Glass substrate, manufacturing method of glass substrate, and manufacturing method of glass substrate for magnetic disk

Abstract

To provide a method for manufacturing a glass substrate, capable of surely separating and extracting a predetermined shaped glass substrate from a glass blank, and a method for manufacturing a magnetic disk.SOLUTION: A method for manufacturing a glass substrate having an opening comprises steps of: forming inner and outer peripheral circle parts obtained by irradiating the surface of a glass blank 20 being the origin of the glass substrate along an approximately concentric circle with a laser beam; relatively, thermally expanding an outer part 24 of the outer peripheral circle part of the glass blank to an inner part 26 of the outer peripheral circle part by heating the outside part of the outer peripheral circle part to form a gap in the outer peripheral circle part and separate the inner part of the outer peripheral circle part from the outer part of the outer peripheral circle part; and relatively, thermally expanding the outer part of the inner peripheral circle part of the glass blank by heating the outer part of the inner peripheral circle part to form a gap in the inner peripheral circle part and separate the inner part of the inner peripheral circle part from the outer part of the inner peripheral circle part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a glass substrate by processing a glass substrate into a shape using a laser beam. and a method for manufacturing a magnetic disk. [Background technology]

[0002] Today, personal computers, laptops, or DVDs ( Digital Versatile Disc (CD) recording device or cloud computing Hard disk drives are used for data recording in data centers for computing. In hard disk drives, a magnetic layer is formed on a disk-shaped non-magnetic glass substrate for the magnetic disk. The magnetic disk has a flying height of about 5 nm. It is incorporated into a DFH (Disk Flying Height) type magnetic head, which is It can be enjoyed.

[0003] In such a DFH type magnetic head, the flying distance is short, so the flying distance of the magnetic disk It is necessary to prevent the adhesion of fine particles to the main surface. Therefore, it is desirable that the surface roughness of the glass substrate be small not only on the main surface but also on the edge surface. It's nice.

[0004] In order to satisfy such requirements for the magnetic disk, the inner edge of the glass substrate for the magnetic disk is A technology for efficiently manufacturing glass substrates with reduced surface roughness is known (Patent Document 1). Specifically, the focal line of the pulsed laser beam is directed to multiple positions within the substrate, and the glass is then removed at multiple positions. Absorbing the material into the substrate to create a through-hole defect line on a predetermined first path, and Then, the glass substrate is heated along the first path to propagate the crack and remove the first The inner part is separated from the glass substrate by heating the inner part. Extract. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-083320 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above technique, the glass substrate is heated along the first path to propagate the crack. Although it is possible to separate the inner part of the glass substrate from the first pass by using the It was not possible to heat the part and remove it from the glass substrate stably. After forming the defect using a laser, the glass substrate is heated along the first pass to advance the crack. When the inner part of the glass substrate is separated from the first pass by spreading the glass substrate, cracks may occur. In some cases, the separation may re-adhere due to heat, making it impossible to separate completely. In this case, heat the inner part. It was found that the re-adhered parts could not be separated even by heating. For this reason, a glass substrate having a reduced surface roughness on the inner end surface of the glass substrate is manufactured by using a laser beam. It was difficult to produce efficiently. In addition, in recent years, the thickness of glass substrates has become thinner, so separation by laser irradiation and heating is becoming more difficult. In this respect, it is important to reliably manufacture thin glass substrates. It is hoped that this will happen.

[0007] Therefore, in the present invention, in order to reduce the surface roughness of the end face of the glass substrate, a laser beam is used. When processing the raw glass plate that is the base of the glass substrate, a glass of a predetermined shape is cut from the raw glass plate. Glass substrate manufacturing method that can reliably separate and extract glass substrates and this manufacturing method The present invention aims to provide a method for manufacturing a magnetic disk using this method. [Means for solving the problem]

[0008] One aspect of the present invention is a method for manufacturing a glass substrate having an opening, the method comprising the steps of: The surface of the raw glass plate from which the glass substrate was made was irradiated with laser light along approximately concentric circles. forming an inner circular portion and an outer circular portion; By heating the outer portion of the outer circumferential circle, the outer portion of the outer circumferential circle of the glass plate is The outer circumferential portion is thermally expanded relative to the inner portion to form a gap in the outer circumferential portion. and separating the inner portion of the outer circumferential portion from the outer portion of the outer circumferential portion. , By heating the outer portion of the inner circumferential circle, the outer portion of the inner circumferential circle of the raw glass plate The inner circumferential portion is thermally expanded relative to the inner circumferential portion to form a gap at the inner circumferential portion. separating the outer portion of the inner circumferential portion from the outer portion of the inner circumferential portion; Equipped with.

[0009] Another aspect of the present invention is a method for manufacturing a glass substrate, the method comprising the steps of: A laser beam is applied to the surface of the raw glass plate that is the base of the glass substrate along a line that forms a predetermined ring shape. irradiating to form a defect on the line; In the outer and inner parts of the glass plate having the defect formed therein, By increasing the heating of the outer portion compared to the inner portion, separating an outer portion and the inner portion; Equipped with.

[0010] the glass substrate has a ring shape with an opening; In the step of forming the defect, the shape of the outer edge of the ring shape is changed by the laser light. forming the defect in the predetermined shape; In the step of separating the outer portion from the inner portion, In addition, the heating of the first outer portion of the glass plate is performed by dividing the first outer portion of the glass plate by the outer edge of the ring shape. It is preferable to carry out a first heat treatment to make the temperature higher than that of the first inner portion of the lath blank.

[0011] In the step of separating the outer portion from the inner portion, the annular shape of the glass substrate is As a margin, a length of 0.1% to 5% of the outer diameter of the annular shape is left, and the first outer Preferably, the side portion and said first inner portion are separate.

