, the wear of the rotating brush 40 can be suppressed.

  Unlike the outer peripheral end surface of the glass substrate 10, the inner peripheral end surface of the glass substrate 10 may be held by a rotary chuck or the like. According to this embodiment, since the shape collapse of the inner peripheral end surface of the glass substrate 10 can be suppressed, the accuracy of the inner peripheral end surface as the rotation reference surface is good. Moreover, according to this embodiment, since the work-affected layer on the inner peripheral end face of the glass substrate 10 can be removed, the glass substrate 10 can be prevented from cracking due to chucking.

  In the chamfered part process, the work-affected layer in the first chamfered part 11 and the second chamfered part 12 may not be completely removed or may be completely removed. In the chamfering step, the first chamfered portion 11 and the second chamfered portion 12 need only be more easily polished than the side surface portion 13, and the side surface portion 13 may also be polished.

  The rubber grindstone 30 has a plurality of abrasive grains and rubber that binds the plurality of abrasive grains. The rubber grindstone 30 has a first processed surface 31 that contacts the first chamfered portion 11 and a second processed surface 32 that contacts the second chamfered portion 12. The rubber grindstone 30 may have a plurality of sets of the first processed surface 31 and the second processed surface 32.

  In the chamfered portion machining step, the glass substrate 10 is inserted between the first machining surface 31 and the second machining surface 32 to form a gap 33 formed between the first machining surface 31 and the second machining surface 32. The first chamfered portion 11 is processed with the first processed surface 31 and the second chamfered portion 12 is processed with the second processed surface 32. According to this method, the first chamfered portion 11 and the second chamfered portion 12 are more easily polished than the side surface portion 13. Further, according to this method, when the rubber grindstone 30 is worn, the first chamfered portion 11 is processed by the first processed surface 31 and the second processed surface 32 by inserting the glass substrate 10 deeper. Thus, the second chamfered portion 12 can be processed. Therefore, it can be used for a long time.

  In addition, when using a resin bond grindstone instead of the rubber grindstone 30, long-time use is difficult. Since the resin bond grindstone includes a thermosetting resin as a binder, it hardly deforms elastically unlike a rubber grindstone. An annular grinding groove is formed on the outer periphery of the resin bond grindstone, and the cross-sectional shape of the grinding groove is an isosceles trapezoid. The end surface of the glass substrate is polished to the cross-sectional shape of the wall surface of the grinding groove. Therefore, when the cross-sectional shape of the wall surface of the grinding groove is broken due to wear, it is difficult to process the end surface of the glass substrate into a target shape, and it is difficult to use the glass substrate for a long time.

  Before the glass substrate 10 is inserted, the gap 33 may be continuously narrowed from the outer periphery of the rubber grindstone 30 (the insertion opening of the glass substrate 10) to the inside as shown in FIG. Insertion of the glass substrate 10 can be guided. As shown in FIG. 5, the first processed surface 31 and the second processed surface 32 may be in contact with each other at the back of the gap 33.

  Guide tapers 31 a and 32 a that guide the insertion of the glass substrate 10 may be formed on the first processed surface 31 and the second processed surface 32. The interval between the guide tapers 31a and 32a is continuously narrowed from the outer periphery to the inner side of the rubber grindstone 30 before the glass substrate 10 is inserted.

  The gap 33 of the present embodiment continuously narrows from the outer periphery to the inner side of the rubber grindstone 30 as shown in FIG. 5 before the glass substrate 10 is inserted, but may be narrowed step by step.

  The interval S between the insertion openings of the gap 33 may be smaller than the thickness T of the glass substrate 10 before the glass substrate 10 is inserted. When the glass substrate 10 is inserted, the insertion opening of the gap 33 is pushed wide, so that the elastic restoring force of the rubber grindstone 30 is strong, the first processing surface 31 is in close contact with the first chamfered portion 11, and the second processing surface 32 is Close contact with the second chamfer 12.

  Note that the gap 33 of the present embodiment narrows from the outer periphery of the rubber grindstone 30 (the insertion opening of the glass substrate 10) toward the inside before the glass substrate 10 is inserted, but may be constant. Before the glass substrate 10 is inserted, the first processed surface 31 and the second processed surface 32 may be in contact with each other.

