TWI655995B - Method for manufacturing glass plate and grinding device for glass plate - Google Patents

Abstract

An object of the present invention is to provide a method for manufacturing a glass plate and a polishing device for a glass plate, which can improve the efficiency of polishing the end surface of a glass plate.

In the method for manufacturing a glass plate, the polishing slurry 24 held by the magnetic field formed by the first magnetic field forming member 22 and the second magnetic field forming member 23 is combined with the first magnetic field forming member 22 and the second magnetic field forming member 23 Rotating around the rotation axis 21, in this state, the end portion 92a of the glass plate 92 is brought into contact with the polishing slurry 24, and the end portion 92a is polished. The magnetic flux concentration member 25 concentrates the magnetic flux from the first magnetic field forming member 22 toward the second magnetic field forming member 23, thereby increasing the magnetic flux density. The magnetic flux concentration member 25 is a magnetic body attached to the first magnetic field forming member 22 and the second magnetic field forming member 23. The end portion 92 a of the glass plate 92 is brought into contact with the polishing slurry 24 held in the space where the magnetic flux density is increased by the magnetic flux concentration member 25.

Description

Method for manufacturing glass plate and grinding device for glass plate

The invention relates to a method for manufacturing a glass plate and a grinding device for a glass plate.

The glass sheet is cut to the required size during the manufacturing process. For example, the manufacturing processes of flat-panel display glass substrates such as liquid crystal displays and plasma displays, touch-control glass substrates, and protective glass substrates include the following steps: forming a scribe line on a large glass plate called mother glass, and Cut off. Microscopic cracks or very sharp edges usually form on the cut surface of the glass plate. In order to remove the edge formed on the cut surface, the cut surface is chamfered. For example, the cut surface is chamfered so that the cross section becomes an R shape. The chamfered cut surface is further finished into a mirror-like shape by grinding using a grinding wheel.

Patent Document 1 (International Publication No. 2012/067587) discloses a technique of using a magnetic fluid in an end surface polishing process of a glass plate. In the grinding process using magnetic fluid, the magnetic fluid containing abrasive particles is maintained between a pair of magnets, and the end face of the glass plate is brought into contact with the magnetic fluid. In this state, the end face of the glass plate and the magnetic fluid are relatively moved, thereby The end surface of the glass plate is ground. In the grinding process using a magnetic fluid, the magnetic fluid is subjected to the grinding process following the shape of the workpiece, so the damage to the workpiece is relatively small. Therefore, when a grinding wheel holding a magnetic fluid is used in the grinding process of the end face of the glass plate, a smoother end face can be obtained compared to the grinding process using a grinding wheel containing diamond abrasive grains.

[Prior technical literature] [Patent Literature]

[Patent Document 1] International Publication No. 2012/067587

However, in the previous grinding wheel that held the magnetic fluid, the density of the magnetic flux existing in the space around the pair of magnets was low, and the holding force of the magnetic fluid was insufficient. Therefore, the conventional grinding wheel has the following problems: the grinding efficiency of the end surface of the glass plate is low, and it takes a very long time to obtain the end surface of the required quality. Therefore, it is required to increase the density of the magnetic flux existing in the space around the magnet in one of the grinding wheels and increase the holding force of the magnetic fluid to improve the grinding efficiency of the glass plate.

An object of the present invention is to provide a method for manufacturing a glass plate and a polishing device for a glass plate, which can improve the efficiency of polishing the end surface of a glass plate.

In the manufacturing method of the glass plate of the present invention, the magnetic abrasive grains held by the magnetic field formed by the first magnetic field forming member and the second magnetic field forming member are rotated together with the first magnetic field forming member and the second magnetic field forming member. The shaft is rotated, and the end portion of the glass plate is brought into contact with the magnetic abrasive grains in this state, thereby polishing the end portion. In this glass plate manufacturing method, a magnetic flux concentration member is used to concentrate the magnetic flux from the first magnetic field forming member toward 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. The manufacturing method of the glass plate is such that the end portion of the glass plate is brought into contact with magnetic abrasive grains held in a space where the magnetic flux density is increased by a magnetic flux concentration member.

