JP6395453B2 - Glass plate manufacturing method and glass plate polishing apparatus - Google Patents

Description

  The present invention relates to a glass plate manufacturing method and a glass plate polishing apparatus.

  The glass plate is cut into a desired size in the manufacturing process. For example, the manufacturing process of glass substrates for flat panel displays such as liquid crystal displays and plasma displays, glass substrates for touch panels, and protective glass substrates forms marking lines on a large glass plate called mother glass. And cutting. A fine crack or a very sharp edge is usually formed on the cut surface of the glass plate. For the purpose of removing the edge formed on the cut surface, the cut surface is chamfered. For example, the cut surface is chamfered so that the cross section has an R shape. The chamfered cut surface is further finished into a mirror surface by polishing using a polishing wheel.

  Patent Document 1 (International Publication No. 2012/0667587) discloses a technique using a magnetic fluid for polishing an end face of a glass plate. In polishing processing using magnetic fluid, a magnetic fluid containing abrasive grains is held between a pair of magnets, and the end surface of the glass plate and the magnetic fluid are relative to each other while the end surface of the glass plate is in contact with the magnetic fluid. The end surface of the glass plate is polished by moving to. In the polishing process using a magnetic fluid, the magnetic fluid follows the shape of the workpiece and the polishing process is performed. Therefore, damage to the workpiece is relatively small. Therefore, when a polishing wheel that holds a magnetic fluid is used for polishing the end face of the glass plate, a smoother end face can be obtained as compared with a polishing process that uses a polishing wheel containing diamond abrasive grains.

  However, in the conventional polishing wheel that holds the magnetic fluid, the density of the magnetic flux existing in the space around the pair of magnets is low, and the holding force of the magnetic fluid is not sufficient. Therefore, the conventional polishing wheel has a problem that the polishing efficiency of the end face of the glass plate is low, and it takes a very long time to obtain an end face of a desired quality. Therefore, it is required to increase the density of magnetic flux existing in the space around the pair of magnets of the polishing wheel to increase the holding power of the magnetic fluid and improve the polishing efficiency of the glass plate.

  The objective of this invention is providing the manufacturing method of the glass plate which can improve the grinding | polishing efficiency of the end surface of a glass plate, and the polishing apparatus of a glass plate.

  The method for producing a glass plate according to the present invention includes rotating a magnetic material grain held in a magnetic field formed by a first magnetic field forming member and a second magnetic field forming member together with the first magnetic field forming member and the second magnetic field forming member. While rotating around, the end of the glass plate is brought into contact with the magnetic abrasive grains to polish the end. In this glass plate manufacturing method, the magnetic flux concentrating member concentrates the magnetic flux from the first magnetic field forming member to the second magnetic field forming member, thereby increasing the density of the magnetic flux. The magnetic flux concentration member is a magnetic body attached to the first magnetic field forming member and the second magnetic field forming member. In this method of manufacturing a glass plate, the end of the glass plate is brought into contact with magnetic abrasive grains held in a space where the magnetic flux density is increased by the magnetic flux concentrating member.

  This glass plate manufacturing method is a method in which an end surface of a glass plate is polished by bringing it into contact with magnetic abrasive grains rotated around a rotating shaft. The magnetic abrasive grains are held by a magnetic field formed by the first magnetic field forming member and the second magnetic field forming member. The magnetic flux concentrating member is provided so as to increase the magnetic flux density by concentrating the magnetic flux in at least a part of the space where the magnetic abrasive grains are held. In the space where the magnetic flux density is increased by the magnetic flux concentrating member, the holding force of the magnetic abrasive grains by the first magnetic field forming member and the second magnetic field forming member is larger than the holding force in the other spaces. The higher the holding power of the magnetic abrasive grains, the more difficult the magnetic abrasive grains move when the end face of the glass plate contacts the magnetic abrasive grains. As a result, the polishing pressure applied to the end surface of the glass plate by the rotating magnetic abrasive grains increases, and the ability to polish the end surface of the glass plate also increases. Therefore, this glass plate manufacturing method can improve the polishing efficiency of the end face of the glass plate.

  Further, in this glass plate manufacturing method, the space between the first magnetic field forming member and the second magnetic field forming member, and the space radially outside the rotating shaft of the first magnetic field forming member and the second magnetic field forming member. In at least one of the above, the magnetic flux density is preferably increased by the magnetic flux concentrating member.

  In this glass plate manufacturing method, magnetic lines of force that pass from the first magnetic field forming member to the second magnetic field forming member and pass through the space where the magnetic abrasive grains are held pass through the magnetic flux concentrating member. In addition, a magnetic flux concentrating member is provided. Thereby, the density of magnetic flux increases in the space in which the magnetic abrasive grains in contact with the end face of the glass plate are held. Therefore, this glass plate manufacturing method can improve the polishing efficiency of the end face of the glass plate.

  Moreover, in this glass plate manufacturing method, the space on the opposite side to the side where the second magnetic field forming member is located with respect to the first magnetic field forming member, and the side where the first magnetic field forming member is located with respect to the second magnetic field forming member Preferably, the magnetic flux density is increased by the magnetic flux concentrating member in at least one of the spaces on the opposite side.

  In this glass plate manufacturing method, magnetic lines of force that pass from the first magnetic field forming member to the second magnetic field forming member and pass through the space where the magnetic abrasive grains are held pass through the magnetic flux concentrating member. In addition, a magnetic flux concentrating member is provided. Thereby, the density of magnetic flux increases in the space in which the magnetic abrasive grains in contact with the end face of the glass plate are held. Therefore, this glass plate manufacturing method can improve the polishing efficiency of the end face of the glass plate.

  The polishing apparatus for a glass plate according to the present invention includes a rotating shaft, a first magnetic field forming member, a second magnetic field forming member, magnetic abrasive grains, and a magnetic flux concentrating member. The first magnetic field forming member is connected to the rotating shaft and rotates around the rotating shaft. The second magnetic field forming member is connected to the rotating shaft and rotates around the rotating shaft. The magnetic abrasive grains are held by a magnetic field formed by the first magnetic field forming member and the second magnetic field forming member. The magnetic flux concentration member is a magnetic body attached to the first magnetic field forming member and the second magnetic field forming member. A magnetic flux concentration member concentrates the magnetic flux which goes to a 2nd magnetic field formation member from a 1st magnetic field formation member, and increases the density of magnetic flux. The magnetic abrasive grains held in the space where the magnetic flux density is increased by the magnetic flux concentration member are rotated around the rotating shaft together with the first magnetic field forming member and the second magnetic field forming member, and the end of the glass plate Touch to polish the edge.

  Further, in this glass plate polishing apparatus, the magnetic flux concentrating member includes a space between the first magnetic field forming member and the second magnetic field forming member, and a rotating shaft of the first magnetic field forming member and the second magnetic field forming member. It is preferable to increase the magnetic flux density in at least one of the radially outer spaces.

  In this glass plate polishing apparatus, it is preferable that the magnetic flux concentrating member is attached at least radially outside the rotating shaft of the first magnetic field forming member and the second magnetic field forming member and has a magnetic flux concentrating groove. The magnetic flux concentrating groove is a groove formed at a right angle to the central axis of the rotating shaft on the radially outer surface of the rotating shaft of the magnetic flux concentrating member.

  In this glass plate polishing apparatus, the end surface of the glass plate is polished in contact with magnetic abrasive grains held in the space inside the magnetic flux concentration groove formed in the magnetic flux concentration member. The magnetic flux concentration member is provided so that the magnetic flux density in the space inside the magnetic flux concentration groove is increased.

  In this glass plate polishing apparatus, it is preferable that the magnetic flux concentrating member is further attached to each of the first magnetic field forming member and the second magnetic field forming member in the central axis direction of the rotating shaft.

  In this glass plate polishing apparatus, the magnetic flux concentrating member is a magnetic line of force that passes from the first magnetic field forming member to the second magnetic field forming member and passes through the magnetic flux concentrating groove. Provided. Thereby, the density of the magnetic flux in a magnetic flux concentration groove increases. Therefore, this glass plate manufacturing apparatus can improve the polishing efficiency of the end face of the glass plate. Note that the magnetic flux concentration member may be provided between the first magnetic field forming member and the second magnetic field forming member.

  Moreover, in this glass plate polishing apparatus, the first magnetic field forming member is preferably adjacent to the second magnetic field forming member in the central axis direction of the rotating shaft.

  In the glass plate polishing apparatus, the first magnetic field forming member and the second magnetic field forming member preferably have a cylindrical shape with the same dimensions. Moreover, it is preferable that the central axis of a 1st magnetic field formation member and a 2nd magnetic field formation member exists on the central axis of a rotating shaft. Moreover, it is preferable that the distance between the point in the radial direction innermost side of the rotating shaft of the magnetic flux concentrating groove and the central axis of the rotating shaft is equal to the outer diameters of the first magnetic field forming member and the second magnetic field forming member. .

  In this glass plate polishing apparatus, when viewed along the central axis of the rotating shaft, the deepest point of the magnetic flux concentration groove is at the same position as the outer peripheral surfaces of the first magnetic field forming member and the second magnetic field forming member.

  In this glass plate polishing apparatus, the magnetic flux concentrating member preferably increases the magnetic flux density in the space inside the magnetic flux concentrating groove.

  The glass plate manufacturing method and the glass plate polishing apparatus according to the present invention can improve the polishing efficiency of the end face of the glass plate.

It is a flowchart of the manufacturing method of the glass plate which concerns on this embodiment. It is a schematic diagram of the apparatus which performs from the melting process of FIG. 1 to a cutting process. It is the schematic of a grinding | polishing apparatus. It is an external view of a grinding wheel. It is sectional drawing of a grinding | polishing wheel. It is a part of sectional drawing of a grinding wheel. It is a figure showing the magnetic field which a grinding wheel forms. It is sectional drawing of the grinding | polishing wheel as a 1st comparative example. It is a figure showing the magnetic field which the grinding wheel as the 1st comparative example forms. It is sectional drawing of the grinding | polishing wheel as a 2nd comparative example. It is a figure showing the magnetic field which the grinding wheel as the 2nd comparative example forms. 6 is a cross-sectional view of a polishing wheel of Modification A. FIG. It is a figure showing the magnetic field which the grinding wheel of modification A forms. 6 is a cross-sectional view of a polishing wheel of Modification B. FIG. 10 is a part of a cross-sectional view of a polishing wheel of Modification B. FIG. It is a figure showing the magnetic field which the grinding wheel of modification B forms. 10 is a cross-sectional view of a polishing wheel of Modification C. FIG. 10 is a part of a cross-sectional view of a polishing wheel of Modification C. FIG. It is a figure showing the magnetic field which the grinding wheel of modification C forms. 10 is a cross-sectional view of a polishing wheel of Modification D. FIG. 10 is a part of a cross-sectional view of a polishing wheel of Modification E. FIG. 10 is a part of a cross-sectional view of a polishing wheel of Modification F. FIG. 10 is a part of a cross-sectional view of a grinding wheel of Modification G. FIG.