  The rubber of the rubber grindstone 30 may be either natural rubber or synthetic rubber. Natural rubber is rubber which has polyisoprene as a main ingredient, for example. Examples of the synthetic rubber include butadiene rubber, chloroprene rubber, propylene rubber, and polyisobutylene rubber. Unlike the resin bond grindstone in which the binder is a thermosetting resin, the rubber grindstone 30 in which the binder is rubber can be elastically deformed. Therefore, it is possible to insert the glass substrate 10 between the first processed surface 31 and the second processed surface 32 and to widen the gap 33.

  The SHORE-D hardness (Japanese Industrial Standard JIS K6253) of the rubber grindstone 30 is, for example, 20 to 90. The SHORE-D hardness is not the hardness of rubber alone, but the hardness of a product obtained by bonding abrasive grains with rubber. When the SHORE-D hardness is 90 or less, the rubber grindstone 30 is easily elastically deformed when the glass substrate 10 is inserted between the first processed surface 31 and the second processed surface 32 and the gap 33 is expanded, Damage to the rubber grindstone 30 can be suppressed. Further, when the SHORE-D hardness is 20 or more, the strength of the grindstone itself is good, and the thickness of the work-affected layer can be efficiently reduced. The SHORE-D hardness is preferably 20 to 85, particularly preferably 20 to 80.

  As abrasive grains of the rubber grindstone 30, diamond abrasive grains, cubic boron nitride (CBN) abrasive grains, alumina abrasive grains, silicon carbide abrasive grains, and the like are used.

  The average particle diameter of the abrasive grains of the rubber grindstone 30 is, for example, 18 to 125 μm. When the average particle diameter of the abrasive grains of the rubber grindstone 30 is 18 μm or more, the thickness of the work-affected layer can be efficiently reduced. When the average particle diameter of the abrasive grains of the rubber grindstone 30 is 125 μm or less, the formation of new scratches and cracks due to the abrasive grains of the rubber grindstone 30 can be suppressed. The average particle diameter of the abrasive grains is the number average diameter and can be measured by an electric resistance method (Coulter method).

  The ratio of abrasive grains in the rubber grindstone 30 (ratio of abrasive grains when the total amount of abrasive grains and rubber is 100% by volume, hereinafter referred to as “abrasive grain content”) is, for example, 12 to 50% by volume. is there. When the content of abrasive grains is 50% by volume or less, the abrasive grains can be sufficiently bonded with rubber. When the content of abrasive grains is 12% by volume or more, the thickness of the work-affected layer can be efficiently reduced.

  FIG. 8 is a cross-sectional view showing a grindstone unit including a chamfering grindstone and a rubber grindstone according to an embodiment of the present invention.

  The grindstone unit includes a chamfering grindstone 20 and a rubber grindstone 30. The center line of the chamfering grindstone 20 and the center line of the rubber grindstone 30 may be arranged on the same straight line. The chamfering grindstone 20 and the rubber grindstone 30 are simultaneously rotated around their respective center lines. A chamfering step and a chamfered portion machining step can be performed using a machine that rotates the grindstone unit about its center line.

  The chamfering grindstone 20 may have a primary chamfering grindstone portion 23 and a secondary chamfering grindstone portion 24. A plurality of annular grinding grooves are formed on the outer periphery of the primary chamfering grindstone portion 23, and similarly, a plurality of annular grinding grooves are formed on the outer periphery of the secondary chamfering grindstone portion 24.

  The glass substrate 10 is inserted into the grinding groove of the primary chamfering grindstone portion 23 and ground on the wall surface of the grinding groove, and then inserted into the grinding groove of the secondary chamfering grindstone portion 24 and ground on the wall surface of the grinding groove. The The average particle size of the abrasive grains of the secondary chamfering grindstone portion 24 may be smaller than the average particle size of the abrasive grains of the primary chamfering grindstone portion 23.

  The chamfering grindstone 20 may further include a tertiary chamfering grindstone portion, and the number of chamfering grindstone portions is not limited.

  The chamfering grindstone 20 and the rubber grindstone 30 may be detachable. For example, a male screw 39 is formed on the rubber grindstone 30, and a female screw 29 is formed on the chamfering grindstone 20. The The arrangement of the male screw and the female screw may be reversed, the female screw may be formed on the rubber grindstone 30, and the male screw may be formed on the chamfering grindstone 20.

  [Examples 1 to 6] In Examples 1 to 6, a disk-shaped glass substrate having a circular hole at the center is prepared, and the chamfering step, the chamfered portion processing step, and the end surface polishing step are performed in this order. Repeated 100 times, 100 crow substrates for magnetic recording media were produced. In Examples 1 to 6, conditions other than those shown in Table 1 were the same.

