JP5327275B2 - End polishing brush and method for manufacturing glass substrate for magnetic recording medium - Google Patents

Description

  The present invention relates to an end face polishing brush and a method for producing a glass substrate for a magnetic recording medium using the end face polishing brush.

  In recent years, with high density recording of magnetic disks, required characteristics for glass substrates for magnetic recording media have become stricter. In particular, when polishing the end face of a disk-shaped glass substrate for a magnetic recording medium having a circular hole in the center, the required accuracy for the end face shape and dimensional quality of the glass substrate is high.

  In the manufacturing process of the glass substrate for magnetic recording medium, end face polishing is performed in order to remove the scratches and irregularities on the side surface portion and chamfered portion of the glass substrate and finish it to a smooth mirror surface. By finishing the side surface and chamfered portion of the glass substrate into a smooth mirror surface, the mechanical strength of the glass substrate is improved. In addition, the number of foreign substances trapped by the unevenness of the side surface portion and the end surface portion is reduced, and particles generated by the unevenness of the side surface portion and the end surface portion scraping the resin member of the cassette are reduced.

  In the inner peripheral end surface polishing of the glass substrate, for example, a glass substrate laminate in which glass substrates are laminated is mounted on an end surface polishing apparatus, and polishing is performed by inserting a polishing brush into the glass substrate laminate. However, when the polishing brush is pushed into the inner peripheral end face of the glass substrate laminate, the shaft of the polishing brush is bent due to the repulsion of the glass substrate laminate.

  Therefore, Patent Document 1 discloses a technique for suppressing the bending of the polishing brush by polishing the glass substrate laminate in a state where a downward load is applied to the polishing brush.

JP 2006-007350 A

  However, the method of Patent Document 1 requires a mechanism for applying a downward load, and has a problem that the end surface polishing apparatus has a complicated configuration. Moreover, the grinding | polishing dispersion | variation in a glass substrate laminated body and the grade of a mirror surface defect were not actually evaluated.

  Accordingly, an object of the present invention is to provide an end surface polishing brush that uniformly and stably polishes an inner peripheral chamfered portion and an inner peripheral side surface portion without using an end surface polishing apparatus having a complicated configuration.

According to the present invention,
An end face polishing brush for polishing an inner peripheral end face of a glass substrate for a magnetic recording medium having a circular hole in the center,
The end surface polishing brush is provided with an end surface polishing brush in which brush hair is planted on a shaft, and the shaft has a maximum deflection amount of 390 μm or less when a load of 19.6 N is applied.

  The present invention has the following effects.

  An end surface polishing brush for uniformly and stably polishing the inner peripheral chamfered portion and the inner peripheral side surface portion can be provided without using an end surface polishing apparatus having a complicated configuration.

FIG. 1 is a perspective cross-sectional view for explaining a configuration of a glass substrate according to the method for manufacturing a glass substrate of the present invention. FIG. 2 is a schematic view showing a state of polishing of the inner peripheral end face of the glass substrate. FIG. 3 is a schematic cross-sectional view of the end surface polishing brush of the present invention. FIG. 4 is an enlarged cross-sectional view of the end surface polishing brush of the present invention.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

  First, the structure of a glass substrate for a magnetic recording medium that is polished with the end face polishing brush of the present invention will be described. In FIG. 1, the example of a perspective sectional view for demonstrating the structure of a glass substrate is shown. In FIG. 1, a glass substrate 1 has a donut shape having a circular hole 3 at the center of a main surface 2. The side surface on the outer peripheral side of the glass substrate 1 is an outer peripheral end surface 4, and the side surface of the circular hole 3 is an inner peripheral end surface 7. The outer peripheral end surface 4 includes an outer peripheral side surface portion 5 having an angle of 90 degrees with respect to the main surface 2 and an outer peripheral chamfered portion 6 in contact with the main surface 2 and the outer peripheral side surface portion 5. The inner peripheral end surface 7 includes an inner peripheral side surface portion 8 having an angle of 90 degrees with respect to the main surface 2, and an inner peripheral chamfered portion 9 in contact with the main surface 2 and the inner peripheral side surface portion 8.