  The manufacturing method of the glass plate as embodiment of this invention is demonstrated referring drawings. The manufacturing method of the glass plate in this embodiment includes the method of grind | polishing the end surface of the glass plate manufactured using the overflow downdraw method.

(1) Overview of glass plate manufacturing method First, an overview of a glass plate manufacturing method will be described. The glass plate manufactured by this manufacturing method includes a glass substrate for a flat panel display (FPD) such as a liquid crystal display, a plasma display, and an organic EL display, a glass substrate for a touch panel, a glass substrate for a solar cell panel, and protection. It is used as a glass substrate for use. The glass plate has a thickness of, for example, 0.2 mm to 0.8 mm, and has dimensions of 680 mm to 2200 mm in length and 880 mm to 2500 mm in width. The glass plate has, for example, the following compositions (a) to (j).

(A) SiO ₂ : 50% by mass to 70% by mass,
(B) Al ₂ O ₃ : 10% by mass to 25% by mass,
(C) B ₂ O ₃ : 5% by mass to 18% by mass,
(D) MgO: 0% by mass to 10% by mass,
(E) CaO: 0% by mass to 20% by mass,
(F) SrO: 0% by mass to 20% by mass,
(G) BaO: 0% by mass to 10% by mass,
(H) RO: 5% by mass to 20% by mass (R is at least one selected from Mg, Ca, Sr and Ba),
(I) R ′ ₂ O: 0% by mass to 2.0% by mass (R ′ is at least one selected from Li, Na and K),
(J) At least one metal oxide selected from SnO ₂ , Fe ₂ O ₃ and CeO ₂ .

  Next, the manufacturing process of the glass plate using the overflow downdraw method will be described. FIG. 1 is an example of a flowchart showing a glass plate manufacturing process. The glass plate manufacturing process mainly includes a melting process (step S10), a clarification process (step S20), a stirring process (step S30), a forming process (step S40), a slow cooling process (step S50), It consists of a cutting process (step S60), a grinding process (step S70), and a polishing process (step S80). FIG. 2 is a schematic diagram of the glass plate manufacturing apparatus 100 that performs the melting step S10 to the cutting step S60. The glass plate manufacturing apparatus 100 includes a melting apparatus 101, a clarification apparatus 102, a stirring apparatus 103, a forming apparatus 104, and a cutting apparatus 105.

  In the melting step S10, the glass raw material is melted by the melting device 101 by heating means such as a burner, and a high-temperature molten glass 90 at 1500 ° C. to 1600 ° C. is generated. The glass raw material is prepared so that a glass having a desired composition can be substantially obtained. Here, “substantially” means that the presence of other trace components is allowed in the range of less than 0.1% by mass.

In the clarification step S20, the molten glass 90 is clarified by further raising the temperature of the molten glass 90 generated in the melting step S10 by the clarification device 102. In the clarification apparatus 102, the temperature of the molten glass 90 is raised to 1600 ° C to 1750 ° C, preferably 1650 ° C to 1700 ° C. In the clarification apparatus 102, fine bubbles of O ₂ , CO ₂ and SO ₂ contained in the molten glass 90 grow by absorbing O ₂ generated by reduction of a clarifier such as SnO ₂ contained in the glass raw material, It floats on the liquid surface of the molten glass 90 and disappears.

  In the stirring step S30, the molten glass 90 clarified in the clarification step S20 is stirred by the stirring device 103, and is chemically and thermally homogenized. In the stirring device 103, the molten glass 90 is stirred by a rotating shaft stirrer while flowing in the vertical direction, and sent to a downstream process from an outlet provided at the bottom of the stirring device 103. In the stirring step S <b> 30, glass components having a specific gravity different from the average specific gravity of the molten glass 90 such as zirconia-rich molten glass 90 are removed from the stirring device 103.

  In the forming step S40, the glass ribbon 91 is formed by the forming apparatus 104 from the molten glass 90 stirred in the stirring step S30 by the overflow down draw method. Specifically, the molten glass 90 overflowing and diverting from the upper part of the forming cell flows downward along the side wall of the forming cell and joins at the lower end of the forming cell, whereby the glass ribbon 91 is continuously formed. The molten glass 90 is cooled to a temperature suitable for molding by the overflow downdraw method, for example, 1200 ° C. before flowing into the molding step S40.

  In the slow cooling step S50, the glass ribbon 91 continuously generated in the molding step S40 is gradually cooled by the molding apparatus 104 to a temperature below the annealing point while temperature is controlled so as not to generate distortion and warpage.

  In the cutting step S60, the glass ribbon 91 that has been gradually cooled to room temperature in the slow cooling step S50 is cut into predetermined lengths by the cutting device 105. When the glass ribbon 91 is cut, a scribe line is formed on the glass ribbon 91, and the tensile stress is concentrated on the scribe line to cleave the glass ribbon 91. The scribe line is generally formed by a method of mechanically forming using a diamond cutter and a method of causing an initial crack to proceed by heating and rapid cooling using a laser. In the cutting step S60, the glass ribbon 91 cut into predetermined lengths is further cut into predetermined dimensions to obtain a glass plate 92.

  In grinding process S70, the corner | angular part of the glass plate 92 obtained by cutting process S60 is ground, and the end surface of the glass plate 92 is chamfered. A very sharp edge is formed at the corner between the end surface of the glass plate 92 cut in the cutting step S60 and the main surface. In the grinding step S70, the edge formed at the corner is removed by grinding the corner of the glass plate 92 using a diamond wheel or the like. The cross-sectional shape of the end surface of the glass plate 92 chamfered by grinding is an R shape.

  In the grinding step S70, the end surface of the glass plate 92 is ground so that the processing width of the end surface of the glass plate 92 is within a predetermined range. The processing width is the maximum value of the distance between the outermost end of the chamfered end surface of the glass plate 92 and the boundary between the end surface and the main surface. During the chamfering process, the force that the end surface of the glass plate 92 receives from the diamond wheel or the like gradually decreases from the outermost end of the end surface toward the boundary between the end surface and the main surface. Therefore, when the processing width is too large, the region near the boundary between the end surface of the glass plate 92 and the main surface is not sufficiently ground, and the end surface may not be processed uniformly. On the other hand, when the processing width is too small, the edges formed at the corners of the glass plate 92 may not be sufficiently removed. When the thickness of the glass plate 92 is t, the predetermined range of the processing width is preferably 1/50 t to t, more preferably 1/20 t to 1/2 t, and 1/10 t to 1 More preferably, it is / 3t. In the grinding step S70, the end surface of the glass plate 92 is ground so that the arithmetic average roughness Ra of the end surface of the glass plate 92 is 0.1 μm to 0.2 μm.

  On the end face of the glass plate 92 chamfered in the grinding step S70, a layer containing micro cracks called micro cracks or horizontal cracks is formed. This layer is called a work-affected layer or a brittle fracture layer. When the work-affected layer is formed, the breaking strength of the end face of the glass plate 92 is lowered. In the grinding step S70, the end surface of the glass plate 92 is ground so that the thickness of the work-affected layer is less than 3 μm.

  More specifically, the grinding step S70 includes a first grinding step and a second grinding step. In the first grinding process, a grinding wheel (metal bond diamond wheel or the like) hardened with a metal binder is used. In the second grinding step, a grinding wheel (resin bond diamond wheel or the like) hardened with a resin binder is used. In the second grinding process, a grinding wheel having lower hardness and rigidity than the grinding wheel used in the first grinding process is used. In the first grinding step, the required R shape is formed on the end surface of the glass plate 92 in a short time. In the second grinding step, the processing is performed in a short time so as to reduce the surface roughness of the end surface while adjusting the shape of the end surface of the glass plate 92.

  In the polishing step S80, the end surface of the glass plate 92 chamfered in the grinding step S70 is polished. The polishing step S80 is performed in order to further remove the work-affected layer and improve the breaking strength of the end face of the glass plate 92.

  After the polishing step S80, a cleaning step and an inspection step for the glass plate 92 are performed. Finally, the glass plate 92 is packed and shipped to an FPD manufacturer or the like. The FPD manufacturer manufactures an FPD by forming a semiconductor element such as a TFT on the surface of the glass plate 92.

(2) Details of Polishing Process Next, the polishing process for the end surface 92a of the glass plate 92 performed in the polishing process S80 will be described. In the polishing step S80, the end surface 92a of the glass plate 92 is polished by the polishing apparatus 10. FIG. 3 is a schematic view of the polishing apparatus 10. The polishing apparatus 10 polishes the pair of end surfaces 92 a along the long side of the glass plate 92 while conveying the glass plate 92.

  As shown in FIG. 3, the polishing apparatus 10 mainly includes a transport mechanism 12 and a polishing mechanism 14. The transport mechanism 12 transports the glass plate 92 along the long side of the glass plate 92. The transport mechanism 12 transports the glass plate 92 using a belt conveyor, a vacuum float panel, or the like. The vacuum float panel is a device that stably floats the glass plate 92 by blowing air to the lower surface of the glass plate 92 and sucking air from the space below the glass plate 92. The polishing mechanism 14 is installed on both sides of the glass plate 92 so as to face each of the pair of end surfaces 92 a of the glass plate 92. The polishing mechanism 14 has a polishing wheel 20. The polishing mechanism 14 presses the rotating polishing wheel 20 toward the end surface 92 a of the glass plate 92 to polish the end surface 92 a of the glass plate 92. In FIG. 3, the direction in which the glass plate 92 is conveyed and the direction in which the polishing wheel 20 rotates are indicated by arrows.

(2-1) Configuration of Polishing Wheel Next, the configuration of the polishing wheel 20 will be described. In the following description, the “conveying direction” means the long side direction of the glass plate 92, that is, the longitudinal direction of the end surface 92 a of the glass plate 92 and the direction in which the glass plate 92 is conveyed by the conveying mechanism 12. The “width direction” means a direction along the surface of the glass plate 92 and orthogonal to the transport direction. “Vertical direction” means a direction perpendicular to the surface of the glass plate 92. In the drawing, the conveyance direction is indicated by “y-axis”, the width direction is indicated by “x-axis”, and the vertical direction is indicated by “z-axis”. A plane perpendicular to the vertical direction is referred to as a “horizontal plane”. The surface of the glass plate 92 is parallel to the horizontal plane.

  The polishing wheel 20 is used for polishing the end surface 92 a of the glass plate 92. FIG. 4 is an external view of the polishing wheel 20. FIG. 5 is a cross-sectional view of the grinding wheel 20 cut along an xz plane including the central axis 21 a of the rotating shaft 21. FIG. 5 shows an end portion of the glass plate 92 to be polished by the polishing wheel 20 as a reference. The end surface 92a of the glass plate 92 is chamfered in an R shape as shown in FIG. The polishing wheel 20 mainly includes a rotating shaft 21, a first magnetic field forming member 22, a second magnetic field forming member 23, a polishing slurry 24, and a magnetic flux concentration member 25.