  In the chamfering step, the electrodeposited diamond grindstone of count # 325 and the electrodeposited diamond grindstone of count # 600 are used in this order in order to form the first chamfered portion, the second chamfered portion, and the side surface on the inner peripheral end surface of the glass substrate. Part was formed. Glass with a plate thickness of 0.9 mm, an inner diameter of 20 mm, an outer diameter of 65 mm, a chamfer length L (see FIG. 4) of 0.18 mm, and a chamfer angle θ (see FIG. 4) of 45 ° by the chamfering process. A substrate was obtained. The shape and dimensions of the glass substrate after the chamfering process were stable from the first sheet to the 100th sheet in each example.

  In the chamfered portion machining step, as shown in Table 1, rubber grindstones were used in Examples 1 to 4, resin bond grindstones were used in Example 5, and vitrified bond grindstones were used in Example 6. In Examples 1 to 4, as shown in FIG. 6, a glass substrate is inserted between the first processing surface and the second processing surface of the rubber grindstone to push the gap between the first processing surface and the second processing surface. The first chamfered portion was processed on the first processed surface and the second chamfered portion was processed on the second processed surface. In Example 5, the glass substrate was pressed against the wall surface of the grinding groove formed on the outer periphery of the resin bond grindstone to process the first chamfered portion, the second chamfered portion, and the side surface portion. In Example 6, the glass substrate was pressed against the wall surface of the grinding groove formed on the outer periphery of the vitrified bond grindstone to process the first chamfered portion, the second chamfered portion, and the side surface portion. In each example, the distance between the center of rotation of the glass substrate and the center of rotation of the glass substrate was constant from the 1st sheet to the 100th sheet, such as a rubber grindstone (including a resin bond grindstone and a vitrified bond grindstone).

  The SHORE-D hardness of the rubber grindstone was measured with a rubber hardness meter (manufactured by Bareiss, Digitest II BS06). Measurement conditions were based on JIS K6253. The resin bond grindstone and the vitrified bond grindstone were too hard to measure the hardness.

  The average particle diameter of abrasive grains such as a rubber grindstone was measured using a particle size distribution measuring device (manufactured by Beckman Coulter, Multisizer 3).

  After the chamfered part processing step and before the end surface polishing step, the inner diameter of the glass substrate is measured by an inner diameter measuring machine (manufactured by Keyence, VM8040), and the inner diameter difference between the first sheet and the 100th sheet is obtained as the inner diameter change. It was. In the evaluation of the inner diameter change, “A” is the case where the inner diameter difference between the first sheet and the 100th sheet is 4 μm or less, “B” when the difference is larger than 4 μm and smaller than 8 μm, and “C” when the difference is 8 μm or more. .

  Further, the surface roughness of the first chamfered portion was measured with a laser microscope (OLYmpus, LEXT OLS4000) after the chamfered portion processing step and before the end face polishing step. The magnification of the objective lens was 20 times, and the cutoff value was 0.08 mm. The surface roughness of the first chamfered portion and the surface roughness of the second chamfered portion were substantially the same.

  In the end surface polishing step, the inner peripheral end surface of the glass substrate after the chamfered portion processing was polished with a rotating brush. A polishing liquid containing cerium oxide was supplied to a polishing portion with a rotating brush. The polishing amount was 13 μm. After the end face polishing step, the presence or absence of a work-affected layer was evaluated.

  The presence or absence of the work-affected layer was examined by immersing the glass substrate after the end face polishing step in an acidic solution containing hydrofluoric acid and etching it by 5 μm. When the work-affected layer remains, etching progresses isotropically centering on scratches and the like, and dimples are formed. The presence or absence of the work-affected layer was examined by examining the presence or absence of the dimple with a laser microscope. In the evaluation of the presence or absence of the work-affected layer, the case where the work-affected layer remains was “A”, and the case where it did not remain was “B”.

  The test results are shown in Table 1 together with the test conditions.