  FIG. 2 is a schematic view showing a state of polishing of the inner peripheral end face of the glass substrate for a magnetic recording medium. When polishing the inner peripheral end face of the magnetic recording medium glass substrate, a plurality of disk-shaped glass substrates are usually overlapped with the positions of the circular holes to form a glass substrate laminate. At this time, as shown in FIG. 2, for example, a spacer 10 may be inserted between the adjacent disk-shaped glass substrates 1. Inserting the spacer 10 makes it easier for brush bristles and polishing liquid to reach the boundary between the main surface 2 and the inner peripheral chamfered portion 9, so that the inner peripheral end surface 7 can be more uniformly polished. Moreover, the damage to the main surface of a glass substrate can be prevented. Usually, in the glass substrate laminate, the center of the circular hole of the spacer 10 and the circular hole of the glass substrate has the same central axis, and this central axis extends in a direction perpendicular to the main surface 2 of the glass substrate 1.

  The inner diameter of the circular hole of the spacer 10 is preferably slightly larger than the diameter formed by the boundary portion between the main surface 2 of the glass substrate 1 and the inner peripheral chamfered portion 9. By making the inner diameter of the spacer 10 slightly larger than the diameter formed by the boundary between the main surface 2 of the glass substrate 1 and the inner peripheral chamfered portion 9, the entire surface of the inner peripheral chamfered portion 9 can be uniformly polished. Furthermore, the thickness of the spacer 10 is preferably 0.2 mm to 0.5 mm. If the thickness of the spacer 10 is less than 0.2 mm, it may be difficult to uniformly polish the entire surface of the inner peripheral chamfered portion 9. On the other hand, when the thickness of the spacer 10 exceeds 0.5 mm, the size of the glass substrate laminate is increased, which is not preferable. In addition, it does not specifically limit as a material of the spacer 10, For example, rubber | gum, a plastic, an aluminum alloy, stainless steel etc. can be used.

  A plurality of laminated glass substrate laminates 11 are installed in a holding unit that holds a glass substrate laminate of a known inner peripheral end surface polishing apparatus. Thereafter, an end face polishing brush 12 to be described later is inserted into the circular hole 3 formed in the central portion of the glass substrate laminate 11, and the brush bristles 13 are attached to the inner peripheral side surface portion 8 and the inner peripheral chamfered portion 9 of the glass substrate. Make contact. Next, a polishing liquid containing abrasive grains is supplied to the inner peripheral side surface portion 8 and the inner peripheral chamfered portion 9 of the glass substrate. In this state, the glass substrate laminate 11 and the end surface polishing brush 12 are rotated in opposite directions to advance polishing.

  At this time, for example, the end surface polishing brush 12 may be pressed against the glass substrate laminate 11 by about 1.5 to 2.0 mm. Further, the end surface polishing brush 12 may be polished by reciprocating in the brush insertion direction. The reciprocating distance when the end surface polishing brush 12 is reciprocated is preferably 15% or more with respect to the length in the laminating direction of the glass substrate laminate. When the reciprocating distance of the end surface polishing brush 12 is less than 15% with respect to the length in the stacking direction of the glass substrate laminate, the variation in the characteristics in the axial direction of the polishing brush causes a variation in the glass substrate stack. Variation in the polishing amount may occur.

  In FIG. 2, six disk-shaped glass substrates are stacked to form a glass substrate laminate, but the present invention is not limited to this. There is no restriction | limiting in particular as the number of the some disk-shaped glass substrates to overlap | superpose, For example, a glass substrate laminated body can be formed by superimposing 100, 200, and 300 glass substrates. In general, by increasing the number of glass substrates to be stacked, many glass substrates can be polished simultaneously, which is preferable from the viewpoint of economy and efficiency.