The manufacturing method of this glass plate is a method which grinds by making the end surface of a glass plate contact the magnetic abrasive grain which rotates about a rotation axis. The magnetic abrasive particles 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 configured to increase the density of the magnetic flux by concentrating the magnetic flux in at least a part of the space holding the magnetic abrasive particles. In a space where the magnetic flux density is increased by using a magnetic flux concentration member, the first magnetic field shape The holding force of the magnetic abrasive particles of the forming member and the second magnetic field forming member is larger than the holding force in other spaces. The higher the holding force of the magnetic abrasive particles, the harder it is for the magnetic abrasive particles to move when the end face of the glass plate has been in contact with the magnetic abrasive particles. Thereby, the grinding pressure applied to the end face of the glass plate by the rotating magnetic abrasive particles becomes high, and the end face grinding ability of the glass plate also becomes high. Therefore, the manufacturing method of the glass plate can improve the polishing efficiency of the end surface of the glass plate.

The method of manufacturing the glass plate is preferably a space between the first magnetic field forming member and the second magnetic field forming member, and the first magnetic field forming member and the second magnetic field forming member, radially outward of the rotation axis. In at least one of the spaces, the magnetic flux density increases due to the magnetic flux concentration member.

In the manufacturing method of the glass plate, a magnetic flux concentrating member is provided so that the magnetic flux lines pass through the magnetic flux concentrating members, the magnetic flux lines go from the first magnetic field forming member toward the second magnetic field forming member, and the space held by the magnetic abrasive particles . As a result, the density of the magnetic flux increases in the space held by the magnetic abrasive particles in contact with the end face of the glass plate. Therefore, the manufacturing method of the glass plate can improve the polishing efficiency of the end surface of the glass plate.

Moreover, it is preferable that the manufacturing method of the glass plate is such that a space on the opposite side of the second magnetic field forming member from the side on which the first magnetic field forming member is located and where the first magnetic field forming member is located on the second magnetic field forming member In at least one of the spaces on the opposite side, the density of the magnetic flux is increased by the magnetic flux concentration member.

In the manufacturing method of the glass plate, a magnetic flux concentrating member is provided so that the magnetic flux lines pass through the magnetic flux concentrating members, the magnetic flux lines go from the first magnetic field forming member toward the second magnetic field forming member, and the space held by the magnetic abrasive particles . As a result, the density of the magnetic flux increases in the space held by the magnetic abrasive particles in contact with the end face of the glass plate. Therefore, the manufacturing method of the glass plate can improve the polishing efficiency of the end surface of the glass plate.

A polishing device 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 particles, and a magnetic flux concentration member. First magnetic field forming member Knot on the rotation axis and rotate around the rotation axis. The second magnetic field forming member is connected to the rotation axis and rotates around the rotation axis. The magnetic abrasive particles 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. The magnetic flux concentration member concentrates the magnetic flux from the first magnetic field forming member toward the second magnetic field forming member, thereby increasing the density of the magnetic flux. The magnetic abrasive grains held by the space where the magnetic flux concentration member is used to increase the magnetic flux density are rotated together with the first magnetic field forming member and the second magnetic field forming member about a rotation axis, and in this state are in contact with the ends of the glass plate While grinding the ends.

The polishing device for the glass plate is preferably a space between the first magnetic field forming member and the second magnetic field forming member, and a rotation axis of the first magnetic field forming member and the second magnetic field forming member. The magnetic flux density is increased in at least one of the radially outer spaces.

In the polishing device for the glass plate, it is preferable that the magnetic flux concentration member is installed at least on the radially outer side of the rotation axis of the first magnetic field formation member and the second magnetic field formation member, and has a magnetic flux concentration groove. The magnetic flux concentration groove is a groove whose surface on the radially outer side of the rotation axis of the magnetic flux concentration member is at a right angle to the center axis of the rotation axis.

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

In the polishing device for the glass plate, it is preferable that the magnetic flux concentrating member is further mounted on each of the first magnetic field forming member and the second magnetic field forming member in a center axis direction of the rotation axis.