(2-1-1) Rotating shaft The rotating shaft 21 is a shaft for rotating the grinding wheel 20. The grinding wheel 20 rotates around the central axis 21 a of the rotating shaft 21. The central axis 21a is parallel to the vertical direction. As shown in FIG. 3, the rotation direction of the polishing wheel 20 is a direction in which the glass plate 92 is moved in a direction opposite to the direction in which the glass plate 92 is conveyed. The rotating shaft 21 is formed of a non-magnetic stainless steel material such as SUS304 so that the magnetic flux does not concentrate on the rotating shaft 21. Hereinafter, the radial direction of the rotating shaft 21, that is, the direction orthogonal to the central axis 21 a of the rotating shaft 21 is referred to as “radial direction”. In addition, regarding two points on the straight line in the radial direction, the side having the longer point from the central axis 21a is referred to as “radially outer side”, and the side having the shorter point from the central axis 21a. It is called “radially inside”.

  The rotating shaft 21 is connected to a rotating shaft drive unit (not shown) and rotates around the central axis 21a at a desired rotation speed. The rotating shaft 21 is connected to a rotating shaft moving mechanism (not shown), and moves so as to approach and separate from the end surface 92 a of the glass plate 92.

(2-1-2) First Magnetic Field Forming Member As shown in FIG. 5, the first magnetic field forming member 22 includes a first central member 22a and a first annular magnet 22b. The first center member 22a is a cylindrical member having a through hole formed along the vertical direction. The first center member 22a is formed of a non-magnetic stainless steel material such as SUS304 so that the magnetic flux does not concentrate on the first center member 22a. The rotating shaft 21 penetrates the through hole of the first center member 22a. The first center member 22 a is fixed to the rotary shaft 21. The first annular magnet 22b is a cylindrical member having a through hole formed along the vertical direction. The first center member 22a is fitted in the through hole of the first annular magnet 22b. The first annular magnet 22b is a magnet such as a permanent magnet and an electromagnet that is magnetized in the vertical direction and has an N pole on the upper side and an S pole on the lower side. Hereinafter, the upper surface of the first annular magnet 22b is referred to as a first upper magnetic field forming surface 22c, and the lower surface of the first annular magnet 22b is referred to as a first lower magnetic field forming surface 22d.

(2-1-3) Second Magnetic Field Forming Member As shown in FIG. 5, the second magnetic field forming member 23 includes a second central member 23a and a second annular magnet 23b. The second center member 23a is a columnar member having a through hole formed along the vertical direction. The second central member 23a is formed of a non-magnetic stainless steel material such as SUS304 so that the magnetic flux does not concentrate on the second central member 23a. The rotating shaft 21 penetrates the through hole of the second central member 23a. The second center member 23 a is fixed to the rotating shaft 21. The second annular magnet 23b is a cylindrical member having a through hole formed along the vertical direction. The second center member 23a is fitted in the through hole of the second annular magnet 23b. The second annular magnet 23b is a magnet such as a permanent magnet and an electromagnet that is magnetized in the vertical direction and has an N pole on the upper side and an S pole on the lower side. Hereinafter, the upper surface of the second annular magnet 23b is referred to as a second upper magnetic field forming surface 23c, and the lower surface of the second annular magnet 23b is referred to as a second lower magnetic field forming surface 23d.

  The first magnetic field forming member 22 has the same dimensions as the second magnetic field forming member 23. As shown in FIG. 5, the first magnetic field forming member 22 is provided above the second magnetic field forming member 23 in the vertical direction. The first magnetic field forming member 22 is adjacent to the second magnetic field forming member 23. That is, the first lower magnetic field forming surface 22d is in contact with the second upper magnetic field forming surface 23c.

  The first magnetic field forming member 22 and the second magnetic field forming member 23 form a magnetic field in the surrounding space. Thereby, the grinding wheel 20 can form a magnetic field in the surrounding space. The first annular magnet 22b of the first magnetic field forming member 22 and the second annular magnet 23b of the second magnetic field forming member 23 both have an S pole on the upper side and an N pole on the lower side. A magnet may be used.

(2-1-4) Polishing slurry The polishing slurry 24 is a mixture of magnetic abrasive grains and liquid. The polishing slurry 24 is held in a magnetic field formed by the polishing wheel 20.

  The magnetic abrasive grains are abrasive grains for polishing a brittle material such as the glass plate 92. The magnetic abrasive grains are composed of magnetic particles such as iron oxide and ferrite. When ferrite is used as magnetic abrasive grains, no additives are required to prevent oxidation, or the amount of additives used to prevent oxidation is reduced, which prevents deterioration of magnetic abrasive grains over time. can do.

  The liquid mixed with the magnetic abrasive grains is, for example, water, hydrocarbons, esters, ethers, and hydrogen fluoride. The liquid mixed with the magnetic abrasive grains may be a liquid containing water as a main component and added with hydrocarbons, esters, ethers, hydrogen fluoride, and the like. The liquid mixed with the magnetic abrasive grains is preferably water. By using water, the temperature rise of the polishing slurry 24 during the polishing process of the glass plate 92 can be suppressed.

  In order to suppress aggregation of the magnetic abrasive grains, 0.5 wt% or less of a surfactant may be added to the polishing slurry 24. The surfactant is, for example, a fatty acid ester. Further, in order to suppress the composition change of the polishing slurry 24, less than 3.0 wt% propylene glycol may be added to the polishing slurry 24.

  As the magnetic abrasive grains of the polishing slurry 24, for example, carbonyl iron powder manufactured by BASF is used. Carbonyl iron powder is spherical and has a particle size distribution with a diameter of 1 μm to 8 μm. The polishing slurry 24 is prepared by appropriately mixing a surfactant, a rust inhibitor, a wetting agent, a thickener and water with the magnetic abrasive grains. Further, the polishing slurry 24 may be further mixed with a nonmagnetic slurry such as ceria, alumina and silica to improve the polishing power.

  The magnetic abrasive grains preferably have a maximum magnetic flux density of 1.0 T or more and a maximum permeability of 3.0 H / m or more. When the concentration of the magnetic abrasive grains contained in the polishing slurry 24 is less than 85%, the maximum magnetic flux density is preferably 1.3 T or more, and the maximum magnetic permeability is preferably 3.3 H / m or more. Is more preferably 1.6 T or more.

(2-1-5) Magnetic flux concentrating member As shown in FIG. 5, the magnetic flux concentrating member 25 includes an upper concentrating member 25a, a lower concentrating member 25b, a first side concentrating member 25c, and a second side concentrating member. It is comprised from the member 25d. Each member constituting the magnetic flux concentrating member 25 is formed of a ferromagnetic soft steel such as SUS430. In addition, each member which comprises the magnetic flux concentration member 25 has high rigidity, and may be shape | molded with the other material which is a ferromagnetic body. Further, when the liquid mixed with the magnetic abrasive grains of the polishing slurry 24 is water, the magnetic flux concentrating member 25 is preferably formed of a rust-resistant material such as stainless steel. The first magnetic field forming member 22 and the second magnetic field forming member 23 are covered with a magnetic flux concentrating member 25 except for a portion where the rotary shaft 21 protrudes in the vertical direction. The first magnetic field forming member 22 and the second magnetic field forming member 23 covered with the magnetic flux concentration member 25 have a cylindrical shape through which the rotary shaft 21 penetrates in the vertical direction. The magnetic flux concentrating member 25 is fixed to the rotary shaft 21. 6 is an enlarged view of the radially outer end of the cross-sectional view of the grinding wheel 20 shown in FIG. In FIG. 6, the polishing slurry 24 and the glass plate 92 are omitted.

  The upper concentration member 25a is provided so as to cover at least the upper surface (N pole) of the first annular magnet 22b. The lower concentration member 25b is provided so as to cover at least the lower surface (S pole) of the second annular magnet 23b. The first side concentration member 25 c covers the outer peripheral surface of the first magnetic field forming member 22. The second side concentration member 25 d covers the outer peripheral surface of the second magnetic field forming member 23. As shown in FIG. 5, the radially outer ends of the upper concentration member 25a, the lower concentration member 25b, the first side concentration member 25c, and the second side concentration member 25d are all in the same position in the radial direction. is there. As shown in FIG. 6, the upper surface of the first side concentrating member 25c is in contact with the lower surface on the radially outer side of the upper concentrating member 25a, and the lower surface of the second side concentrating member 25d is the diameter of the lower concentrating member 25b. It is in contact with the upper surface of the direction outside.

  As shown in FIG. 6, the first side concentration member 25c has a first side surface 25e and a first inclined surface 25f. The first side surface 25e is an outer peripheral surface of the first side portion concentration member 25c. The first inclined surface 25f is a plane that is inclined downward in the vertical direction from the lower end of the first side surface 25e toward the radially inner side. The point on the innermost radial direction of the first inclined surface 25 f coincides with the lower end of the outer peripheral surface of the first magnetic field forming member 22.

  As shown in FIG. 6, the second side concentration member 25d has a second side surface 25g and a second inclined surface 25h. The second side surface 25g is an outer peripheral surface of the second side concentration member 25d. The second inclined surface 25h is a plane that is inclined upward in the vertical direction from the upper end of the second side surface 25g toward the radially inner side. The point on the innermost radial direction of the second inclined surface 25 h coincides with the upper end of the outer peripheral surface of the second magnetic field forming member 23.

  The first magnetic field forming member 22 is adjacent to the second magnetic field forming member 23 in the vertical direction. Therefore, the most radially inner point of the first inclined surface 25f of the first side concentrating member 25c coincides with the innermost point of the second inclined surface 25h of the second side concentrating member 25d. As a result, a magnetic flux concentrating groove 26 is formed on the outer peripheral surface of the magnetic flux concentrating member 25 as shown in FIG. The magnetic flux concentration groove 26 is a V-shaped groove composed of the first inclined surface 25f and the second inclined surface 25h. A space inside the magnetic flux concentration groove 26, that is, a space between the first inclined surface 25 f and the second inclined surface 25 h is a magnetic flux concentration space 27. The magnetic flux concentration space 27 is a space where magnetic flux, which is a magnetic flux formed by the polishing wheel 20, concentrates. A magnetic circuit that is a closed circuit of magnetic lines of force, which is a virtual line representing the magnetic field, is formed by guiding the magnetic field in a desired direction by the magnetic flux concentrating member 25 made of a ferromagnetic material through which the magnetic field easily passes. The magnetic flux concentration space 27 is a space including a part of the magnetic circuit.

  The innermost point in the radial direction of the magnetic flux concentration space 27 coincides with the outermost point in the radial direction of the contact surface between the first magnetic field forming member 22 and the second magnetic field forming member 23. The polishing slurry 24 is held in the magnetic flux concentration space 27 by the magnetic field formed by the polishing wheel 20.