[End polishing brush]
FIG. 3 is a schematic cross-sectional view of the end surface polishing brush 12 according to the present invention. FIG. 4 shows an enlarged sectional view thereof. The end surface polishing brush 12 mainly includes a cylindrical shaft 14 and brush hairs 13 installed on the shaft 14. The bristles 13 are planted in a direction substantially perpendicular to the axial direction of the shaft 14.

The maximum deflection amount δ (μm) at the center of the cylindrical shaft 14 in the axial direction is usually the applied load P (N), the axial length L (mm) of the shaft 14, the shaft diameter r (the radius of the bottom surface). ) (Mm), which is defined by the following formula (1) using the Young's modulus E (GPa) of the constituent material.
δ = PL ³ / (12πr ⁴ E) (1)
An example is given below as a method for measuring the maximum deflection amount of the formula (1), but the present invention is not limited in this respect. Support the inner side 10mm from both ends of the shaft in the axial direction, apply a 19.6N load to the central portion of the shaft in the axial direction with a push-pull gauge, etc. The method of measuring by etc. is mentioned.

  In the end surface polishing brush 12 of the present invention, the amount of deflection when a load of 19.6 N is applied to the shaft 14 is preferably 420 μm or less, more preferably 400 μm or less, and further preferably 300 μm or less. The thickness is preferably 250 μm or less. By using an end surface polishing brush having a deflection of 420 μm or less when a load of 19.6 N is applied to the shaft 14, the glass substrate laminate can be uniformly polished without the shaft being bent during the inner peripheral end surface polishing. . Specifically, polishing variation within the same glass substrate laminate lot can be reduced to 7 μm or less, and uniform and stable polishing of the inner peripheral chamfered portion and the inner peripheral side surface portion is achieved. At this time, the Young's modulus E of the shaft, the radius r of the bottom surface of the shaft, and the length L of the shaft are not particularly limited as long as the deflection amount δ of the shaft satisfies the above-described condition based on the formula (1). .

  The method of planting the bristle 13 on the end surface polishing brush 12 is not particularly limited, and for example, as shown in FIG. 3, there is a method of winding and fixing the channel component 15 in which the bristle 13 is implanted around the shaft 14. In addition, a method in which the bristles 13 are directly planted in a concave groove formed in the shaft 14 may be employed. The method of winding and fixing the channel component 15 in which the bristles 13 are planted around the shaft 14 is preferable because the degree of freedom in designing the end surface polishing brush 12 is high.

  Further, the length 16 (hereinafter referred to as the flocked length 16 (see FIG. 3)) of the flocked portion 18 where the bristles are planted in the shaft 14 may be set longer than the total length of the glass substrate laminate 11. The inner peripheral end face polishing can be progressed uniformly, and a sufficient polishing rate can be secured, which is preferable.

  Furthermore, the ratio of the length 16A of the flocked portion 18A to the total (flocked length 16) of the length 16A of the flocked portion 18A and the length 16B of the non-flocked portion 18B in the flocked portion 18 (the area ratio of the flocked portion) Is preferably 25 to 95%, more preferably 30 to 90%, and still more preferably 30 to 85%. When the area ratio of the flocked portion is lower than 25%, the polishing rate may be slow. On the other hand, when the area ratio of the flocked portion is higher than 95%, when the end surface polishing brush is pressed against the glass substrate laminate, the repulsion due to the glass laminate increases, so the shaft 14 of the end surface polishing brush 12 is bent, The inner peripheral chamfered portion may not be sufficiently polished.

  In addition, as a measuring method of the area ratio of the flocked part, for example, a method in which the length occupied by the flocked part 18A in the unit length (for example, 100 mm) in the axial direction of the shaft is measured and obtained by calculation from the measured value, etc. Is mentioned. In addition, when using the channel component 15, the width | variety of the flocked location which occupies for the channel component 15, the pitch width 19 of the channel component 15, etc. will not be restrict | limited especially if the area ratio of a flocked location will be 25-95%.