表１から明らかなように、例１〜４では、面取部加工工程においてゴム砥石を用いたため、１枚目と１００枚目とでガラス基板の内径差が小さく、面取部の表面粗さＲａが０．３μｍ以下であり、端面研磨工程後に加工変質層が残らなかった。一方、例５では、面取部加工工程においてレジンボンド砥石を用いたため、砥石の摩耗によるガラス基板の形状変化が大きく、１枚目と１００枚目とでガラス基板の内径差が大きかった。また、例６では、面取部加工工程においてビトリファイドボンド砥石を用いたため、砥石の摩耗によるガラス基板の形状変化が大きく、１枚目と１００枚目とでガラス基板の内径差が大きかった。さらに例６では、ビトリファイドボンド砥石を用いたため、面取部の表面粗さが大きかった。

As is clear from Table 1, in Examples 1 to 4, since the rubber grindstone was used in the chamfered portion processing step, the difference in the inner diameter of the glass substrate was small between the first and the 100th and the surface roughness of the chamfered portion. Ra was 0.3 μm or less, and no work-affected layer remained after the end face polishing step. On the other hand, in Example 5, since a resin bond grindstone was used in the chamfered portion machining step, the shape change of the glass substrate due to wear of the grindstone was large, and the inner diameter difference between the first and the 100th glass substrate was large. In Example 6, since a vitrified bond grindstone was used in the chamfered portion machining step, the shape change of the glass substrate due to wear of the grindstone was large, and the inner diameter difference between the first and the 100th glass substrate was large. Furthermore, in Example 6, since the vitrified bond grindstone was used, the surface roughness of the chamfered portion was large.

  As mentioned above, although embodiment of the manufacturing method of the glass substrate for magnetic recording media as a plate-shaped object was described, this invention is not limited to the said embodiment etc., The summary of this invention described in the claim Various modifications and improvements are possible within the range.

  For example, the method of manufacturing a glass substrate for a magnetic recording medium as a plate has a base plate processing step (step S11) and a main surface polishing step (step S15) as shown in FIG. 1, depending on the type of plate. May not have a base plate processing step and a main surface polishing step.

DESCRIPTION OF SYMBOLS 10 Glass substrate 11 1st chamfering part 12 2nd chamfering part 13 Side surface part 15 1st main surface 16 2nd main surface 20 Chamfering grindstone 21 Grinding groove 30 Rubber grindstone 31 1st process surface 32 2nd process surface 33 Crevice 40 Rotating brush 41 Rotating shaft 42 Brush hair

Claims (8)

A chamfering step of forming a chamfered portion and a side portion on the end face of the plate-like body and a first major surface and a second major surface and the end face, the end face is polished by a rotating brush the chamfered portion and the side portions A method for producing a plate-like body, comprising a polishing step,
After the chamfering step, before the end face polishing step, it has a chamfered portion processing step of processing the chamfered portion with a rubber grindstone,
The chamfered portion has a first chamfered portion on the first main surface side and a second chamfered portion on the second main surface side,
The rubber grindstone has a plurality of abrasive grains and a rubber that binds the plurality of abrasive grains, and has a first processing surface and a second processing surface that come into contact with the plate-like body,
In the chamfered portion processing step, the first processed surface and the second processed surface so that the first processed surface is in contact with the first chamfered portion and the second processed surface is in contact with the second chamfered portion. the plate-like body is inserted, said second working surface and said first work surface and the second processing surface and the side surface portion and the first processing surface before SL such that a space is formed which is surrounded by between And manufacturing the plate-like body by expanding the gap formed between the first processed surface and processing the first chamfered portion on the first processed surface and processing the second chamfered portion on the second processed surface. .   The said clearance gap is a manufacturing method of the plate-shaped object of Claim 1 which becomes narrow toward the inner side from the outer periphery of the said rubber grindstone before insertion of the said plate-shaped object.   The plate-like body manufacturing method according to claim 1 or 2, wherein an interval between the insertion openings of the gap is smaller than a thickness of the plate-like body before the plate-like body is inserted.   The manufacturing method of the plate-shaped object of any one of Claims 1-3 whose SHORE-D hardness of the said rubber grindstone is 20-90.   The manufacturing method of the plate-shaped body of any one of Claims 1-4 whose average particle diameter of the said abrasive grain of the said rubber grindstone is 18-125 micrometers.   The manufacturing method of the plate-shaped object of any one of Claims 1-5 whose ratio of the said abrasive grain which occupies for the said rubber grindstone is 12-50 volume%.   The said plate-shaped body is a manufacturing method of the plate-shaped body of any one of Claims 1-6 which is a glass plate. The manufacturing method of the plate-shaped object of any one of Claims 1-7 which implements chemical strengthening to the said plate-shaped object after the said end surface grinding | polishing process.

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