  In addition, each member which comprises the magnetic flux concentration member 25 may be shape | molded integrally. For example, the upper concentration member 25a and the first side concentration member 25c may be formed as an integral member, or the lower concentration member 25b and the second side concentration member 25d may be formed as an integral member. Good.

(2-2) Magnetic Field Formed by Polishing Wheel FIG. 7 is an enlarged view of the radially outer end of the cross-sectional view of the polishing wheel 20 shown in FIG. FIG. 7 shows magnetic field lines, which are virtual lines representing the magnetic fields formed by the first magnetic field forming member 22 and the second magnetic field forming member 23 of the grinding wheel 20. In FIG. 7, the polishing slurry 24 and the glass plate 92 are omitted. In FIG. 7, hatching shown in FIGS. 5 and 6 is omitted in order to make magnetic lines of force conspicuous.

  FIG. 7 shows lines of magnetic force directed from the north pole of the first annular magnet 22 b of the first magnetic field forming member 22 to the south pole of the second annular magnet 23 b of the second magnetic field forming member 23. In FIG. 7, for example, starting from the first upper magnetic field forming surface 22 c of the first magnetic field forming member 22, the space around the radially outer side of the first magnetic field forming member 22 and the second magnetic field forming member 23 is turned around. The lines of magnetic force reaching the second lower magnetic field forming surface 23d of the second magnetic field forming member 23 are shown.

  The magnetic flux concentration member 25 increases the magnetic flux density of the magnetic flux concentration space 27 in which the polishing slurry 24 is held. Specifically, the upper concentrating member 25a forms a magnetic line so that the magnetic lines that flow out (release) upward from the first upper magnetic field forming surface 22c form a magnetic circuit that goes radially outward through the upper concentrating member 25a. Lead. The upper concentrating member 25a prevents the magnetic field lines flowing upward from the first upper magnetic field forming surface 22c from leaking into the space above the upper concentrating member 25a. The first side concentrating member 25c guides the magnetic force lines so that the magnetic lines of force guided by the upper concentrating member 25a form a magnetic circuit in the first side concentrating member 25c toward the magnetic flux concentration space 27. The first side concentrating member 25c suppresses the magnetic lines of force guided by the upper concentrating member 25a from leaking into the radially outer space of the first side concentrating member 25c. The second side concentrating member 25d guides the lines of magnetic force so that the magnetic lines of force guided by the first side concentrating member 25c form a magnetic circuit in the second side concentrating member 25d toward the lower concentrating member 25b. . The second side concentrating member 25d suppresses the magnetic lines of force guided by the first side concentrating member 25c from leaking out into the radially outer space of the second side concentrating member 25d. The lower concentrating member 25b guides the magnetic lines of force so that the magnetic lines of force guided by the second side concentrating member 25d form a magnetic circuit directed radially inward through the lower concentrating member 25b. The lower concentrating member 25b prevents the magnetic lines of force guided by the second side concentrating member 25d from leaking into the space below the lower concentrating member 25b.

  Accordingly, as shown in FIG. 7, the magnetic flux concentrating member 25 has the second lower part without leaking part of the magnetic field lines flowing upward from the first upper magnetic field forming surface 22 c to the space around the grinding wheel 20. It can be guided to the magnetic field forming surface 23d. Thereby, a magnetic circuit with little leakage magnetic flux can be formed. Comparing the case where the magnetic flux concentration member 25 is provided and the magnetic field lines flow out to the magnetic flux concentration member 25 and the case where the magnetic field lines flow out to the surrounding space without the magnetic flux concentration member 25 being compared, in the former, the magnetic field (magnetic field lines) is When the magnetic field passes through the magnetic flux concentrating member 25 made of a ferromagnetic material that easily passes, the magnetic flux leaking into the space is reduced, and a magnetic circuit having a strong magnetomotive force is formed. On the other hand, in the latter, since the magnetic field leaks into the surrounding space, a magnetic circuit having a weak magnetomotive force is formed compared to the former. Therefore, the magnetic flux leakage of the magnetic circuit starting from the first upper magnetic field forming surface 22c, passing through the magnetic flux concentrating member 25 that is a ferromagnetic material, and reaching the second lower magnetic field forming surface 23d is small. . Therefore, the difference between the magnetic force represented by the magnetic field lines flowing upward from the first upper magnetic field forming surface 22 c and the magnetic force represented by the magnetic field lines passing through the magnetic flux concentration space 27 is small. Therefore, the magnetic flux concentrating member 25 is attached to the first magnetic field forming member 22 and the second magnetic field forming member 23, so that the magnetic flux concentrating space 27, that is, the space around the first magnetic field forming member 22 and the second magnetic field forming member 23. Has the effect of increasing the magnetic flux density.

  The polishing slurry 24 is held by the magnetic field in the magnetic flux concentration space 27 in which the magnetic flux density is increased by the magnetic flux concentration member 25. The polishing slurry 24 fills the magnetic flux concentration groove 26. As shown in FIG. 5, the polishing slurry 24 held in the magnetic flux concentration space 27 has a slurry surface 24a. The slurry surface 24 a is a radially outer surface of the polishing slurry 24 that fills the magnetic flux concentration groove 26. The higher the magnetic flux density in the magnetic flux concentration space 27 is, the higher the strength of the magnetic field in the magnetic flux concentration space 27 is, so the magnitude of the force that the magnetic abrasive grains contained in the polishing slurry 24 receive from the magnetic field in the magnetic flux concentration space 27 increases. . That is, the force by which the magnetic field formed by the first magnetic field forming member 22 and the second magnetic field forming member 23 holds the polishing slurry 24 is increased by the magnetic flux concentration member 25 in the magnetic flux concentration space 27. Accordingly, the magnetic flux concentrating member 25 can improve the holding force of the polishing slurry 24 by the polishing wheel 20.

(2-3) Operation of Polishing Device A step in which the polishing device 10 polishes the end surface 92a of the glass plate 92 in the polishing step S80 will be described. First, the glass plate 92 whose end is chamfered in an R shape is transported by the transport mechanism 12. The glass plate 92 conveyed along the conveyance direction gradually approaches the polishing wheel 20 of the polishing mechanism 14. The polishing mechanism 14 may be installed in advance so that the position of the pair of polishing wheels 20 matches the width of the glass plate 92. Further, the polishing mechanism 14 detects that the end surface 92a of the glass plate 92 is sufficiently close to the polishing wheel 20 or that the end surface 92a of the glass plate 92 is in contact with the polishing wheel 20 by a sensor or the like, and rotates the rotating shaft. The polishing wheel 20 rotating about the central axis 21 a of the 21 may be moved toward the end surface 92 a of the glass plate 92. As a result, as shown in FIG. 5, the end surface 92a of the glass plate 92 is inserted into the polishing slurry 24 from the slurry surface 24a. In a state where the end surface 92 a of the glass plate 92 is inserted into the polishing slurry 24, the glass plate 92 is transported in the transport direction by the transport mechanism 12. As a result, the rotating polishing wheel 20 and the end surface 92a of the glass plate 92 relatively move along the conveying direction while the end surface 92a of the glass plate 92 is in contact with the polishing slurry 24. The end surface 92 a of the glass plate 92 is polished by colliding with magnetic abrasive grains contained in the polishing slurry 24 rotating together with the polishing wheel 20. Note that the polishing wheel 20 is moved in the transport direction without moving the glass plate 92 in the transport direction, and the rotating polishing wheel 20 and the end surface 92a of the glass plate 92 are relatively moved along the transport direction. You may let them. Further, both the glass plate 92 and the polishing wheel 20 may be moved in the conveyance direction, and the rotating polishing wheel 20 and the end surface 92a of the glass plate 92 may be relatively moved along the conveyance direction.

  On the end surface 92a of the glass plate 92 ground in the grinding step S70, a layer containing micro cracks called micro cracks or horizontal cracks is formed. This layer is called a work-affected layer or a brittle fracture layer and has a thickness of less than 3 μm. In the grinding step S70, the first grinding step and the second grinding step described above are performed, and the quality of the end surface 92a of the glass plate 92 is controlled. The polishing wheel 20 polishes the end surface 92a of the glass plate 92 to remove the work-affected layer or the brittle fracture layer on the end surface 92a. The polishing wheel 20 preferably polishes the end surface 92a of the glass plate 92 so that the arithmetic average roughness Ra of the end surface 92a of the glass plate 92 is, for example, 10 nm or less.

(3) Features The glass plate manufacturing method according to this embodiment includes a polishing step S80 in which the end surface 92a of the glass plate 92 manufactured using the overflow downdraw method is brought into contact with the rotating polishing slurry 24 and polished. . The polishing slurry 24 containing the abrasive grains that are magnetic abrasive grains is a magnetic flux concentration groove formed on the outer peripheral surface of the magnetic flux concentration member 25 by the magnetic field formed by the first magnetic field forming member 22 and the second magnetic field forming member 23. 26 is held in a magnetic flux concentration space 27 inside 26. In the magnetic flux concentration space 27, the magnetic force formed by the first magnetic field forming member 22 and the second magnetic field forming member 23 increases the force that holds the polishing slurry 24 by the magnetic flux concentration member 25. The magnetic flux concentrating member 25 is configured so that the magnetic field lines flowing upward from the first upper magnetic field forming surface 22c of the first magnetic field forming member 22 reach the second lower magnetic field forming surface 23d of the second magnetic field forming member 23 before the polishing wheel. Leakage to the space around 20 is suppressed. That is, the magnetic flux concentrating member 25 constitutes a part of a magnetic circuit of magnetic lines of force that flow from the first upper magnetic field forming surface 22c toward the second lower magnetic field forming surface 23d. The magnetic flux concentrating member 25 guides the magnetic field lines to the magnetic flux concentrating space 27, thereby suppressing a decrease in magnetic flux density in the magnetic flux concentrating space 27. Therefore, the magnetic flux concentrating member 25 has an effect of increasing the magnetic flux density in the magnetic flux concentrating space 27 by being attached to the first magnetic field forming member 22 and the second magnetic field forming member 23.

  As described above, the magnetic flux concentration space 27 is a space in which a decrease in the magnetic flux density is suppressed by the magnetic flux concentration member 25, and is a space where the holding power of the polishing slurry 24 is high. Since the polishing wheel 20 holding the polishing slurry 24 and the end surface 92a of the glass plate 92 are relatively moved along the conveying direction, the end surface 92a is polished as the holding power of the polishing slurry 24 increases. When coming into contact with the slurry 24, the abrasive grains contained in the polishing slurry 24 are more difficult to move. Then, as the abrasive grains contained in the polishing slurry 24 are less likely to move, the pressure applied to the end surface 92a by the abrasive grains increases, so the ability of the polishing wheel 20 to polish the end face 92a of the glass plate 92 improves. Therefore, the glass plate manufacturing method according to the present embodiment uses the magnetic flux concentrating member 25 to increase the holding force of the polishing slurry 24 for polishing the end surface 92a of the glass plate 92, so that the end surface 92a of the glass plate 92 is formed. Polishing efficiency can be improved. In addition, since the glass plate manufacturing method according to the present embodiment can locally improve the magnetic flux density of the magnetic flux concentration space 27, the polishing slurry 24 can generate magnetic flux even if the end surface 92a of the glass plate 92 is continuously processed. Outflow and dispersion from the concentration groove 26 can be suppressed.