[0012] In the step of forming the defect, the annular shape having the opening is formed by the laser light. the defect is formed with the inner edge of the predetermined shape; In the step of separating the outer portion from the inner portion, The second outer portion of the glass plate is heated by the inner edge of the ring-shaped glass plate. and then performing a second heat treatment to make the temperature of the second inner portion of the raw material glass plate higher than that of the second inner portion of the raw material glass plate. I wish.

[0013] In the step of separating the portion that will become the glass substrate from the raw glass plate, After the treatment, the second heat treatment is preferably carried out.

[0014] Yet another aspect of the present invention is a method for manufacturing a glass substrate, the method comprising the steps of: A laser beam is applied to the surface of the raw glass plate that is the base of the glass substrate along a line that forms a predetermined ring shape. irradiating to form a defect on the line; In the outer and inner parts of the glass plate having the defect formed therein, By increasing the heating of the outer portion compared to the inner portion, Separating the outer portion from the inner portion, the outer portion being separated from the raw glass plate. Heating is performed simultaneously from both sides of the main surface to increase the heating of the outer portion relative to the inner portion. By this, the outer portion and the inner portion of the glass plate are separated, and the inner portion is and removing the portion that will become the opening.

[0015] In the step of separating the outer portion from the inner portion, the temperature of the outer portion is adjusted to the temperature of the inner portion. the temperature is increased relative to the temperature of the outer portion, causing the outer portion to thermally expand relative to the inner portion. forming a gap along the line to separate the outer portion from the inner portion; It is preferable that:

[0016] The laser beam is irradiated onto the surface of the raw glass plate by: After forming point-like through holes at a plurality of discrete points on the line by pulsed laser light, The laser beam is projected continuously along the line so as to connect the discrete points on the line. Preferably, the method includes automatically moving the object. The non-pulsed laser light is preferably, for example, a non-pulsed CO2 laser.

[0017] The heating is performed by radiating heat from heating sources provided on both sides of the main surface of the glass plate. Preferably, the method includes heating both main surfaces of the glass plate.

[0018] The area ratio of the main surface of the glass plate to the main surface of the glass substrate is 1. 01% to 160%, In the step of separating the outer portion and the inner portion, the glass is separated from one raw glass plate. It is preferable to remove one lath board.

[0019] The thickness of the glass plate is preferably 0.6 mm or less.

[0020] Yet another aspect of the present invention is a glass substrate manufactured by the glass substrate manufacturing method. The method further comprises forming at least a magnetic layer on the magnetic disk to fabricate the magnetic disk. This is a method for manufacturing a disk. [Effects of the Invention]

[0021] According to the above-mentioned manufacturing method of a glass substrate and a manufacturing method of a magnetic disk, a desired glass substrate is formed from a raw glass plate. Glass substrates of a specific shape can be reliably separated and extracted. [Brief explanation of the drawings]

[0022] [Figure 1] 3A to 3C are diagrams illustrating heating of an outer portion in a method for manufacturing a glass substrate according to an embodiment. [Figure 2] 10A to 10C are diagrams illustrating heating of an outer portion in a glass substrate manufacturing method according to another embodiment. [Figure 3] 3(a) is a perspective view of an example of a magnetic-disk glass substrate produced in one embodiment, and FIG. 3(b) is a diagram showing an example of a cross section of the outer end face of the magnetic-disk glass substrate shown in FIG. 3(a). [Figure 4] 3A to 3C are diagrams illustrating laser light irradiation in a glass substrate manufacturing method according to an embodiment. [Figure 5] 3A to 3C are diagrams specifically illustrating heating of a raw glass plate in a method for manufacturing a glass substrate according to an embodiment. [Figure 6]3A to 3C are diagrams illustrating laser light irradiation in a glass substrate manufacturing method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] The manufacturing method of the glass substrate and the manufacturing method of the magnetic disk will be described in detail below. The glass substrate materials are aluminosilicate glass, soda lime glass, and borosilicate glass. In particular, chemical strengthening can be performed as needed. The present invention provides a glass substrate for a magnetic disk that is excellent in the flatness of the main surface and the strength of the substrate. In this respect, amorphous aluminosilicate glass is preferably used. can.

[0024] (Outline of the manufacturing method of the glass substrate) A method for manufacturing a glass substrate according to one embodiment includes the steps of: (A) A laser beam is projected along a line forming a predetermined ring shape onto the surface of the raw glass plate that will become the glass substrate. irradiating to form defects on the lines; (B) Of the outer and inner parts of the glass plate with the defect, the outer part is the outer part. By increasing the heating of the outer and inner parts of the glass plate, and a separating step. Forming a defect means drilling a hole in the glass plate, or forming a hole and a defect that develops from this hole. The defect may be formed in the entire area of the line, i.e., the defect may be formed in the entire area of the line. In addition to forming a linear defect, it is also possible to form defects discretely at separate locations on the line. . That is, in the method for manufacturing a glass substrate according to one embodiment, a defect is formed along a line. By increasing the heating of the outer portion relative to the wire compared to the inner portion, The outer and inner portions of the lath blank are separated. The holes formed by the irradiation of the laser beam are formed by abrading the glass plate (gas It is preferable that the holes are holes that penetrate the lath blank (in the thickness direction), that is, through holes. By forming the glass plate, when the outer part is heated, the outer part and the inner part can be easily separated. The through-holes are approximately perpendicular to the main surface of the glass plate (the angle is 85°). Therefore, the separation plane of the outer and inner parts is , a wall surface that is approximately perpendicular to the main surface of the glass plate, and can be made using a conventional scriber. This is different from a wall surface that is inclined relative to the main surface, such as a fractured surface.