In the polishing device of the glass plate, a magnetic flux concentration member is provided so that the magnetic flux lines pass through the magnetic flux concentration members. The magnetic flux lines pass from the first magnetic field forming member toward the second magnetic field forming member and pass through the magnetic flux concentration groove. Thereby, the density of the magnetic flux in the magnetic flux concentration groove is increased. Therefore, the glass plate manufacturing device can improve the grinding efficiency of the end surface of the glass plate. The magnetic flux concentration member may be provided between the first magnetic field forming member and the second magnetic field forming member.

In the polishing device for the glass plate, it is preferable that the first magnetic field forming member is adjacent to the second magnetic field forming member in a central axis direction of the rotation axis.

In the polishing device for the glass plate, the first magnetic field forming member and the second magnetic field forming member preferably have a cylindrical shape having the same size. The center axes of the first magnetic field forming member and the second magnetic field forming member are preferably located on the center axis of the rotation axis. The distance between the magnetic flux concentration groove located at the innermost point in the radial direction of the rotation axis and the center axis of the rotation axis is preferably equal to the outer diameters of the first magnetic field forming member and the second magnetic field forming member.

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

In the polishing device for the glass plate, it is preferable that the magnetic flux concentration member increases the density of the magnetic flux in the space inside the magnetic flux concentration groove.

The glass plate manufacturing method and the glass plate grinding device of the present invention can improve the end surface grinding efficiency of the glass plate.

10‧‧‧ Grinding device

12‧‧‧ transfer agency

14‧‧‧ Grinding mechanism

20‧‧‧ grinding wheel

21‧‧‧rotation axis

21a‧‧‧center axis of rotation axis

22‧‧‧ the first magnetic field forming member

22a‧‧‧The first center member

22b‧‧‧The first ring magnet

22c‧‧‧The first upper magnetic field forming surface

22d‧‧‧The first lower magnetic field forming surface

23‧‧‧Second magnetic field forming member

23a‧‧‧ 2nd central member

23b‧‧‧2nd ring magnet

23c‧‧‧The second upper magnetic field forming surface

23d‧‧‧The second lower magnetic field forming surface

24‧‧‧Grinding slurry (magnetic abrasive particles)

24a‧‧‧Slurry surface

25‧‧‧ magnetic flux concentration component

25a‧‧‧ Upper Concentrated Member

25b‧‧‧ Lower central component

25c‧‧‧ 1st side concentrated member

25d‧‧‧ 2nd side concentrated member

25e‧‧‧Side 1

25f‧‧‧The first slope

25g‧‧‧The second side

25h‧‧‧2nd inclined surface

26‧‧‧ magnetic flux concentration groove

27‧‧‧ magnetic flux concentration space

90‧‧‧ molten glass

91‧‧‧glass ribbon

92‧‧‧ glass plate

92a‧‧‧End of glass plate (end of glass plate)