  Next, in order to explain the effect of the magnetic flux concentrating member 25 that increases the magnetic flux density in the magnetic flux concentrating space 27, two comparative examples for the polishing wheel 20 according to the present embodiment will be described. FIG. 8 is a cross-sectional view of a grinding wheel 120 as a first comparative example. FIG. 9 is a part of a cross-sectional view of a grinding wheel 120 as a first comparative example, and shows a magnetic field formed by the grinding wheel 120. FIG. 10 is a cross-sectional view of a polishing wheel 220 as a second comparative example. FIG. 11 is a part of a cross-sectional view of a grinding wheel 220 as a second comparative example, and is a diagram showing a magnetic field formed by the grinding wheel 220. 9 and 11, the polishing slurries 124 and 224 and the glass plate 92 are omitted. In FIGS. 9 and 11, hatching is omitted in order to make the lines of magnetic force stand out.

  In the first comparative example, the polishing wheel 120 mainly includes a rotating shaft 121, a first magnetic field forming member 122, a second magnetic field forming member 123, a polishing slurry 124, and a spacer 125. The rotating shaft 121, the first magnetic field forming member 122, the second magnetic field forming member 123, and the polishing slurry 124 are respectively the rotating shaft 21, the first magnetic field forming member 22, the second magnetic field forming member 23, and the polishing slurry 24 of the present embodiment. Since these are the same as those in FIG. The first magnetic field forming member 122 includes a first center member 122a and a first annular magnet 122b. The second magnetic field forming member 123 includes a second center member 123a and a second annular magnet 123b. The spacer 125 is a stainless steel plate that is sandwiched between the first magnetic field forming member 122 and the second magnetic field forming member 123 and through which the rotary shaft 121 passes. The spacer 125 has a cylindrical shape in which a hole through which the rotary shaft 121 passes is formed. The outer peripheral surface of the spacer 125 is radially inward from the outer peripheral surfaces of the first magnetic field forming member 122 and the second magnetic field forming member 123. Therefore, the polishing wheel 120 has a magnetic field forming groove 126 that is a gap between the first magnetic field forming member 122 and the second magnetic field forming member 123. The magnetic field forming groove 126 is a space between the first annular magnet 122 b of the first magnetic field forming member 122 and the second annular magnet 123 b of the second magnetic field forming member 123. The polishing slurry 124 is held in the groove space 127 inside the magnetic field forming groove 126.

  In the first comparative example, as shown in FIG. 9, the magnetic lines of force that flow upward from the upper surface of the first annular magnet 122 b are the spaces outside the radial direction of the first magnetic field forming member 122 and the second magnetic field forming member 123. And reaches the lower surface of the second annular magnet 123b. In the groove space 127, the lines of magnetic force flowing upward from the upper surface of the second annular magnet 123b flow toward the lower surface of the first annular magnet 122b.

  In the first comparative example, as shown in FIG. 9, the lines of magnetic force flow out to the space opposite to the groove space 127 with the first magnetic field forming member 122 and the second magnetic field forming member 123 interposed therebetween. For this reason, the magnetic flux leaking into the opposite space increases, so the magnetic flux density in the groove space 127 is small. Therefore, the magnetic flux density of the groove space 127 is smaller than the magnetic flux density of the magnetic flux concentration space 27 of the present embodiment.

  In the second comparative example, the polishing wheel 220 mainly includes a rotating shaft 221, a first magnetic field forming member 222, a second magnetic field forming member 223, and a polishing slurry 224. Since the rotating shaft 221 and the polishing slurry 224 are the same as the rotating shaft 21 and the polishing slurry 24 of this embodiment, respectively, description thereof is omitted. The first magnetic field forming member 222 includes a first center member 222a and a first annular magnet 222b. The second magnetic field forming member 223 includes a second central member 223a and a second annular magnet 223b. The first annular magnet 222b has an inclined surface that is inclined downward in the vertical direction from the outer peripheral surface thereof toward the radially inner side. The second annular magnet 223b has an inclined surface that is inclined upward in the vertical direction from the outer peripheral surface thereof toward the radially inner side. The respective inclined surfaces of the first annular magnet 222b and the second annular magnet 223b are magnetic field forming grooves 226 that are V-shaped grooves, like the first inclined surface 25f and the second inclined surface 25h of the present embodiment. Is forming. The magnetic field forming groove 226 is a space between the first annular magnet 222b and the second annular magnet 223b. The polishing slurry 224 is held in a groove space 227 that is a space inside the magnetic field forming groove 226.

  In the second comparative example, as shown in FIG. 11, the lines of magnetic force that flow upward from the upper surface of the first annular magnet 222b are the spaces outside the radial direction of the first magnetic field forming member 222 and the second magnetic field forming member 223. And reaches the lower surface of the second annular magnet 223b. In the groove space 227, the lines of magnetic force flowing upward from the upper surface of the second annular magnet 223b flow toward the lower surface of the first annular magnet 222b.

  In the second comparative example, as shown in FIG. 11, the magnetic field lines flow out to the space opposite to the groove space 227 with the first magnetic field forming member 222 and the second magnetic field forming member 223 interposed therebetween. For this reason, the magnetic flux leaking into the space on the opposite side increases, so the magnetic flux density in the groove space 227 is small. Therefore, the magnetic flux density of the groove space 227 is smaller than the magnetic flux density of the magnetic flux concentration space 27 of the present embodiment.

  As described above, in the first comparative example and the second comparative example, the polishing wheels 120 and 220 that are not covered with the ferromagnetic material are spaces in which the polishing slurry 24 is held as compared with the polishing wheel 20 of the present embodiment. The magnetic flux density is low and the holding power of the polishing slurry 24 is small. In the present embodiment, the magnetic flux concentration member 25 is provided so that the magnetic flux density of at least a part of the magnetic flux concentration space 27 in which the polishing slurry 24 is held increases. Therefore, the polishing apparatus 10 of the present embodiment uses the magnetic flux concentrating member 25 that is a ferromagnetic material to increase the holding force of the polishing slurry 24 that polishes the end surface 92a of the glass plate 92. The polishing efficiency of 92a can be improved.

(4) Modifications The glass plate manufacturing method in the present embodiment has been described above. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications are made without departing from the gist of the present invention. May be.

(4-1) Modification A
As shown in FIG. 5, the magnetic flux concentrating member 25 according to the present embodiment includes an upper concentrating member 25a, a lower concentrating member 25b, a first side concentrating member 25c, and a second side concentrating member 25d. Is done. However, the magnetic flux concentration member 25 may not include the upper concentration member 25a and the lower concentration member 25b.

  FIG. 12 is a cross-sectional view of the polishing wheel 320 of this modification. FIG. 13 is a part of a cross-sectional view of the grinding wheel 320 and shows a magnetic field formed by the grinding wheel 320. In FIG. 13, the polishing slurry 324 and the glass plate 92 are omitted. In FIG. 13, hatching is omitted in order to make the lines of magnetic force stand out.

  In this modification, the polishing wheel 320 mainly includes a rotating shaft 321, a first magnetic field forming member 322, a second magnetic field forming member 323, a polishing slurry 324, and a magnetic flux concentrating member 325. The rotating shaft 321, the first magnetic field forming member 322, the second magnetic field forming member 323, and the polishing slurry 324 are respectively the rotating shaft 21, the first magnetic field forming member 22, the second magnetic field forming member 23, and the polishing slurry 24 of the present embodiment. Since these are the same as those in FIG. The first magnetic field forming member 322 includes a first center member 322a and a first annular magnet 322b. The second magnetic field forming member 323 includes a second central member 323a and a second annular magnet 323b. The magnetic flux concentrating member 325 includes a first side concentrating member 325c and a second side concentrating member 325d. That is, the magnetic flux concentration member 325 has a configuration in which the upper concentration member 25a and the lower concentration member 25b are removed from the magnetic flux concentration member 25 of the present embodiment. As shown in FIG. 12, the magnetic flux concentrating member 325 has a magnetic field forming groove 326 that is a V-shaped groove formed on the outer peripheral surface thereof. The polishing slurry 324 is held in a magnetic flux concentration space 327 that is a space inside the magnetic field forming groove 326.

  In the present modification, as shown in FIG. 13, some of the lines of magnetic force that flow upward from the upper surface of the first annular magnet 322b are the first side concentration member 325c, the magnetic flux concentration space 327, and the second side concentration. The member passes through the member 325d in order and reaches the lower surface of the second annular magnet 323b. The magnetic field lines passing through the magnetic flux concentration space 327 pass through the magnetic flux concentration member 325 that is a ferromagnetic body that covers a part of the polishing wheel 320. Therefore, the magnetic flux concentrating member 325 guides the magnetic field lines flowing from the upper surface of the first annular magnet 322b toward the lower surface of the second annular magnet 323b to the magnetic flux concentrating space 327, so that the magnetic flux density in the magnetic flux concentrating space 327 increases. That is, the magnetic flux concentrating member 325 is attached to the first magnetic field forming member 322 and the second magnetic field forming member 323, thereby increasing the magnetic flux density of the magnetic flux concentrating space 327 and increasing the holding force of the polishing slurry 324 in the magnetic flux concentrating space 327. Has the effect of increasing.

  Therefore, the glass plate manufacturing method according to this modification uses the magnetic flux concentrating member 325 to increase the holding force of the polishing slurry 324 for polishing the end surface 92a of the glass plate 92. Polishing efficiency can be improved.

(4-2) Modification B
As shown in FIG. 5, the magnetic flux concentrating member 25 according to the present embodiment includes an upper concentrating member 25a, a lower concentrating member 25b, a first side concentrating member 25c, and a second side concentrating member 25d. Is done. However, the magnetic flux concentration member 25 may further include a spacer that is sandwiched between the first magnetic field forming member 22 and the second magnetic field forming member 23.

  FIG. 14 is a cross-sectional view of the polishing wheel 420 of this modification. FIG. 15 is a part of a sectional view of the grinding wheel 420. FIG. 16 is a part of a cross-sectional view of the grinding wheel 420 and shows a magnetic field formed by the grinding wheel 420. In FIGS. 15 and 16, the polishing slurry 424 and the glass plate 92 are omitted. In FIG. 16, hatching is omitted in order to make the lines of magnetic force stand out.