  The outer diameter 20 of the end surface polishing brush 12 including the shaft, the brush bristles, and the channel parts may be larger or smaller than the diameter of the circular hole of the glass substrate on which the inner peripheral end surface is polished. When the outer diameter 20 of the end surface polishing brush 12 is smaller than the diameter of the circular hole of the glass substrate, it is necessary to move the end surface polishing brush 12 until it contacts the inner peripheral end surface of the glass substrate.

  When the length 21 of the bristle is too long, the bristle cannot be brought into contact with the inner peripheral end surface of the glass substrate with an appropriate pressure, and the polishing rate may be reduced. On the other hand, if the length of the brush bristles is too short, it may be difficult to ensure that the bristles reach the back of the inner chamfered portion of the glass substrate, so the polishing of the inner chamfered portion may not proceed sufficiently. is there. Therefore, an appropriate brush hair is selected according to the diameter of the shaft, the outer diameter 20 of the end surface polishing brush 12, the diameter of the circular hole of the glass substrate, the height 17 of the channel component, and the material and wire diameter of the brush hair described later. It is important to select the length.

  Brush hair materials include nylon fibers, polypropylene fibers, vinyl chloride fibers, polybutylene terephthalate fibers, and other synthetic synthetic fibers, animal hair such as pigs and horses, metal wires such as piano wires and stainless fibers, and carbon fibers. Those skilled in the art can appropriately select from conventional brush hairs.

  The wire diameter of the brush bristles is preferably 0.1 mm to 0.3 mm, although it depends on the length of the bristles described above. When the wire diameter of the bristle is less than 0.1 mm, the bristle cannot be brought into contact with the inner peripheral end surface of the glass substrate with an appropriate pressure, and the polishing rate may decrease. Further, the change with time of the brush hair may become large. On the other hand, when the wire diameter of the brush bristle exceeds 0.3 mm, it becomes difficult to reliably reach the brush bristle to the back of the inner peripheral chamfered portion of the glass substrate, so that the inner peripheral chamfered portion is sufficiently polished. May not.

[Polishing liquid]
The polishing liquid for polishing using the end face polishing brush of the present invention is not particularly limited. As an example, the following abrasive grains are obtained by dispersing in water or a water-soluble organic solvent. A dispersing agent, a pH adjuster, a viscosity adjuster, a chelating agent, and the like can be added to the polishing liquid as necessary.

  The abrasive grains contained in the polishing liquid are not particularly limited. For example, rare earth oxides such as cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide, silicon carbide, manganese oxide, iron oxide, diamond, boron nitride A polishing liquid containing abrasive grains such as zircon can be used. Among the abrasive grains described above, it is preferable to use abrasive grains containing cerium oxide, zirconium oxide, aluminum oxide, and zircon. One type of these abrasive grains may be used alone, or two or more types may be used in combination.

  It does not specifically limit as an average particle diameter (D50) of an abrasive grain, Usually, they are 0.5 micrometer-5 micrometers, Preferably they are 0.5 micrometer-2 micrometers, More preferably, they are 0.7 micrometer-1.5 micrometers.

[Method for producing glass substrate for magnetic recording medium]
Hereinafter, the manufacturing method of the glass substrate for magnetic recording media of this invention is demonstrated.

  In the method for producing a glass substrate for a magnetic recording medium of the present invention, other steps are not particularly limited as long as the inner peripheral end surface is polished using the end surface polishing brush of the present invention.

As an example, generally, a glass substrate for a magnetic recording medium is
(1) A shape imparting step of chamfering the inner peripheral side surface and the outer peripheral side surface after processing the glass base substrate into a disk shape having a circular hole in the central portion;
(2) An outer peripheral end surface polishing step for polishing the outer peripheral end surface of the glass substrate,
(3) The inner peripheral end face of the glass substrate is polished. Inner peripheral edge polishing process,
(4) a main surface polishing step for polishing the upper and lower main surfaces of the glass substrate;
(5) A cleaning step of precisely cleaning and drying the glass substrate to obtain a glass substrate for a magnetic recording medium,
It is manufactured by such processes. Although this invention is not limited to the said method, in the inner peripheral end surface grinding | polishing process of (3), the inner peripheral end surface of a glass substrate is grind | polished using the end surface polishing brush of this invention.