[0025] FIG. 1 is a diagram illustrating heating of an outer portion in a method for manufacturing a glass substrate according to an embodiment. The raw glass plate 20 is a glass plate having a substantially circular or elliptical shape. The surface of the raw glass plate 20 is irradiated with laser light along a ring-shaped line 22. Furthermore, the part that will become the glass substrate is removed from the glass plate 20 in which the defect has been formed. In order to remove the glass plate 20, the outer portion 24 is heated. By making the outer portion 24 higher than the side portion 26, the amount of thermal expansion of the outer portion 24 is made smaller than the amount of thermal expansion of the inner portion 26. As a result, the outer portion 24 thermally expands outward as shown in FIG. Therefore, a gap is reliably formed at the interface between the outer portion 24 and the inner portion 26. Therefore, the outer portion 24 and the inner portion 26 can be reliably separated. Specifically, the degree of heating of the outer portion 24 is higher than that of the inner portion 26. The inner diameter of the inner portion 24 is relatively larger than the outer diameter of the inner portion 26. The gap is formed by thermal expansion so that the outside The side portion 24 and the inner portion 26 can be separated reliably. The heating level of the inner portion 26 is higher than that of the outer portion 24. In addition to heating the portion 26, the outer portion 24 is selectively heated, but the inner portion 26 is not. This includes cases where the outer portion 24 is not heated intentionally. The inner part is indirectly heated by heat conduction through the gap or through the glass plate 20. In this case, the heating of the outer portion 24 is higher than the heating of the inner portion 26. In this specification, the "gap" between the inner and outer parts is "Between" refers to the area where a measurable space is formed between the inner and outer parts. In addition, even if a measurable space is not available, the opposing surfaces of the inner and outer parts can be This also includes the case where the gap is not physically or chemically bonded. This also includes the formation of microscopic spaces at part of the boundary between the inner and outer portions.

[0026] If the inner portion 26 is heated instead of the outer portion 24, the amount of thermal expansion of the inner portion 26 will be greater than that of the outer portion 24. Since the amount of thermal expansion of the inner portion 26 is larger than that of the outer portion 24, the amount of thermal expansion of the inner portion 26 and the outer portion 24 By pushing the interface outward, the cracks formed by the irradiation of the laser light are propagated. This causes new cracks to form at the interface. However, these cracks are located in the inner part. Since the inner portion 26 is pushed outward from the outer portion 24, it is difficult to form a gap at the interface between the inner portion 26 and the outer portion 24. Therefore, the heat of the heated inner portion 26 is transferred to the interface, and the formed cracks are re-solidified. It may not be possible to separate them reliably. In an embodiment, the heating of the outer portion 24 is higher than the heating of the inner portion 26 relative to the wire 22. This ensures that the gap is formed and that the separation caused by the crack formed using the laser is not thermally Therefore, re-adhesion can be prevented.

[0027] Another embodiment is a method for manufacturing a glass substrate having an aperture. The method is: (C) The surface of the glass plate that will become the glass substrate is irradiated with laser light in a roughly concentric pattern. forming an inner circular portion and an outer circular portion; (D) By heating the outer part of the outer circumferential circle, the outer part of the outer circumferential circle of the glass plate is turned into the outer circumferential circle. The outer circumferential portion is thermally expanded relative to the inner portion to form a gap. separating the inner portion from the outer portion of the outer circumferential portion; (E) By heating the outer part of the inner circumference, the outer part of the inner circumference of the glass plate becomes A gap is formed in the inner circumferential portion by thermal expansion, and the inner portion of the inner circumferential portion and the outer portion of the inner circumferential portion are and separating the components.

[0028] Another embodiment is a method for manufacturing a glass substrate having an aperture. The method is: (F) A laser beam is projected along a line forming a predetermined ring shape onto the surface of the raw glass plate that will become the glass substrate. irradiating to form a line defect; (G) Of the outer and inner parts of the glass plate with the defect, the outer By increasing the heating of the outer and inner parts of the glass plate, A separating step includes simultaneously heating the outer portion from both sides of the main surface of the glass plate; By heating the outer part more than the inner part, the outer part and the inner part of the glass plate and removing the inner portion as the portion that will become the opening.

[0029] FIG. 2 is a diagram illustrating heating of an outer portion in a method for manufacturing a glass substrate according to an embodiment. FIG. 2 shows the state after the inner circumferential portion described in (C) above is formed on the surface of the circular glass plate 30. Alternatively, a laser beam is irradiated onto the line having the predetermined ring shape described in (F) above, and the line is After forming the defect, separation by heating as described in (E) or (G) above is carried out. The raw glass plate 30 is a glass plate having a circular outer periphery formed on the surface thereof as described in (C) above. The inner portion of the outer circumferential circular portion and the outer portion of the outer circumferential circular portion are formed by carrying out the step (D) above. This is a board that has been separated and extracted. In the embodiment shown in FIG. 1, the inner and outer circumferential portions are the portions of the defect formed on the line 22. Therefore, the shape of the outer circumferential circular portion described above in (D) is the same as that of the raw glass plate 30 shown in FIG. corresponds to the outer shape of The outer portion 34 of the inner circumferential portion 32 formed by the irradiation of the laser beam is heated, and the glass element The outer portion 34 of the inner circumferential portion 32 of the plate 30 is thermally expanded relatively to form a gap at the inner circumferential portion 32. The inner portion 36 and the outer portion 34 are separated. As shown in (G) above, the outer portions 36 are removed from both sides of the main surface of the raw glass plate 30 at the same time. By heating the 34th minute, the amount of thermal expansion of the outer part of the outer circumferential part during heating described above in (D) is The amount of thermal expansion of the outer portion of the inner circumferential portion 32 is smaller than that of the outer portion of the glass plate 30, and the amount of thermal expansion is approximately uniform in the thickness direction of the glass plate 30. This allows for a uniform gap to be formed in the thickness direction. Even if the gap is small, the inner portion 36 can be removed from the outer portion 34. , which corresponds to a defect formed along line 22 in the embodiment shown in FIG.