  In this modification, the polishing wheel 420 mainly includes a rotating shaft 421, a first magnetic field forming member 422, a second magnetic field forming member 423, a polishing slurry 424, and a magnetic flux concentrating member 425. Since the rotating shaft 421 and the polishing slurry 424 are the same as the rotating shaft 21 and the polishing slurry 24 of this embodiment, respectively, description thereof is omitted. The first magnetic field forming member 422 includes a first center member 422a and a first annular magnet 422b. The second magnetic field forming member 423 includes a second central member 423a and a second annular magnet 423b. The magnetic flux concentration member 425 includes an upper concentration member 425a, a lower concentration member 425b, a first side concentration member 425c, and a second side concentration member 425d. The magnetic flux concentration member 425 includes an intermediate member 425e between the first side concentration member 425c and the second side concentration member 425d. The intermediate member 425e is a steel plate such as stainless steel that is sandwiched between the first magnetic field forming member 422 and the second magnetic field forming member 423 and through which the rotary shaft 421 passes. The intermediate member 425e has a cylindrical shape in which a hole through which the rotary shaft 421 passes is formed. The outer peripheral surface of the intermediate member 425e is at the same position in the radial direction as the outer peripheral surfaces of the first magnetic field forming member 422 and the second magnetic field forming member 423. Note that the intermediate member 425e positioned between the first side concentration member 425c and the second side concentration member 425d is preferably a ferromagnetic body, and the first side concentration member 425c and the second side concentration member. It may be formed integrally with at least one of the members 425d.

  The first side concentration member 425c has a first side surface 425f and a first inclined surface 425g. The first side surface 425f is an outer peripheral surface of the first side concentration member 425c. The first inclined surface 425g is a plane that is inclined downward in the vertical direction from the lower end of the first side surface 425f toward the radially inner side. The most radially inner point of the first inclined surface 425g coincides with an intermediate point between the upper end and the lower end of the outer peripheral surface of the intermediate member 425e.

  The second side concentration member 425d has a second side surface 425h and a second inclined surface 425i. The second side surface 425h is an outer peripheral surface of the second side concentration member 425d. The second inclined surface 425i is a plane that is inclined upward in the vertical direction from the upper end of the second side surface 425h toward the inside in the radial direction. The most radially inner point of the second inclined surface 425i coincides with an intermediate point between the upper end and the lower end of the outer peripheral surface of the intermediate member 425e.

  The point on the innermost side in the radial direction of the first inclined surface 425g of the first side portion concentrating member 425c coincides with the point on the innermost side in the radial direction of the second inclined surface 425i of the second side portion concentrating member 425d. As a result, a magnetic flux concentrating groove 426 that is a V-shaped groove is formed on the outer peripheral surface of the magnetic flux concentrating member 425 as shown in FIG. The polishing slurry 424 is held in a magnetic flux concentration space 427 that is a space inside the magnetic field forming groove 426.

  In this modification, as shown in FIG. 16, some of the magnetic lines of force that flowed upward from the upper surface of the first annular magnet 422b are an upper concentration member 425a, a first side concentration member 425c, a magnetic flux concentration space 427, It passes through the second side concentration member 425d and the lower concentration member 425b in order, and reaches the lower surface of the second annular magnet 423b. The magnetic lines of force that have flowed upward from the upper surface of the second annular magnet 423b pass through the intermediate member 425e and reach the lower surface of the first annular magnet 422b. The magnetic field lines passing through the magnetic flux concentration space 427 pass through the magnetic flux concentration member 425 that is a ferromagnetic body that covers the polishing wheel 420. Therefore, the magnetic flux concentration member 425 is provided so that a magnetic circuit of magnetic lines of force that flows from the upper surface of the first annular magnet 422b toward the lower surface of the second annular magnet 423b is formed. The magnetic flux concentration member 425 increases the magnetic flux density in the magnetic flux concentration space 427 by guiding the magnetic field lines to the magnetic flux concentration space 427. That is, the magnetic flux concentrating member 425 is attached to the first magnetic field forming member 422 and the second magnetic field forming member 423 to increase the magnetic flux density of the magnetic flux concentrating space 427 and to increase the holding force of the polishing slurry 424 in the magnetic flux concentrating space 427. Has the effect of increasing.

  Therefore, the glass plate manufacturing method according to this modification uses the magnetic flux concentrating member 425 to increase the holding force of the polishing slurry 424 for polishing the end surface 92a of the glass plate 92. Polishing efficiency can be improved.

(4-3) Modification C
As shown in FIG. 5, the magnetic flux concentrating member 25 according to the present embodiment includes an upper concentrating member 25a, a lower concentrating member 25b, a first side concentrating member 25c, and a second side concentrating member 25d. Is done. However, the magnetic flux concentrating member 25 further includes a spacer sandwiched between the first magnetic field forming member 22 and the second magnetic field forming member 23, and does not include the upper concentrating member 25a and the lower concentrating member 25b. Also good.

  FIG. 17 is a cross-sectional view of the polishing wheel 520 of this modification. FIG. 18 is a part of a sectional view of the grinding wheel 520. FIG. 19 is a part of a cross-sectional view of the grinding wheel 520 and shows a magnetic field formed by the grinding wheel 520. 18 and 19, the polishing slurry 524 and the glass plate 92 are omitted. In FIG. 19, hatching is omitted in order to make the lines of magnetic force stand out. The grinding wheel 520 has a configuration in which the grinding wheel 320 of the modification A and the grinding wheel 420 of the modification B are combined.

  In this modification, the polishing wheel 520 mainly includes a rotating shaft 521, a first magnetic field forming member 522, a second magnetic field forming member 523, a polishing slurry 524, and a magnetic flux concentration member 525. Since the rotating shaft 521 and the polishing slurry 524 are the same as the rotating shaft 21 and the polishing slurry 24 of this embodiment, respectively, description thereof is omitted. The first magnetic field forming member 522 includes a first central member 522a and a first annular magnet 522b. The second magnetic field forming member 523 includes a second center member 523a and a second annular magnet 523b. The magnetic flux concentrating member 525 includes a first side concentrating member 525c and a second side concentrating member 525d. That is, the magnetic flux concentration member 525 has a configuration in which the intermediate concentration member 525e is added to the magnetic flux concentration member 25 of the present embodiment, and the upper concentration member 25a and the lower concentration member 25b are removed. The intermediate member 525e is a steel plate such as stainless steel that is sandwiched between the first magnetic field forming member 522 and the second magnetic field forming member 523 and through which the rotary shaft 521 passes. The intermediate member 525e has a cylindrical shape in which a hole through which the rotary shaft 521 passes is formed. The outer peripheral surface of the intermediate member 525e is at the same position in the radial direction as the outer peripheral surfaces of the first magnetic field forming member 522 and the second magnetic field forming member 523. Note that the intermediate member 525e positioned between the first side concentration member 525c and the second side concentration member 525d is preferably a ferromagnetic body, and the first side concentration member 525c and the second side concentration member 525c. It may be formed integrally with at least one of the members 525d.

  The first side concentration member 525c has a first side surface 525f and a first inclined surface 525g. The first side surface 525f is an outer peripheral surface of the first side concentration member 525c. The first inclined surface 525g is a plane that is inclined downward in the vertical direction from the lower end of the first side surface 525f toward the radially inner side. The point on the innermost side in the radial direction of the first inclined surface 525g coincides with an intermediate point between the upper end and the lower end of the outer peripheral surface of the intermediate member 525e.

  The second side concentrating member 525d has a second side surface 525h and a second inclined surface 525i. The second side surface 525h is an outer peripheral surface of the second side concentration member 525d. The second inclined surface 525i is a plane that is inclined upward in the vertical direction from the upper end of the second side surface 525h toward the radially inner side. The point on the innermost side in the radial direction of the second inclined surface 525i coincides with an intermediate point between the upper end and the lower end of the outer peripheral surface of the intermediate member 525e.

  The innermost point in the radial direction of the first inclined surface 525g of the first side concentration member 525c coincides with the innermost point in the radial direction of the second inclined surface 525i of the second side concentration member 525d. As a result, a magnetic flux concentrating groove 526 which is a V-shaped groove is formed on the outer peripheral surface of the magnetic flux concentrating member 525 as shown in FIG. The polishing slurry 524 is held in a magnetic flux concentration space 527 that is a space inside the magnetic field forming groove 526.

  In this modification, as shown in FIG. 19, some of the lines of magnetic force that flow upward from the upper surface of the first annular magnet 522b are part of the first side concentration member 525c, the magnetic flux concentration space 527, and the second side concentration. It passes through the member 525d in order and reaches the lower surface of the second annular magnet 523b. The magnetic lines of force that flowed upward from the upper surface of the second annular magnet 523b pass through the intermediate member 525e and reach the lower surface of the first annular magnet 522b. The magnetic field lines passing through the magnetic flux concentration space 527 pass through the magnetic flux concentration member 525 that is a ferromagnetic body that covers a part of the polishing wheel 520. Therefore, the magnetic flux concentration member 525 is provided so that a magnetic circuit of magnetic lines of force that flows from the upper surface of the first annular magnet 522b toward the lower surface of the second annular magnet 523b is formed. The magnetic flux concentration member 525 increases the magnetic flux density in the magnetic flux concentration space 527 by guiding the magnetic field lines to the magnetic flux concentration space 527. That is, the magnetic flux concentrating member 525 is attached to the first magnetic field forming member 522 and the second magnetic field forming member 523, thereby increasing the magnetic flux density of the magnetic flux concentrating space 527 and increasing the holding force of the polishing slurry 524 in the magnetic flux concentrating space 527. Has the effect of increasing.

  Therefore, the glass plate manufacturing method according to this modification uses the magnetic flux concentrating member 525 to improve the holding power of the polishing slurry 524 that polishes the end surface 92a of the glass plate 92, so that the end surface 92a of the glass plate 92 is improved. Polishing efficiency can be improved.

(4-4) Modification D
The magnetic flux concentration member 25 according to the present embodiment includes an upper concentration member 25a and a lower concentration member 25b. As shown in FIG. 5, the upper concentrating member 25a covers both the upper surface of the first central member 22a and the upper surface of the first annular magnet 22b, and the lower concentrating member 25b is the second central member 23a. And the lower surface of the second annular magnet 23b. However, the upper concentrating member 25a may not cover the upper surface of the first central member 22a, and the lower concentrating member 25b may not cover the lower surface of the second central member 23a.

  FIG. 20 is a cross-sectional view of the polishing wheel 20 of this modification. In FIG. 20, the components other than the upper concentration member 25a and the lower concentration member 25b are the same as those in the present embodiment. The upper concentration member 25a covers only the upper surface of the first annular magnet 22b of the first magnetic field forming member 22 and the upper surface of the first side concentration member 25c. The lower concentration member 25b covers only the lower surface of the second annular magnet 23b of the second magnetic field forming member 23 and the lower surface of the second side concentration member 25d.