  Either the (2) outer peripheral end surface polishing step or the (3) inner peripheral end surface polishing step may be performed first. In addition, at least one of the end surface polishing steps (2) and (3) before and after the end surface polishing step, a main plane lapping (for example, loose abrasive lapping, fixed abrasive lapping, etc.) may be performed. Glass substrate cleaning (inter-process cleaning) and glass substrate surface etching (inter-process etching) may be performed. Note that the main plane lapping here is polishing of the main plane in a broad sense.

  The polishing step may be only primary polishing, primary polishing and secondary polishing may be performed, or tertiary polishing may be performed after secondary polishing.

  In the present invention, the glass substrate for a magnetic recording medium may be amorphous glass, crystallized glass, or tempered glass (for example, chemically tempered glass) having a tempered layer on the surface layer of the glass substrate. As an example, when high mechanical strength is required for a glass substrate for magnetic recording media, a strengthening step (for example, a chemical strengthening step) for forming a reinforcing layer on the surface layer of the glass substrate is performed. The strengthening step may be performed either before the first polishing step, after the last polishing step, or between each polishing step. The glass substrate of the glass substrate of the present invention is produced by a method such as a float method, a fusion method, a redraw method, or a press molding method, but the present invention is not limited in this respect.

  Examples of the glass substrate (2) outer peripheral end surface polishing step, (4) main surface polishing step, and (5) cleaning step are given below, but the present invention is not limited thereto.

  In the outer peripheral end surface polishing step (2), scratches on the outer peripheral side surface and the outer peripheral chamfered portion of the glass substrate are removed, and the glass substrate is processed into a mirror surface. At this time, for example, polishing can be performed using a polishing liquid containing a polishing brush and abrasive grains. The abrasive grains contained in the polishing liquid are not particularly limited. For example, rare earth oxides such as cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide, silicon carbide, manganese oxide, iron oxide, diamond, boron nitride A polishing liquid containing abrasive grains such as zircon can be used. Among the abrasive grains described above, it is preferable to use abrasive grains containing cerium oxide, zirconium oxide, aluminum oxide, and zircon. One type of these abrasive grains may be used alone, or two or more types may be used in combination.

  It does not specifically limit as an average particle diameter (D50) of an abrasive grain, Usually, they are 0.5 micrometer-5 micrometers, Preferably they are 0.5 micrometer-2 micrometers, More preferably, they are 0.7 micrometer-1.5 micrometers. After the outer peripheral end surface polishing step, the cerium oxide is washed and removed and used for the next step.

  In the main plane polishing step (4), for example, the upper and lower main planes may be polished by a double-side polishing apparatus using a polishing liquid containing a hard urethane pad and cerium oxide abrasive grains as a polishing tool. Further, for example, a double-side polishing apparatus using a polishing liquid containing a soft urethane pad and cerium oxide abrasive grains (which may be cerium oxide abrasive grains having an average particle size smaller than the cerium oxide abrasive grains) as a polishing tool. The upper and lower main planes may be polished. Further, using a polishing composition mainly composed of a soft urethane pad and colloidal silica having an average primary particle size of about 20 to 30 nm as a polishing tool, the upper and lower main surfaces are subjected to final polishing by a double-side polishing apparatus. Do.

  In the cleaning step (5), the glass substrate after finish polishing is sequentially subjected to scrub cleaning using a detergent, ultrasonic cleaning in a state immersed in a detergent solution, ultrasonic cleaning in a state immersed in pure water, and the like. Dry with steam such as isopropyl alcohol.