[0030] In the embodiment having the steps (C) to (E), the steps (F) and (G) may also be performed. Even in the embodiment having the step, the outer portion is heated to form the outer circumferential portion or The outer part of the inner circumference is thermally expanded relative to the inner part, creating a gap between the outer circumference and the inner circumference. Therefore, the interface formed by the cracks using the laser can be re-fixed by heat. This makes it possible to efficiently form a glass substrate having an opening. This can be done. The above-mentioned "approximately concentric circles" refers to the deviation of the center position of the outer circumferential circle from the center position of the inner circumferential circle. The amount is 20 μm or less, preferably 5 μm or less.

[0031] (Specific Description of Glass Substrate Manufacturing Method) A method for manufacturing a glass substrate and a method for manufacturing a magnetic disk according to an embodiment will be described in detail below. do. FIG. 3(a) is a perspective view of an example of a glass substrate for a magnetic disk manufactured in one embodiment. FIG. 3(b) is an example of a cross section of the outer end surface of the magnetic disk glass substrate shown in FIG. FIG.

[0032] The glass substrate 1 shown in FIG. 3(a) is a glass substrate for a magnetic disk. The glass substrate for magnetic disks is a thin, circular glass substrate. The glass substrate for magnetic disks is used for magnetic disks with a nominal diameter of 2.5 inches or 3.5 inches. The nominal diameter of the glass substrate for a magnetic disk is 2.5 inches. For example, the outer diameter is 65 mm, the center hole diameter is 20 mm to 25 mm, and the plate thickness is 0.3 to 0. In the case of a glass substrate for a magnetic disk with a nominal diameter of 3.5 inches, for example, the outer diameter is The diameter is 95 mm, the diameter of the central hole is 20 mm to 25 mm, and the plate thickness is 0.3 to 0.8 mm. A magnetic layer is formed on the main surface of a glass substrate 1 to form a magnetic disk.

[0033] The glass substrate 1 has a pair of main surfaces 11p and 12p, a side wall surface 11w formed on the outer peripheral end surface, The chamfered surfaces 11c and 12c are located between the side wall surface 11w and the main surfaces 11p and 12p, and the inner peripheral end surface The outer peripheral end surface is also formed in the same manner as the outer peripheral end surface, and the side wall surface and the main surface 11 are not shown. and a chamfered surface (not shown) interposed between 12p and 12p. The glass substrate 1 has a circular hole at the center thereof. The side wall surface 11w is a circular hole extending in the thickness direction of the glass substrate 1. The inclination angles of the chamfered surfaces 11c and 12c with respect to the main surfaces 11p and 12p are particularly The angle is not limited to 45°, for example. The boundary is not limited to shapes with edges as shown, but may be smoothly continuous. It may also have a curved surface.

[0034] Such a glass substrate 1 is formed by a glass substrate prepared in advance as shown in FIG. 1 or FIG. The glass substrate is cut out from the plates 20 and 30 using a laser beam. 10A and 10B are diagrams illustrating irradiation of laser light in the manufacturing method.

[0035] The raw glass plate 60 irradiated with the laser beam L shown in FIG. 4 is, for example, a glass plate formed by a floating method. Alternatively, it is a glass plate of a certain thickness produced by the down-draw method. The raw glass plate 60 may be formed by pressing the raw glass plate 60 using a mold. , grinding and polishing to the target thickness when it becomes the final product, a glass substrate for magnetic disks. The thickness is equal to the amount of removal, for example, several μm.

[0036] The laser light source 40 is a device that emits laser light L, and is, for example, a YAG laser or A solid-state laser such as an ND:YAG laser is used. The wavelength of the laser light is preferably in the range of 1030 nm to 1070 nm, for example. . The laser light L is a pulse laser, and in one embodiment, the pulse width of the laser light L is set to 1. 0 -12 The time required for the laser beam L to reach the glass at the focal point is less than 1 picosecond. This is preferable since excessive deterioration can be suppressed. The optical energy of the laser light L is adjusted appropriately according to the pulse width and the repetition frequency of the pulse width. It can be adjusted appropriately to provide excessive optical energy for the pulse width and repetition frequency. This makes the glass prone to excessive deterioration, and residues are likely to remain at the focal point.

[0037] According to one embodiment, the laser light source 40 splits the oscillated laser light into two beams. The two beams are arranged to intersect on the surface of the glass plate 60 or inside the glass plate 60. As shown in the figure, the laser beam L is tilted relative to the normal direction of the main surface of the raw glass plate 60, and the glass plate 6 By irradiating the laser beam L in this manner, a point on the line 62 of the raw glass plate 60 At this point, the intersections of the light beams are formed continuously along the thickness direction. The light energy is concentrated linearly along the depth direction, and a part of the glass plate 60 is converted into plasma. Holes or through holes can be formed. According to one embodiment, the laser light L is a pulsed light pulse that is generated successively at regular time intervals. A burst that generates multiple optical pulse groups intermittently, with each optical pulse group consisting of It is preferable to irradiate the glass plate 60 with a single pulse. Among these, it is also preferable to make the light energy of one pulse variable. An example of such irradiation with laser light L is disclosed in Japanese Patent No. 5959597.