  In the present modification, the magnetic field lines passing through the magnetic flux concentration space 27 pass through the magnetic flux concentration member 25 that is a ferromagnetic material that covers a part of the polishing wheel 20, as in FIG. 6 according to the present embodiment. Therefore, the magnetic flux concentrating member 25 is attached to the first magnetic field forming member 22 and the second magnetic field forming member 23, thereby increasing the magnetic flux density of the magnetic flux concentrating space 27 and increasing the holding power of the polishing slurry 24 in the magnetic flux concentrating space 27. Has the effect of increasing.

  Therefore, the glass plate manufacturing method according to this modification uses the magnetic flux concentrating member 25 to improve the holding power of the polishing slurry 24 that polishes the end surface 92a of the glass plate 92, so that the end surface 92a of the glass plate 92 is improved. Polishing efficiency can be improved.

  Note that the upper concentration member 25a and the lower concentration member 25b of the present modification can be applied to the modifications A to C.

  Further, the first central member 22a and the second central member 23a may be an integral member, and the first annular magnet 22b and the second annular magnet 23b may be an integral member.

(4-5) Modification E
The magnetic flux concentration member 25 according to the present embodiment includes a first side concentration member 25c and a second side concentration member 25d. A magnetic flux concentrating groove 26 that is a V-shaped groove is formed on the outer peripheral surface of the magnetic flux concentrating member 25. However, a groove having a shape other than the V shape may be formed on the outer peripheral surface of the magnetic flux concentration member 25.

  FIG. 21 is a part of a cross-sectional view of the polishing wheel 20 of this modification, corresponding to FIG. 6 of the present embodiment. In FIG. 21, the components other than the first side concentration member 25c and the second side concentration member 25d are the same as in the present embodiment.

  The first side concentrating member 25c has a first side surface 25e and a first curved surface 25f. The first side surface 25e is an outer peripheral surface of the first side portion concentration member 25c. The first curved surface 25f is a surface that is curved downward in the vertical direction from the lower end of the first side surface 25e toward the radially inner side. The point on the innermost radial direction of the first curved surface 25 f coincides with the lower end of the outer peripheral surface of the first magnetic field forming member 22.

  The second side concentration member 25d has a second side surface 25g and a second curved surface 25h. The second side surface 25g is an outer peripheral surface of the second side concentration member 25d. The second curved surface 25h is a surface curved upward in the vertical direction from the upper end of the second side surface 25g toward the radially inner side. The innermost point in the radial direction of the second curved surface 25 h coincides with the upper end of the outer peripheral surface of the second magnetic field forming member 23.

  As shown in FIG. 21, the most radially inner point of the first curved surface 25f of the first side concentrating member 25c is the innermost point of the second curved surface 25h of the second side concentrating member 25d. Matches. As a result, a magnetic flux concentrating groove 26 is formed on the outer peripheral surface of the magnetic flux concentrating member 25 as shown in FIG. The magnetic flux concentration groove 26 is a groove constituted by the first curved surface 25f and the second curved surface 25h. A magnetic flux concentration space 27 that is a space inside the magnetic flux concentration groove 26 is a space in which the polishing slurry 24 is held.

  In the present modification, the magnetic field lines passing through the magnetic flux concentration space 27 pass through the magnetic flux concentration member 25 that is a ferromagnetic material that covers a part of the polishing wheel 20, as in FIG. 6 according to the present embodiment. Therefore, the magnetic flux concentrating member 25 is attached to the first magnetic field forming member 22 and the second magnetic field forming member 23, thereby increasing the magnetic flux density of the magnetic flux concentrating space 27 and increasing the holding power of the polishing slurry 24 in the magnetic flux concentrating space 27. Has the effect of increasing.

  Therefore, the glass plate manufacturing method according to this modification uses the magnetic flux concentrating member 25 to improve the holding power of the polishing slurry 24 that polishes the end surface 92a of the glass plate 92, so that the end surface 92a of the glass plate 92 is improved. Polishing efficiency can be improved.

  In addition, the 1st side part concentration member 25c and the 2nd side part concentration member 25d of this modification are applicable to modification AD.

(4-6) Modification F
The magnetic flux concentration member 25 according to the present embodiment includes a first side concentration member 25c and a second side concentration member 25d. A magnetic flux concentrating groove 26 that is a V-shaped groove is formed on the outer peripheral surface of the magnetic flux concentrating member 25. The most radially inner point of the magnetic flux concentration groove 26 is on the outer peripheral surfaces of the first magnetic field forming member 22 and the second magnetic field forming member 23. However, the innermost point in the radial direction of the magnetic flux concentration groove 26 may not be on the outer peripheral surfaces of the first magnetic field forming member 22 and the second magnetic field forming member 23.

  FIG. 22 is a part of a cross-sectional view of the polishing wheel 20 of the present modification, corresponding to FIG. 6 of the present embodiment. In FIG. 22, the components other than the first side concentration member 25c and the second side concentration member 25d are the same as in this embodiment.

  The first side concentration member 25c has a first side surface 25e and a first inclined surface 25f. The first side surface 25e is an outer peripheral surface of the first side portion concentration member 25c. The first inclined surface 25f is a plane that is inclined downward in the vertical direction from the lower end of the first side surface 25e toward the radially inner side. The point on the innermost side in the radial direction of the first inclined surface 25 f is located on the outer side in the radial direction with respect to the lower end of the outer peripheral surface of the first magnetic field forming member 22.

  The second side concentrating member 25d has a second side surface 25g and a second inclined surface 25h. The second side surface 25g is an outer peripheral surface of the second side concentration member 25d. The second inclined surface 25h is a plane that is inclined upward in the vertical direction from the upper end of the second side surface 25g toward the radially inner side. The point on the innermost side in the radial direction of the second inclined surface 25 h is located on the outer side in the radial direction with respect to the upper end of the outer peripheral surface of the second magnetic field forming member 23.

  As shown in FIG. 22, the innermost point in the radial direction of the first inclined surface 25f of the first side concentrating member 25c is the innermost point in the radial direction of the second inclined surface 25h of the second side concentrating member 25d. Matches. As a result, a magnetic flux concentrating groove 26 is formed on the outer peripheral surface of the magnetic flux concentrating member 25 as shown in FIG. The innermost point in the radial direction of the magnetic flux concentration groove 26 is located on the outer side in the radial direction with respect to the outer peripheral surfaces of the first magnetic field forming member 22 and the second magnetic field forming member 23. A magnetic flux concentration space 27 that is a space inside the magnetic flux concentration groove 26 is a space in which the polishing slurry 24 is held.

  In this modification, the magnetic field lines passing through the magnetic flux concentration space 27 pass through the magnetic flux concentration member 25 that is a ferromagnetic body that covers the polishing wheel 20, as in FIG. 6 according to the present embodiment. Therefore, the magnetic flux concentrating member 25 is attached to the first magnetic field forming member 22 and the second magnetic field forming member 23, thereby increasing the magnetic flux density of the magnetic flux concentrating space 27 and increasing the holding power of the polishing slurry 24 in the magnetic flux concentrating space 27. Has the effect of increasing.

  Therefore, the glass plate manufacturing method according to this modification uses the magnetic flux concentrating member 25 to improve the holding power of the polishing slurry 24 that polishes the end surface 92a of the glass plate 92, so that the end surface 92a of the glass plate 92 is improved. Polishing efficiency can be improved.

  In addition, the 1st side part concentration member 25c and the 2nd side part concentration member 25d of this modification are applicable to modification AE.

(4-7) Modification G
The magnetic flux concentration member 425 according to Modification B includes a first side concentration member 425c and a second side concentration member 425d. A magnetic flux concentrating groove 426 that is a V-shaped groove is formed on the outer peripheral surface of the magnetic flux concentrating member 425. The point on the innermost radial direction of the magnetic flux concentration groove 426 is on the outer peripheral surfaces of the first magnetic field forming member 422 and the second magnetic field forming member 423. However, the innermost point in the radial direction of the magnetic flux concentration groove 426 may not be on the outer peripheral surfaces of the first magnetic field forming member 422 and the second magnetic field forming member 423.

  FIG. 23 is a part of a cross-sectional view of the grinding wheel 420 of this modification, corresponding to FIG. 15 of Modification B. In FIG. 23, the components other than the first side concentration member 425c and the second side concentration member 425d are the same as in the modification example B.

  The first side concentration member 425c has a first side surface 425f and a first inclined surface 425g. The first side surface 425f is an outer peripheral surface of the first side concentration member 425c. The first inclined surface 425g is a plane that is inclined downward in the vertical direction from the lower end of the first side surface 425f toward the radially inner side. The point on the innermost side in the radial direction of the first inclined surface 425g is located on the inner side in the radial direction from the lower end of the outer peripheral surface of the first magnetic field forming member 422.

  The second side concentration member 425d has a second side surface 425h and a second inclined surface 425i. The second side surface 425h is an outer peripheral surface of the second side concentration member 425d. The second inclined surface 425i is a plane that is inclined upward in the vertical direction from the upper end of the second side surface 425h toward the inside in the radial direction. The point on the innermost side in the radial direction of the second inclined surface 425 i is located on the inner side in the radial direction from the upper end of the outer peripheral surface of the second magnetic field forming member 423.

  As shown in FIG. 23, the innermost point in the radial direction of the first inclined surface 425g of the first side concentrating member 425c is the innermost point in the radial direction of the second inclined surface 425i of the second side concentrating member 425d. Matches. As a result, a magnetic flux concentrating groove 426 is formed on the outer peripheral surface of the magnetic flux concentrating member 425 as shown in FIG. The magnetic flux concentration groove 426 is a groove constituted by the first inclined surface 425g and the second inclined surface 425i. The point on the innermost radial direction of the magnetic flux concentrating groove 426 is located on the radially inner side of the outer peripheral surfaces of the first magnetic field forming member 422 and the second magnetic field forming member 423. A magnetic flux concentration space 427 that is a space inside the magnetic flux concentration groove 426 is a space in which the polishing slurry 424 is held.

  In the present modification, the magnetic field lines passing through the magnetic flux concentration space 427 pass through the magnetic flux concentration member 425 that is a ferromagnetic body that covers the polishing wheel 420, as in FIG. Therefore, the magnetic flux concentrating member 425 is attached to the first magnetic field forming member 422 and the second magnetic field forming member 423, thereby increasing the magnetic flux density of the magnetic flux concentrating space 427 and increasing the holding power of the polishing slurry 424 in the magnetic flux concentrating space 427. Has the effect of increasing.

  Therefore, the glass plate manufacturing method according to the present modification uses the magnetic flux concentrating member 425 to improve the holding power of the polishing slurry 424 for polishing the end surface 92a of the glass plate 92, so that the end surface 92a of the glass plate 92 is improved. Polishing efficiency can be improved.

  In addition, the 1st side part concentration member 425c and the 2nd side part concentration member 425d of this modification can be applied similarly to the modification C.

(4-8) Modification H
The polishing apparatus 10 according to this embodiment polishes the end surface 92a of the glass plate 92. However, the polishing apparatus 10 may polish the end face of other plate-like articles such as a metal plate and a ceramic plate.

(5) Example Next, the Example of the manufacturing method of the glass plate in this embodiment is described.