  A magnetic disk can be manufactured by laminating layers such as an underlayer, a magnetic layer, a protective layer, and a lubricating layer on the glass substrate for a magnetic recording medium obtained by the above method. A conventional method or the like can be appropriately used as a method for laminating each layer. The size of the magnetic disk is not particularly limited. For example, 0.85 inch type magnetic disk (inner diameter 6 mm, outer diameter 21.6 mm, plate thickness 0.381 mm), 1.0 inch type magnetic disk (inner diameter 7 mm, outer Diameter 27.4 mm, plate thickness 0.381 mm), 1.8 inch type magnetic disk (inner diameter 12 mm, outer diameter 48 mm, plate thickness 0.508 mm), 2.5 inch type magnetic disk (inner diameter 20 mm, outer diameter 65 mm, plate) Magnetic disks of various sizes such as 0.635 mm and 0.8 mm in thickness can be manufactured.

Example 1
Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby.

  The deflection of the end face polishing brush used in the inner peripheral end face polishing of the example and the comparative example was fixed 10 mm inside from both ends in the axial direction of the shaft, and a load of 19.6 N was applied to the center portion of the shaft by a push-pull gauge. A value obtained by applying and measuring a moving distance of the central portion of the shaft with a dial gauge was used.

  Moreover, the end surface polishing brush used in the Examples and Comparative Examples has a channel height of 2.5 mm, a brush bristle length of 3.7 mm, a bristle wire diameter of 0.2 mm, and a flocked area ratio of 30. % Were used.

  Further, as the polishing liquid, a polishing liquid mainly composed of cerium oxide abrasive grains having an average particle diameter of 1.4 μm and a specific gravity of 1.2 was used. The detailed polishing procedure is described below.

A disk having a circular hole in the center so as to obtain a glass substrate for magnetic recording media having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.635 mm made of a glass plate mainly composed of SiO ₂ formed by the float process. Processed into shape.

  Chamfering so that the inner peripheral side surface and the outer peripheral side surface of the disk-shaped glass substrate having a circular hole in the center portion have a chamfering width of 0.15 mm and a chamfering angle of 45 ° when the glass substrate for a magnetic recording medium as a final product is used. processed. Thereafter, the upper and lower main planes of the glass substrate were ground (wrapped) using alumina abrasive grains (average particle diameter of 7 to 7.5 μm), and then the abrasive grains were washed and removed.

  Next, the glass substrate was laminated using an alignment jig to form a glass substrate laminate. In addition, a resin spacer having a thickness of 0.2 mm was inserted between the glass substrates, and a total of 200 glass plates were stacked to form a glass substrate laminate.

  The obtained glass substrate laminate was inserted into a jig for polishing the inner peripheral end surface, and was clamped in the vertical direction of the glass substrate laminate to remove the fixed ground and alignment jig from the glass substrate laminate. This glass substrate laminate is placed in the polished object holding part of the inner peripheral end surface polishing apparatus (product name: BTK-08, manufactured by TK System Co., Ltd.), and the end surface is polished in the circular hole at the center of the glass substrate laminate. A brush was inserted. The end face polishing brush used has a Young's modulus of 206 GPa, the length of the shaft part of the end face polishing brush is 375 mm, the diameter of the shaft is 50% of the diameter of the circular hole of the glass substrate, and the amount of deflection measured by the above method is 210 μm. Met.

  The end surface polishing brush was moved in one direction from the center of the circular hole of the glass substrate laminate, and a certain amount of brush hair was pushed into the inner peripheral side surface portion and the inner peripheral chamfered portion of the glass substrate laminate. While supplying the above polishing liquid to the inner peripheral end surface portion of the glass substrate laminate, rotating the polishing brush and the glass substrate laminate in opposite directions, and further swinging the end surface polishing brush in the laminating direction of the glass substrate laminate Polished.

  In this example and comparative example, the polishing liquid was set to 7 to 8 L / min, the rotation speed of the polishing brush was set to 2500 rpm, the rotation speed of the glass substrate laminate was set to 39 rpm, and the rocking speed was set to 100 to 1500 mm / min. Polishing was performed until the polishing amount of the inner peripheral side surface portion was 25 μm (12.5 μm on one side).