100‧‧‧ glass plate manufacturing equipment

101‧‧‧ melting device

102‧‧‧clarification device

103‧‧‧mixing device

104‧‧‧forming device

105‧‧‧ cutting device

120‧‧‧ grinding wheel

121‧‧‧rotation axis

122‧‧‧ the first magnetic field forming member

122a‧‧‧The first center member

122b‧‧‧The first ring magnet

123‧‧‧Second magnetic field forming member

123a‧‧‧The second center member

123b‧‧‧ 2nd ring magnet

124‧‧‧ ground slurry

125‧‧‧ spacer

126‧‧‧ Magnetic field forming groove

127‧‧‧Slot space

220‧‧‧ grinding wheel

221‧‧‧rotation axis

222‧‧‧The first magnetic field forming member

222a‧‧‧The first center member

222b‧‧‧The first ring magnet

223‧‧‧Second magnetic field forming member

223a‧‧‧ 2nd central member

223b‧‧‧ 2nd ring magnet

224‧‧‧Grinding slurry

226‧‧‧ Magnetic field forming groove

227‧‧‧Slot space

320‧‧‧ grinding wheel

321‧‧‧rotation axis

322‧‧‧ the first magnetic field forming member

322a‧‧‧The first center member

322b‧‧‧The first ring magnet

323‧‧‧Second magnetic field forming member

323a‧‧‧ 2nd central member

323b‧‧‧2nd ring magnet

324‧‧‧Grinding slurry

325‧‧‧magnetic flux concentration member

325c‧‧‧The first side concentrated member

325d‧‧‧ 2nd side concentrated member

326‧‧‧ magnetic field forming groove

327‧‧‧ magnetic flux concentration space

420‧‧‧Grinding wheel

421‧‧‧rotation axis

422‧‧‧The first magnetic field forming member

422a‧‧‧The first center member

422b‧‧‧The first ring magnet

423‧‧‧Second magnetic field forming member

423a‧‧‧2nd central component

423b‧‧‧2nd ring magnet

424‧‧‧Grinding slurry

425‧‧‧ magnetic flux concentration component

425a‧‧‧upper central component

425b‧‧‧Lower central component

425c‧‧‧The first side concentrated member

425d‧‧‧ 2nd side concentrated member

425e‧‧‧Intermediate member

425f‧‧‧1st side

425g‧‧‧1st inclined surface

425h‧‧‧Side 2

425i‧‧‧ 2nd inclined surface

426‧‧‧ magnetic flux concentration groove

427‧‧‧ magnetic flux concentration space

520‧‧‧Grinding wheel

521‧‧‧rotation axis

522‧‧‧The first magnetic field forming member

522a‧‧‧The first center member

522b‧‧‧The first ring magnet

523‧‧‧Second magnetic field forming member

523a‧‧‧ 2nd central member

523b‧‧‧2nd ring magnet

524‧‧‧Grinding slurry

525‧‧‧ magnetic flux concentration component

525c‧‧‧The first side concentrated member

525d‧‧‧Second side concentrated member

525e‧‧‧Intermediate member

525f‧‧‧1st side

525g‧‧‧1st inclined surface

525h‧‧‧The second side

525i‧‧‧ 2nd inclined surface

526‧‧‧ magnetic flux concentration groove

527‧‧‧ magnetic flux concentration space

S10 ~ S80‧‧‧step

FIG. 1 is a flowchart of a method for manufacturing a glass plate according to this embodiment.

Fig. 2 is a schematic diagram of the device from the melting step to the cutting step in Fig. 1.

Fig. 3 is a schematic view of a polishing apparatus.

Figure 4 is an external view of a grinding wheel.

Fig. 5 is a sectional view of a grinding wheel.

Fig. 6 is a part of a sectional view of a grinding wheel.

Fig. 7 is a diagram showing a magnetic field formed by a grinding wheel.

Fig. 8 is a sectional view of a grinding wheel as a first comparative example.

FIG. 9 is a diagram showing a magnetic field generated by a grinding wheel as a first comparative example.

Fig. 10 is a cross-sectional view of a polishing wheel as a second comparative example.

FIG. 11 is a diagram showing a magnetic field generated by a grinding wheel as a second comparative example.

FIG. 12 is a sectional view of a grinding wheel according to a modified example A. FIG.

FIG. 13 is a diagram showing a magnetic field generated by a grinding wheel of a modified example A. FIG.

FIG. 14 is a sectional view of a grinding wheel according to a modified example B. FIG.

FIG. 15 is a part of a cross-sectional view of a grinding wheel according to Modification B. FIG.

FIG. 16 is a diagram showing a magnetic field generated by a grinding wheel according to a modification B. FIG.

FIG. 17 is a sectional view of a grinding wheel according to a modification C. FIG.

FIG. 18 is a part of a cross-sectional view of a grinding wheel of Modification C. FIG.

FIG. 19 is a diagram showing a magnetic field generated by a grinding wheel of Modification C. FIG.

FIG. 20 is a sectional view of a grinding wheel according to a modification D. FIG.

FIG. 21 is a part of a sectional view of a grinding wheel according to a modification E. FIG.

FIG. 22 is a part of a cross-sectional view of a grinding wheel of Modification F. FIG.