[0038] In the irradiation of the laser light L by the laser light source 40, the laser light L is directed to the raw glass plate 60. While moving the laser beam relative to the object, the laser beam is projected onto a line that forms a predetermined ring shape. For example, forming an inner or outer circular portion on the raw glass plate 60 In the irradiation of the laser beam L, the glass plate 60 is not moved, but the laser beam L is moved. Alternatively, the raw material glass plate 60 may be moved without moving the laser beam L.

[0039] When holes are intermittently formed at discrete positions on the line 62 by irradiation with the laser light L, for example, Since cracks tend to form from this hole to the adjacent hole, a different type of laser beam is used. Even if the irradiation is not repeated along the line, the inner or outer circumference of the circle can be heated. In other words, the irradiation of the laser light L The defects formed by the above process are easily removed by heating the outer portion of the raw glass plate 60 while maintaining the defects. In particular, the outer portion can be heated by separating the glass blank from the inner portion. By simultaneously heating from both sides of the main surface of 60, the outer and inner portions can be more easily It can be separated.

[0040] Next, the outer and inner portions of the glass plate 60 are separated by the line where the defect has formed, either by heating the outer portion more than the inner portion or by heating the outer portion. Figure 5 is a diagram specifically illustrating the heating of the glass plate 60 in one embodiment of the glass substrate manufacturing method. For example, when heating the glass plate 60, the outer portion 64 is placed in the heating space between the heaters 50 and 52, and the inner portion 66 is placed outside the heating space, relative to the line 62 where the defect has formed in the glass plate 60. This allows the outer portion 64 to be heated. Since the outer portion 64 is heated to a higher degree than the inner portion 66, the amount of thermal expansion of the outer portion 64 can be made greater than the amount of thermal expansion of the inner portion 66. As a result, the outer portion 64 thermally expands outward as shown in Figure 5. Therefore, a thermal expansion occurs at the interface between the outer portion 64 and the inner portion 66. Ensure gaps are formed Therefore, the separation of the outer portion 64 and the inner portion 66 can be ensured.

[0041] In the example shown in FIGS. 4 and 5, the laser light L is irradiated along a ring-shaped line to remove the defect. After forming the wire, the outer portion 64 of the wire is heated. The laser beam L is irradiated onto the raw material plate 60 along two different substantially concentric arcs, After forming the two defect portions, the outer circumferential portion 62a and the inner circumferential portion 62b, the outer circumferential portion 62a The outer portion of the inner circumferential portion 62b can also be heated. 3A to 3C are diagrams illustrating irradiation of laser light in the glass substrate manufacturing method of the embodiment.

[0042] In this way, when separating the outer portion 64 and the inner portion 66, the temperature of the outer portion 64 is made higher than the temperature of the inner portion 66, so that the outer portion 64 is separated from the inner portion 66. 66 By thermally expanding the glass plate relatively to the glass substrate and forming a gap along the line 62, the outer portion 64 and the inner portion 66 are separated, so that the portion to become the glass substrate can be reliably extracted from the glass plate. In particular, after forming the inner circular portion 62b, the outer portion of the inner circular portion 62b is heated simultaneously from both sides of the main surface of the glass plate 60, thereby uniforming the amount of thermal expansion along the thickness of the glass plate 60 and forming a uniform gap. In particular, since the inner circular portion 62b is closer to the center of the glass plate 60, its thermal expansion is smaller than that of the outer circular portion 62a, even when heated to the same degree as the outer portion of the outer circular portion 62a. Therefore, it is preferable to accurately form a gap that allows the portion that will become the glass substrate to be removed from the glass plate. Therefore, it is preferable to simultaneously heat the outer portion of the inner circular portion 62b from both sides of the main surface of the glass plate 60 to uniformly uniform the amount of thermal expansion along the thickness.

[0043] The glass substrate 1 has a ring shape with an opening. When manufacturing the ring-shaped structure, the shape of the outer edge of the ring-shaped structure having the opening is set to the shape of the line 62 (see FIG. 4). Defects are formed by irradiation with laser light L, and then the outer portion 64 (first outer portion) is heated. The first heating treatment may be performed to heat the inner portion 66 (first inner portion) to a higher temperature than the inner portion 66 (first inner portion). The surface of the outer peripheral edge face forming the outer edge of the glass substrate 1 by the laser beam L is preferably The roughness is smaller than that of the outer peripheral end surface mechanically cut using a conventional scriber, for example, The requirements for the outer cross section of the glass substrate for the magnetic disk in the hard disk drive device Since the surface roughness required is met, there is no need to polish the end face. The polishing time is short, so the outer edge shape of the glass substrate 1 can be formed efficiently. do. In this case, the glass plate 60 has a margin relative to the ring shape of the glass substrate 1 as follows: The outer portion 64 (first outer portion) and the inner portion 65 (second outer portion) are separated by a length of 0.1% to 5% of the outer diameter of the annular shape. It is preferable that the first inner portion 66 is separated from the first inner portion 66. The amount of lath blank 60 that is discarded increases, resulting in waste. In addition, the heat generated during heating spreads due to thermal conduction. This increases the heating time required to achieve the desired thermal expansion, which is problematic in terms of productivity. Not desirable.

[0044] When forming an opening (inner hole) in the glass substrate 1, the shape of the inner edge of the ring-shaped opening is indicated by a line 6. The shape of the second outer portion 64 is formed by irradiating the second outer portion 64 with a laser beam L. The heating of the inner portion 66 (the side portion) is made higher than that of the inner portion 66 (the second inner portion). It is preferable to perform the process as follows. The surface roughness of the inner peripheral edge surface is higher than that of the outer peripheral edge surface mechanically cut using a conventional scriber. For example, the magnetic disk guide that comes into contact with the rotating shaft in a hard disk drive device In order to satisfy the surface roughness required for the inner peripheral surface of the glass substrate, it is necessary to polish the edge. Therefore, even if the edge is polished, the polishing time is short. The holes can be formed efficiently.