  After polishing the inner peripheral end face, the glass substrate laminate was removed from the inner peripheral end face polishing jig, and the glass substrates were separated from the glass substrate laminate one by one. The separated glass substrate was subjected to the following evaluation method after washing and removing the abrasive grains.

(Example 2)
The end face polishing brush used has a Young's modulus of 199 GPa, the length of the shaft part of the end face polishing brush is 375 mm, the diameter of the shaft is 50% of the diameter of the circular hole of the glass substrate, and the amount of deflection measured by the above method is 220 μm. Except that, polishing was performed in the same process as in Example 1.

(Example 3)
The end face polishing brush used has a Young's modulus of 199 GPa, the length of the shaft part of the end face polishing brush is 230 mm, the diameter of the shaft is 40% of the diameter of the circular hole of the glass substrate, and the amount of deflection measured by the above method is 120 μm. Except that, polishing was performed in the same process as in Example 1.

Example 4
The end face polishing brush used has a Young's modulus of 199 GPa, the length of the shaft part of the end face polishing brush is 230 mm, the diameter of the shaft is 30% with respect to the diameter of the circular hole of the glass substrate, and the deflection measured by the above method is 390 μm. Except that, polishing was performed in the same process as in Example 1.

(Comparative Example 1)
The used end face polishing brush has a Young's modulus of 101 GPa, the length of the shaft part of the end face polishing brush is 375 mm, the diameter of the shaft is 50% of the diameter of the circular hole of the glass substrate, and the deflection measured by the above method is 430 μm. Except that, polishing was performed in the same process as in Example 1.

(Comparative Example 2)
The end face polishing brush used has a Young's modulus of 69 GPa, the length of the shaft part of the end face polishing brush is 375 mm, the diameter of the shaft is 50% of the diameter of the circular hole of the glass substrate, and the amount of deflection measured by the above method is 640 μm. Except that, polishing was performed in the same process as in Example 1.

[Evaluation]
(Difference in polishing amount)
The amount of polishing was measured using a high-precision two-dimensional dimension measuring machine (manufactured by Keyence Corporation, product name: VM8040) obtained by washing and drying the glass substrate before end face polishing and the glass substrate obtained after end face polishing. . Specifically, the diameter of the circular hole in the central portion of the glass substrate was measured at the inner peripheral side surface portion, and the difference in circular hole diameter before and after end face polishing was taken as the polishing amount.

  20 sheets were arbitrarily extracted from 200 glass substrate laminate lots, the above-mentioned polishing amount was measured, and the difference between the maximum value and the minimum value was defined as the difference in polishing amount in the same lot.

(Number of pit defects)
The inner peripheral end face of the polished glass substrate is etched 5 μm in the depth direction using an acidic etching solution containing hydrofluoric acid and nitric acid. As a result, the work-affected layer (scratches) can be easily observed as pit defects. Thereafter, washing and drying are performed. Finally, the glass substrate was cut so that the number of pit defects could be easily evaluated, and a pit defect number observation sample including the inner peripheral side surface portion 8 and the inner peripheral chamfered portion 9 was produced.

  The number of pit defects was counted and evaluated using an optical microscope (manufactured by Olympus, bright field / differential interference metal microscope BX60M). Each observation sample was fixed to the sample stage, and fixed so that the surface of the inner peripheral side surface portion 8 or the inner peripheral chamfered portion 9 was parallel to the lens surface of the objective lens of the optical microscope. The objective lens of the optical microscope was 20 times, the observation visual field was 480 μm × 328 μm, and the number of circular or elliptical pit defects having a diameter of 10 μm or more was counted. Then, a numerical value obtained by dividing the measured number of pit defects by the observation area was calculated.

In 200 glass substrate laminate lots, roughly classify them as upper, middle, and lower, and arbitrarily three samples are taken from each classified location and measured by the method described above, and the average of the numerical values is the number of pit defects. did. Usually, a polishing method in which the obtained numerical value is smaller than 5 pieces / mm ² is preferable, and a polishing method including 5 pieces / mm ² or more is not preferable.