FIG. 23 is a part of a sectional view of a grinding wheel according to a modification G. FIG.

A method for manufacturing a glass plate as an embodiment of the present invention will be described with reference to the drawings. The manufacturing method of the glass plate of this embodiment includes the method of grinding the end surface of the glass plate manufactured using the overflow down-draw method.

(1) Outline of manufacturing method of glass plate

First, the outline of the manufacturing method of a glass plate is demonstrated. The glass plate manufactured by this manufacturing method is used as a glass substrate for a flat panel display (FPD) such as a liquid crystal display, a plasma display, and an organic EL display, a touch glass substrate, a glass substrate for a solar cell panel, and a protective glass substrate. . 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% to 70% by mass, (b) Al ₂ O ₃ : 10% to 25% by mass, (c) B ₂ O ₃ : 5% to 18% by mass, (d) MgO : 0% to 10% by mass, (e) CaO: 0% to 20% by mass, (f) SrO: 0% to 20% by mass, (g) BaO: 0% to 10% by mass, (h ) RO: 5 mass% to 20 mass% (R is at least one selected from Mg, Ca, Sr, and Ba), (i) R ' ₂ O: 0 mass% to 2.0 mass% (R' is from Li (Na, K and at least one selected), (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 an overflow down-draw method is demonstrated. FIG. 1 is an example of a flowchart showing a manufacturing process of a glass plate. The glass plate manufacturing process mainly includes a melting step (step S10), a clarification step (step S20), a stirring step (step S30), a forming step (step S40), a slow cooling step (step S50), and a cutting step (step S60). , A grinding step (step S70), and a polishing step (step S80). FIG. 2 is a schematic diagram of the glass plate manufacturing apparatus 100 from the melting step S10 to the cutting step S60. The glass plate manufacturing apparatus 100 includes a melting apparatus 101, a clarifying 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 a melting device 101 using a heating device such as a burner, and a molten glass 90 having a high temperature of 1500 ° C to 1600 ° C is generated. The glass raw material is prepared in such a manner that a glass having a desired composition can be substantially obtained. Here, "substantially" means that the presence of other trace components is allowed in a range of less than 0.1% by mass.

In the clarification step S20, the clarification device 102 is used to further increase the temperature of the molten glass 90 generated in the melting step S10, thereby clarifying the molten glass 90. In the clarification device 102, the temperature of the molten glass 90 is raised to 1600 ° C to 1750 ° C, preferably to 1650 ° C to 1700 ° C. In the clarification device 102, the micro-bubbles of O ₂ , CO ₂ and SO ₂ contained in the molten glass 90 grow due to O ₂ generated by reduction of clarifying agents such as SnO ₂ contained in the glass raw material, and the liquid of the molten glass 90 floats on Disappeared.

In the stirring step S30, the molten glass 90 that has been clarified in the clarification step S20 is stirred by the stirring device 103 to achieve chemical homogenization and thermal homogenization. In the stirring device 103, the molten glass 90 is stirred while rotating around the axis while flowing in the vertical direction, and is sent to the downstream process from the outflow port provided at the bottom of the stirring device 103. In the stirring step S30, glass components such as zirconia-rich molten glass 90 and the like having a specific gravity different from the average specific gravity of the molten glass 90 are removed from the stirring device 103.

In the forming step S40, the glass ribbon 91 is formed from the molten glass 90 that has been stirred in the stirring step S30 by the forming apparatus 104 using the overflow down-draw method. Specifically, the molten glass 90 overflowing and shunting from the upper part of the forming unit flows downward along the side wall of the forming unit and merges at the lower end of the forming unit, thereby continuously forming the glass ribbon 91. Before flowing into the forming step S40, the molten glass 90 is cooled to a temperature suitable for forming by the overflow down-draw method, for example, 1200 ° C.

In the slow cooling step S50, the temperature of the glass ribbon 91 continuously generated in the forming step S40 by the forming device 104 is controlled so as not to cause strain and warping, and the temperature is gradually cooled to below the slow cooling point.