[0045] In this case, it is preferable to carry out the second heat treatment after the first heat treatment. The inner portion 66 when the first heat treatment is performed becomes the outer portion 64 when the second heat treatment is performed. In the heat treatment, the inner portion 66 is not heated or is heated less than the outer portion 64. However, the inner portion 66 is heated by heat conduction from the outer portion 64, which has been heated. Therefore, the inner portion 66 whose temperature has risen is used as the outer portion 64 in the second heat treatment. When heating the material, the heating time required to cause a predetermined amount of thermal expansion can be shortened. In this way, the glass substrate 1 can be produced efficiently.

[0046] The laser beam L is irradiated onto the raw glass plate 60 at a plurality of discrete points on a line by the pulsed laser beam. After forming point-like through holes, a laser beam different from the pulsed laser beam is used to form linearly spaced holes. The irradiation position may be moved continuously along a line so as to connect the scattered points. In this case, among the plurality of through holes formed by the pulsed laser beam, cracks are present between adjacent through holes. A latent crack is formed, and then a different type of laser beam is used to remove the crack or the visible crack. The cracks formed can be connected between the through holes, so the glass substrate can be efficiently repaired in a short time. For example, a CO2 laser can be used as a different type of laser beam. This laser beam creates a linear defect that connects the intermittently formed defects. A recess can be formed. That is, defects are intermittently formed at discrete positions on the line 62 by irradiating the laser light L. Then, a CO2 laser is used as a different type of laser beam to connect the intermittently formed defects. By forming a linear defect as shown above, it is possible to form a crack reliably. This ensures that the outer and inner parts can be separated by heating.

[0047] The heating of the glass plate 60 after irradiation with the laser beam L is performed by heating the main surface of the glass plate 60. The main surfaces of both sides of the raw glass plate 60 are heated by radiant heat from heating sources provided on both sides of the surface. In the case of heating by radiation, heat is conducted from the main surface of the raw glass plate 60. The temperature of the raw glass plate 60 rises due to heat transfer from the outer portion 64 to the inner portion 66. The interface between the two does not heat up enough to rebond. A gap can be formed at the interface.

[0048] The ratio of the area of the main surface of the raw glass plate 60 to the area of the main surface of the glass substrate 1 is 1 01% to 160%, and when separating the outer portion 64 and the inner portion 66, one glass element It is preferable to extract one glass substrate 1 from the plate 60. When multiple glass substrates 1 are extracted from the glass substrate 60, the thickness of the glass substrate 60 varies depending on the location. This results in a large difference in thickness between individual glass substrates 1. Since it is preferable to make the thickness of the glass substrate uniform, the degree of grinding and polishing of the main surface of the glass substrate is It is complicated to adjust the distance between the glass substrates. In addition to being able to irradiate laser light, the outer part can be heated to separate the outer part from the inner part. Therefore, the handling of the raw glass plate 60 is improved. Using small glass plates 60, one inner part is taken from one glass plate 60. It is preferable to extract the glass substrate 1 from the viewpoint of the efficiency of manufacturing the glass substrate 1. When one glass plate is extracted from the glass plate 60, the entire outer surface of the large glass plate 60 is heated. When the glass sheet is removed from the heated area, the temperature of the outer and inner parts Since the temperature remains high, the outer part is heated to reach the specified thermal expansion amount. The temperature during heating becomes high, which is undesirable.

[0049] In one embodiment, the thickness of the raw glass plate 60 is 0.6 mm or less. The glass substrate 1 made from the lath blank 60 can be effectively used as a glass substrate for a magnetic disk. By reducing the thickness of the glass substrate for magnetic disks, it is possible to increase the storage capacity. To meet this demand, the number of magnetic disks installed in a hard disk drive must be increased. Furthermore, the raw glass plate 60 having a thickness of 0.6 mm or less is extremely thin and can be easily irradiated with laser, processed, and The glass is prone to cracking during the heat treatment to separate the outer and inner parts. The advantage of this embodiment is that the glass substrate can be reliably separated from the base plate. This is even greater in glass plates.

[0050] The glass substrates that have been shaped in this way are then processed in various ways to give them properties suitable for the final product. The process is carried out.

[0051] In this way, the outer peripheral end surface and the inner peripheral end surface (the outer peripheral end surface) of the glass substrate are removed from the raw glass plate 60. Chamfering of the corners formed by the main surface and the end faces (the interfaces between the side portions 64 and the inner portions 66) According to one embodiment, the corners are chamfered using a different type of laser beam L. This laser beam is used to chamfer the corners at an angle of 30 to 60 degrees relative to the main surface. The corners are heated and softened by irradiation from an oblique angle, causing evaporation. For example, a CO2 laser can be suitably used. By chamfering the surface, it is possible to form a chamfered surface with low surface roughness and high roundness. In this way, the corners formed by the inner peripheral end face or the outer peripheral end face and the main surface are formed by laser beam. Since the corners are chamfered with a laser beam, they can be easily chamfered with a grinding stone, etc. This method has higher production efficiency than when chamfering is performed. The corners of the glass substrate are cut out from the raw glass plate 60. Since no end surface polishing is required until the chip is removed, production efficiency is improved.