本発明の端面研磨ブラシは、荷重１９．６Ｎを付与した場合のたわみ量が４２０μｍ以下であるため、ガラス基板の内周面取り部と内周側面部とを均一かつ安定的に研磨できる。

Since the end surface polishing brush of the present invention has a deflection amount of 420 μm or less when a load of 19.6 N is applied, the inner peripheral chamfered portion and the inner peripheral side surface portion of the glass substrate can be uniformly and stably polished.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Main surface 3 Circular hole 4 Outer peripheral end surface 5 Outer peripheral side surface portion 6 Outer peripheral chamfered portion 7 Inner peripheral end surface 8 Inner peripheral side surface portion 9 Inner peripheral chamfered portion 10 Spacer 11 Glass substrate laminated body 12 End surface polishing brush 13 Brush hair 14 Shaft 15 Channel part 16 Flocking length 17 Channel part height 18 Flocking part 19 Channel part pitch width 20 Outer surface polishing brush outer diameter 21 Brush hair length

Claims (8)

An end face polishing brush for polishing an inner peripheral end face of a glass substrate for a magnetic recording medium having a circular hole in the center,
The end surface polishing brush has an end surface polishing brush in which brush hair is planted on a shaft, and the shaft has a maximum deflection amount of 390 μm or less when a load of 19.6 N is applied. The end face polishing brush according to claim 1, wherein the shaft has a Young's modulus of 199 GPa or more.   In the shaft, the flocked part in which the brush hair is flocked includes a flocked part and a non-flocked part, and the total length of the shaft in the axial direction of the flocked part and the axial length of the non-flocked part. The end surface polishing brush according to claim 1 or 2, wherein a ratio of an axial length of the flocked portion to 25 to 95%. A shape imparting step of forming a disk-shaped glass substrate having a circular hole in the center part, having an inner peripheral side part, an outer peripheral side part, and a main surface;
An inner peripheral chamfering step for forming an inner peripheral chamfered portion at an intersection between the inner peripheral side surface portion and the main surface of the glass substrate;
An inner peripheral end surface polishing step for polishing the inner peripheral side surface portion and the inner peripheral chamfered portion;
A main surface polishing step for polishing the main surface of the glass substrate;
With
The inner peripheral end surface polishing step includes:
Laminating a plurality of the glass substrates, supplying a polishing liquid containing abrasive grains to the inner peripheral side surface portion and the inner peripheral chamfered portion of the laminated glass substrate;
The shaft is brushed with bristles, and the shaft has a maximum deflection of 390 μm or less when a load of 19.6 N is applied. A step of contacting the peripheral chamfered portion;
The manufacturing method of the glass substrate for magnetic recording media containing this.   The diameter of the said shaft is a manufacturing method of the glass substrate for magnetic recording media of Claim 4 which is 30%-60% of the diameter of the said circular hole. The method for producing a glass substrate for a magnetic recording medium according to claim 4, wherein the shaft has a Young's modulus of 199 GPa or more. When the inner peripheral end face of the glass substrate after the inner peripheral end face polishing in the inner peripheral end face polishing step is etched by 5 μm in the depth direction of the glass substrate with an etching solution, the diameter of the inner peripheral chamfered portion is 10 μm or more. 5 circular / elliptical pit defects / mm ² The manufacturing method of the glass substrate for magnetic recording media as described in any one of Claims 4 thru | or 6 which is less than. A glass substrate for a magnetic recording medium manufactured by the method for manufacturing a glass substrate for a magnetic recording medium according to any one of claims 4 to 7,
  When the inner peripheral end surface of the glass substrate for magnetic recording medium is etched by 5 μm in the depth direction of the glass substrate with an etching solution, a circular or elliptical pit defect having a diameter of 10 μm or more at the inner peripheral chamfered portion is 5 / mm ² The glass substrate for magnetic recording media which is less than.

Images