  The end surface 92a of the glass plate 92 was polished using the polishing apparatus 10 including the polishing wheel 20 according to the present embodiment. Then, the magnetic flux density at the innermost point in the radial direction of the end surface 92a was measured when the polishing wheel 20 was polishing the end surface 92a.

  Further, the polishing wheel 120 according to the first comparative example shown in FIG. 8, the polishing wheel 220 according to the second comparative example shown in FIG. 10, the polishing wheel 320 according to the modified example A shown in FIG. The same measurement was performed on the polishing wheel 420 according to Modification B shown in FIG. 5 and the polishing wheel 520 according to Modification C shown in FIG.

  In all the grinding wheels used in this example, the first magnetic field forming member and the second magnetic field forming member had an outer diameter of 125 mm, an inner diameter of 90 mm, and a vertical dimension of 10 mm.

  The following table shows the measurement results of this example. The unit of magnetic flux density measured is Tesla (T). As shown in the table, it was confirmed that the value of the magnetic flux density measured using the polishing wheel 20 according to this embodiment was the highest. The value of the magnetic flux density measured using the grinding wheel 20 according to the present embodiment, the grinding wheel 320 according to Modification A, the grinding wheel 420 according to Modification B, and the grinding wheel 520 according to Modification C is It was confirmed that the value was higher than the value of the magnetic flux density measured using the polishing wheel 120 according to the first comparative example and the polishing wheel 220 according to the second comparative example.

  The end surface 92a of the glass plate 92 was polished using the polishing apparatus 10 including the polishing wheel 420 according to Modification B. Then, the magnetic flux density at the innermost point in the radial direction of the end surface 92a when the polishing wheel 420 was polishing the end surface 92a was measured.

  Furthermore, the same measurement was performed for each of a plurality of types of polishing wheels in which the radial position of the innermost point is different from that of the polishing wheel 420 as in the polishing wheels according to the modification F and the modification G. . Here, the “innermost point” is a point on the innermost side in the radial direction of the magnetic flux concentration groove 426 formed on the outer peripheral surface of the magnetic flux concentration member 425 of the polishing wheel 420.

  The radial position of the innermost point is measured with reference to the radial position of the reference point. Here, the “reference point” is a point on the outer peripheral surface of the first magnetic field forming member 422 and the second magnetic field forming member 423. As shown in FIG. 22 according to the modified example F, when the innermost point is radially outside the reference point, the radial position of the innermost point is defined as having a positive value. As shown in FIG. 23 according to Modification G, when the innermost point is radially inward of the reference point, the radial position of the innermost point is defined as having a negative value.

  Further, the radial position of the innermost point is measured with the radial position of the reference point being zero. For example, when the radial position of the innermost point is “+1 mm”, the innermost point is 1 mm from the reference point toward the outer side in the radial direction, and the radial position of the innermost point is “−1 mm”. ”, The innermost point is located 1 mm radially inward from the reference point.

  In all the grinding wheels used in this example, the first magnetic field forming member and the second magnetic field forming member had an outer diameter of 125 mm, an inner diameter of 90 mm, and a vertical dimension of 10 mm.

  The following table shows the measurement results of this example. The unit of magnetic flux density measured is Tesla (T). As shown in the table, it was confirmed that the value of the magnetic flux density measured using the grinding wheel whose radial position at the innermost point is 0 mm, that is, the grinding wheel 420 according to the modified example B, is the highest. It was.

  The end surface 92a of the glass plate 92 was polished a plurality of times using the polishing wheel 20 according to the present embodiment, and the arithmetic average roughness Ra of the end surface 92a after polishing was measured.

  Moreover, the end surface 92a of the glass plate 92 was grind | polished several times using the grinding | polishing wheel 120 which concerns on a 1st comparative example, and arithmetic mean roughness Ra of the end surface 92a after grinding | polishing was measured.

  In all the grinding wheels used in this example, the first magnetic field forming member and the second magnetic field forming member had an outer diameter of 125 mm, an inner diameter of 90 mm, and a vertical dimension of 10 mm. The thickness of the glass plate 92 used in this example was 0.5 mm, the rotation speed of the polishing wheel was 2000 rotations per minute, and the conveyance speed of the glass plate 92 was 2400 mm per minute.

  The following table shows the measurement results of this example. When the end surface 92a of the glass plate 92 was polished using the polishing wheel 120 according to the first comparative example, the arithmetic average roughness Ra of the end surface 92a was 10 nm after the end surface 92a was polished six times. On the other hand, when the end surface 92a of the glass plate 92 was polished using the polishing wheel 20 according to the present embodiment, the arithmetic average roughness Ra of the end surface 92a was 10 nm after the end surface 92a was polished twice.

  As described above, in this example, the arithmetic average roughness Ra of the end surface 92a was 10 nm or less and the cracks (microcracks and horizontal cracks) were able to be removed from the end surface 92a by two polishing processes.

  Note that the end surface 92a before polishing was obtained by the following procedure. First, the glass plate 92 was cut into a predetermined size by mechanical scribing using a cutting wheel. Next, the end surface 92a which is a cut surface of the glass plate 92 was ground by a metal bond diamond wheel. Thereby, the required shape was formed in the end surface 92a in a short time. Next, the end face 92a was ground by a resin bond diamond wheel. As a result, processing was performed to reduce the surface roughness of the end surface 92a while adjusting the shape of the end surface 92a. By the above steps, an end face 92a having a work-affected layer of less than 3 μm was finally obtained.

  In these examples, the end surface 92a of the glass plate 92 cut by the laser was polished using the polishing wheel 20 of the present embodiment. The end surface 92a of the glass plate 92 cut by the laser had a corner portion having a substantially perpendicular cross section. On the other hand, the end surface 92a polished by the polishing wheel 20 has an end surface 92a having a R-shaped corner and a radius of curvature of less than 10 μm.

21 Rotating shaft 21a Central axis of rotating shaft 22 First magnetic field forming member 23 Second magnetic field forming member 24 Polishing slurry (magnetic abrasive)
25 Magnetic flux concentration member 26 Magnetic flux concentration groove 92 Glass plate 92a End surface of glass plate (end of glass plate)

International Publication No. 2012/066757

Claims (10)

In a state where the magnetic abrasive grains held in the magnetic field formed by the first magnetic field forming member and the second magnetic field forming member are rotated around the rotating shaft together with the first magnetic field forming member and the second magnetic field forming member , A method for producing a glass plate in which an end of a glass plate is brought into contact with a magnetic abrasive grain to polish the end,
The first magnetic field forming member has a first central member and a first annular magnet,
The first central member is a cylindrical member that is formed of a nonmagnetic material through which the rotating shaft passes.
The first annular magnet is a cylindrical member that is penetrated by the first central member and magnetized along the rotating shaft,
The second magnetic field forming member has a second central member and a second annular magnet,
The second central member is a cylindrical member that is formed of a nonmagnetic material through which the rotating shaft passes.
The second annular magnet is a cylindrical member that penetrates the second central member and is magnetized along the rotating shaft.
The end is polished in a polishing space ;
A magnetic flux concentrating member, which is a magnetic body that guides the lines of magnetic force flowing out from the first magnetic field forming member or the second magnetic field forming member to the polishing space, is attached to the first magnetic field forming member or the second magnetic field forming member . ,
Manufacturing method of glass plate. In at least one of a space between the first magnetic field forming member and the second magnetic field forming member, and a space radially outside the rotating shaft of the first magnetic field forming member and the second magnetic field forming member. , Increasing the magnetic flux density by the magnetic flux concentrating member,
The manufacturing method of the glass plate of Claim 1. A space opposite to the side where the second magnetic field forming member is located with respect to the first magnetic field forming member, and a space opposite to the side where the first magnetic field forming member is located with respect to the second magnetic field forming member. In at least one, the magnetic flux density is increased by the magnetic flux concentrating member,
The manufacturing method of the glass plate of Claim 2. A rotating shaft;
A first magnetic field forming member coupled to the rotating shaft and rotating around the rotating shaft;
A second magnetic field forming member coupled to the rotating shaft and rotating around the rotating shaft;
Magnetic abrasive grains held by a magnetic field formed by the first magnetic field forming member and the second magnetic field forming member;
A magnetic body that is attached to the first magnetic field forming member and the second magnetic field forming member, and concentrates the magnetic flux from the first magnetic field forming member toward the second magnetic field forming member to increase the density of the magnetic flux. A concentrated member;
With
The first magnetic field forming member has a first central member and a first annular magnet,
The first central member is a cylindrical member that is formed of a nonmagnetic material through which the rotating shaft passes.
The first annular magnet is a cylindrical member that is penetrated by the first central member and magnetized along the rotating shaft,
The second magnetic field forming member has a second central member and a second annular magnet,
The second central member is a cylindrical member that is formed of a nonmagnetic material through which the rotating shaft passes.
The second annular magnet is a cylindrical member that penetrates the second central member and is magnetized along the rotating shaft.
The magnetic abrasive grains held in the space where the magnetic flux density is increased by the magnetic flux concentrating member are rotating around the rotating shaft together with the first magnetic field forming member and the second magnetic field forming member. Polishing the edge in contact with the edge of the glass plate,
Glass plate polishing equipment. The magnetic flux concentrating member includes a space between the first magnetic field forming member and the second magnetic field forming member, and a radially outer side of the rotating shaft of the first magnetic field forming member and the second magnetic field forming member. Increasing the density of the magnetic flux in at least one of the spaces;
The glass plate polishing apparatus according to claim 4. The magnetic flux concentrating member is attached at least to the radially outer side of the rotary shaft of the first magnetic field forming member and the second magnetic field forming member, and has a magnetic flux concentrating groove,
The magnetic flux concentrating groove is a groove formed at a right angle to the central axis of the rotating shaft on the radially outer surface of the rotating shaft of the magnetic flux concentrating member.
The glass plate polishing apparatus according to claim 4 or 5. The magnetic flux concentration member is further attached to each of the first magnetic field forming member and the second magnetic field forming member and in the central axis direction of the rotating shaft.
The glass plate polishing apparatus according to claim 6. The first magnetic field forming member is adjacent to the second magnetic field forming member and the central axis direction of the rotating shaft,
The glass plate polishing apparatus according to claim 6 or 7. The first magnetic field forming member and the second magnetic field forming member have a cylindrical shape with the same dimensions,
The central axes of the first magnetic field forming member and the second magnetic field forming member are above the central axis of the rotating shaft,
The distance between the radially innermost point of the magnetic flux concentrating groove in the radial direction of the rotary shaft and the center axis of the rotary shaft is equal to the outer diameter of the first magnetic field forming member and the second magnetic field forming member. ,
The glass plate polishing apparatus according to any one of claims 6 to 8. The magnetic flux concentration member increases the density of the magnetic flux in the space inside the magnetic flux concentration groove;
The glass plate polishing apparatus according to any one of claims 6 to 9.

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