[0052] The main surfaces of the obtained glass substrate 1 are subjected to grinding and polishing treatment. In the grinding and polishing process, the glass substrate 1 is ground and then polished. In the grinding process, a double-sided grinding machine equipped with a planetary gear mechanism is used to grind the main surface of the glass substrate 1. Specifically, the outer peripheral end surface of the glass substrate 1 is ground by a grinding machine. The main surfaces of both sides of the glass substrate 1 are ground while the glass substrate 1 is held in a holding hole provided in the material. The grinding device has a pair of upper and lower surface plates (upper and lower surface plates). The glass substrate 1 is sandwiched between the upper and lower surface plates. The glass substrate 1 and each surface plate are moved relative to each other while supplying coolant. By moving the grinding tool, both main surfaces of the glass substrate 1 can be ground. The grinding member, which is a sheet of fixed abrasive grains fixed with resin, is attached to the surface plate and grinding is performed. It can be understood.

[0053] Next, the main surfaces of the ground glass substrate 1 are subjected to a first polishing. While holding the outer peripheral end surface of the polishing plate 1 in a holding hole provided in a polishing carrier of a double-side polishing machine, The main surfaces of both sides of the lath blank are polished. The first polishing removes the residual SiO2 remaining on the main surfaces after the grinding process. It aims to remove scratches and distortions, or adjust minute surface irregularities (micro waviness, roughness). The target.

[0054] In the first polishing process, a double-sided grinding machine having the same configuration as that used in the above-mentioned grinding process using fixed abrasive grains is used. The glass substrate 1 is polished while applying polishing slurry using a double-side polishing machine equipped with the above-mentioned. In the first polishing process, a polishing slurry containing loose abrasive grains is used. For example, abrasive grains such as cerium oxide or zirconia are used as the polishing agent. In the same manner as in the double-side grinding apparatus, the glass substrate 1 is sandwiched between a pair of upper and lower surface plates. The top surface of the upper surface of the upper surface plate and the bottom surface of the upper surface plate are provided with a flat polishing pad (e.g., a resin pad) having an overall circular shape. Then, either the upper or lower surface plate, or By moving both of them, the glass substrate 1 and each surface plate are moved relative to each other. The size of the polishing abrasive grains is 0.05 mm in average grain size (D50). It is preferable that the thickness is in the range of 0.5 to 3 μm.

[0055] After the first polishing, the glass substrate 1 may be chemically strengthened. In this case, the chemical strengthening liquid may be, for example, For example, a mixed melt of potassium nitrate and sodium sulfate is used, and the glass substrate 1 is immersed in a chemical strengthening liquid. This causes a compressive stress layer to form on the surface of the glass substrate 1 through ion exchange. It is possible.

[0056] Next, the glass substrate 1 is subjected to a second polishing process. The second polishing process is performed to mirror-polish the main surfaces. In the second polishing, a double-sided polishing machine having the same configuration as that used in the first polishing is used. Specifically, the outer peripheral edge of the glass substrate 1 is polished by the polishing tool of the double-side polishing machine. While being held in a holding hole provided in a carrier, the main surfaces on both sides of the glass substrate 1 are polished. In the second polishing process, the type and particle size of the free abrasive grains are changed compared to the first polishing process. The hardness of the resin polisher is different. For example, a polishing solution containing colloidal silica as free abrasive grains has both The polishing pad of the surface polishing device is supplied between the main surface of the glass substrate 1, and the main surface of the glass substrate 1 is polished. The size of the abrasive grains used in the second polishing is 5 to 50 in average grain size (d50). It is preferably in the range of nm. Whether or not chemical strengthening treatment is necessary may be appropriately determined in consideration of the glass composition and other requirements. In addition to the first and second polishing treatments, another polishing treatment may be performed. The above polishing processes may be performed in one polishing process. That's fine. In this way, the main surfaces of the glass substrate 1 are polished to the required polishing condition for a glass substrate for a magnetic disk. A glass substrate for a magnetic disk that satisfies the conditions can be obtained. After that, at least a magnetic layer is formed on the glass substrate 1 whose main surface is polished. A magnetic disk is fabricated.

[0057] Before the first polishing, for example, after the first grinding and before the first polishing, the glass substrate 1 is Alternatively, before the first grinding, an edge polishing process for polishing the edge surfaces of the glass substrate 1 may be performed. Even when such an end face polishing process is performed, the laser beam is used to polish the glass substrate 60. The arithmetic mean roughness Ra of the edge surface of the extracted glass substrate 1 is less than 0.01 μm, and the roundness is 15 Since the size is less than 1 μm, the time required for the end face polishing process is short. The end face polishing process is a polishing brush process in which loose abrasive grains are supplied to the end face while polishing with a polishing brush. Alternatively, a polishing method using a magnetic functional fluid may be used. The polishing method using a magnetic functional fluid is, for example, a method of using a slurry containing abrasive grains in a magnetic rheological fluid. The glass substrate 1 is then inserted into the mass by a magnetic field. The end face is polished by rotating the two parts relative to each other.

[0058] However, in order to improve production efficiency, it is preferable not to perform the end face polishing process. In the grinding and polishing process of the main surface, the roundness of the glass substrate 1 extracted from the raw glass plate 60 and further, while maintaining the surface roughness of at least a part of the cut surface, The surface is ground or polished.

[0059] The composition of the glass substrate 1 is not limited, but may be the following: It is preferable that Specifically, converted to an oxide standard, and expressed in mole percent, SiO2 is 50 to 75%, Al2O 3, 1 to 15% of at least one component selected from Li2O, Na2O and K2O At least 5 to 35% in total of selected from MgO, CaO, SrO, BaO and ZnO Also, one kind of component is contained in a total of 0-20%, as well as ZrO2, TiO2, La2O3, Y2O3 , Ta2O5, Nb2O5 and HfO2 in total of 0 The glass is an amorphous aluminosilicate glass with a composition containing 10% to 10% of SiO 2 .

[0060] The glass substrate 1 preferably contains, for example, 57 to 75% SiO2 in mass %. , 5 to 20% Al2O3 (however, the total amount of SiO2 and Al2O3 must be 74% or more), ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2 Total: over 0% but not more than 6%, Li2O over 1% but not more than 9%, Na2O 5-28% (However, the mass ratio of Li2O / Na2O is 0.5 or less), K2O is 0-6%, MgO is 0- 4%, CaO is more than 0% and 5% or less (however, the total amount of MgO and CaO is 5% or less) The CaO content is higher than the MgO content), SrO+BaO is 0-3%, Alternatively, the glass may be amorphous aluminosilicate glass having a composition as follows:

[0061] The composition of the glass substrate 1 is, as essential components, SiO2, Li2O, Na2O, and One or more alkaline earth metals selected from the group consisting of MgO, CaO, SrO and BaO The content of CaO relative to the total content of MgO, CaO, SrO and BaO is The molar ratio of the amount (CaO / (MgO+CaO+SrO+BaO)) is 0.20 or less The glass substrate 1 having such a composition may have a glass transition temperature of 650° C. or higher. Suitable for magnetic disk glass substrates used in magnetic disks for energy-assisted magnetic recording is.

[0062] The method for manufacturing a glass substrate and a method for manufacturing a magnetic disk according to the present invention have been described in detail above. However, the manufacturing method of the glass substrate and the manufacturing method of the magnetic disk of the present invention are not limited to the above-mentioned embodiment. The present invention is not limited to the above, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course. [Explanation of symbols]

[0063] 1. Glass substrate 11p,12p Main surface 11c,12c Chamfered surface 11w side wall 20, 30, 60 glass blanks 22,62 line 24,34,64 outer part 26,36,66 Inner part 32,62b Inner circumference circle 40 Laser light source 50,52 heater 62a Outer circular part

Claims

1. A glass substrate having a pair of main surfaces and an outer peripheral edge surface, The outer peripheral end surface is circular, A plurality of defects extending in the plate thickness direction are formed intermittently along the circumferential direction on the outer peripheral end surface, The arithmetic mean roughness Ra of the outer peripheral end surface is less than 0.01 μm, The glass substrate has an outer peripheral edge surface with a circularity of 15 μm or less.

2. A glass substrate having a pair of main surfaces, an outer peripheral edge surface, and an inner peripheral edge surface, The inner peripheral end surface is circular, A plurality of defects extending in the plate thickness direction are formed intermittently along the circumferential direction on the inner peripheral end surface, The arithmetic mean roughness Ra of the inner peripheral end surface is less than 0.01 μm, The glass substrate has an inner peripheral edge surface with a circularity of 15 μm or less.

3. A glass substrate having a pair of main surfaces, an outer peripheral edge surface, and an inner peripheral edge surface, the outer peripheral end surface and the inner peripheral end surface each have a circular shape, A plurality of defects extending in a plate thickness direction are formed intermittently along a circumferential direction on each of the outer peripheral end surface and the inner peripheral end surface, The arithmetic mean roughness Ra of the outer peripheral end surface and the inner peripheral end surface is less than 0.01 μm, The glass substrate has a circularity of 15 μm or less for each of the outer peripheral end face and the inner peripheral end face.

4. A glass substrate having a pair of main surfaces, an outer peripheral edge surface, and an inner peripheral edge surface, the outer peripheral end surface and the inner peripheral end surface each have a wall surface substantially perpendicular to the main surface and form a circle; The outer peripheral end surface and the inner peripheral end surface each have defects formed discretely at spaced apart locations on the end surface, the arithmetic mean roughness Ra of at least one of the outer peripheral end face and the inner peripheral end face is less than 0.01 μm; The glass substrate, wherein the circularity of at least one of the outer peripheral end face and the inner peripheral end face is 15 μm or less.

5. The outer peripheral end surface and the inner peripheral end surface are both circular, 5. The glass substrate according to claim 3, wherein the deviation between the center position of the circle formed by the outer peripheral edge surface and the center position of the circle formed by the inner peripheral edge surface is 20 [mu]m or less.

6. A glass substrate described in any one of claims 1 to 5, wherein the defect is formed by irradiation with laser light.

7. A glass substrate described in any one of claims 1 to 6, wherein the defect penetrates the pair of main surfaces in the thickness direction of the plate.

8. A method for manufacturing a glass substrate having a pair of main surfaces and an opening, comprising the steps of: a step of intermittently irradiating a surface of a raw glass plate that is a base for the glass substrate with a laser beam at discrete positions on each of substantially concentric lines on an outer circumferential portion and an inner circumferential portion, thereby forming holes or defects on each of the lines; heating an outer portion of the line of the outer circumferential circle to thermally expand the outer portion of the line of the outer circumferential circle of the glass plate relative to the inner portion of the line of the outer circumferential circle, thereby forming a gap in the line of the outer circumferential circle and separating the inner portion of the line of the outer circumferential circle from the outer portion of the line of the outer circumferential circle; heating an outer portion of the line of the inner circumferential circle to relatively thermally expand the outer portion of the line of the inner circumferential circle of the glass plate, forming a gap at the line of the inner circumferential circle, and separating the inner portion of the line of the inner circumferential circle from the outer portion of the line of the inner circumferential circle; Equipped with The thickness of the glass plate is 0.6 mm or less, a plurality of defects extending in the plate thickness direction and intermittently along the circumferential direction are formed on the outer peripheral edge surface of the glass substrate extracted from the raw glass plate, the arithmetic mean roughness Ra of the outer peripheral edge surface is less than 0.01 μm, and the roundness of the outer peripheral edge surface is 15 μm or less; A method for manufacturing a glass substrate comprising the steps of:

9. A method for manufacturing a glass substrate for a magnetic disk, comprising at least a process of polishing the pair of main surfaces of the glass substrate according to any one of claims 1 to 8.

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