In the cutting step S60, the glass ribbon 91, which is gradually cooled to room temperature in the slow cooling step S50, is cut by the cutting device 105 every predetermined length. When the glass ribbon 91 is switched, a score line is formed on the glass ribbon 91 so that the tensile stress is concentrated on the score line and the glass ribbon 91 is cut. To form the score line, a method using a diamond cutter to mechanically form it, and a method using laser heating and rapid cooling to advance the initial crack are generally used. In the cutting process S60, the glass ribbon 91 cut | disconnected every predetermined length is further cut | disconnected to specific size, and the glass plate 92 is obtained.

In the grinding step S70, the corners of the glass plate 92 obtained in the cutting step S60 are ground, and the end faces of the glass plate 92 are chamfered. In the corner between the end surface and the main surface of the glass plate 92 cut in the cutting step S60, a very sharp edge is formed. In the grinding step S70, a corner portion of the glass plate 92 is ground using a diamond wheel or the like, thereby removing the edge formed at the corner portion. 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 specific range. The processing width is the maximum value of the distance between the outermost end of the chamfered end face of the glass plate 92 and the boundary between the end face and the main surface. During the chamfering process, the force endured by the end face of the glass plate 92 from the diamond wheel or the like will gradually decrease from the outermost end of the end face toward the boundary between the end face and the main surface. Therefore, when the processing width is too large, the area near the boundary between the end surface of the glass plate 92 and the main surface may be insufficiently 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 be insufficiently removed. When the thickness of the glass plate 92 is set to t, the above-mentioned specific range of the processing width is preferably 1 / 50t to t, more preferably 1 / 20t to 1 / 2t, and further preferably 1 / 10t to 1 / 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 surface of the chamfered glass plate 92 in the grinding step S70, a layer including microcracks called microcracks or horizontal cracks is formed. This layer is called the process metamorphic layer or the fragile failure layer. When the processed deterioration layer is formed, the breaking strength of the end face of the glass plate 92 is reduced. In the grinding step S70, the end face of the glass plate 92 is ground so that the thickness of the processed metamorphic layer is less than 3 μm.

More specifically, the grinding process S70 includes a first grinding process and a second grinding process. In the first grinding step, a grinding wheel (metal bonding diamond wheel, etc.) reinforced with a metal bonding agent is used. In the second grinding step, a grinding wheel (resin-bonded diamond wheel, etc.) reinforced with a resin binder is used. In the second grinding step, a grinding wheel having a lower hardness and rigidity than the grinding wheel used in the first grinding step is used. In the first grinding step, an R shape required for the end surface of the glass plate 92 is formed in a short time. In the second grinding step, processing is performed in a short time so that the shape of the end surface of the glass plate 92 is uniform and the surface roughness of the end surface is reduced.

In the grinding step S80, the end face of the chamfered glass plate 92 in the grinding step S70 Grind. The purpose of the polishing step S80 is to further remove the processing-deteriorated layer and improve the breaking strength of the end surface of the glass plate 92.

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

(2) Details of the grinding process

Next, the polishing process of the end surface 92a of the glass plate 92 performed in the polishing process S80 is demonstrated. In the polishing step S80, the end surface 92 a of the glass plate 92 is polished by the polishing device 10. FIG. 3 is a schematic view of the polishing apparatus 10. The polishing device 10 grinds the end surface 92 a while conveying the glass plate 92 while facing one of the long sides of 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 conveyance mechanism 12 conveys the glass plate 92 along the long side of the glass plate 92. The conveyance mechanism 12 conveys the glass plate 92 using a conveyor belt, a vacuum float plate, or the like. The vacuum floating plate is a device that blows air toward the lower surface of the glass plate 92 and sucks air from the space below the glass plate 92 to suspend the glass plate 92 stably. The polishing mechanism 14 is disposed on both sides of the glass plate 92 so as to face the one end surface 92 a of the glass plate 92 respectively. The polishing mechanism 14 includes a polishing wheel 20. The polishing mechanism 14 presses the grinding wheel 20 in rotation 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 conveyance direction of the glass plate 92 and the rotation direction of the grinding wheel 20 are indicated by arrows.

(2-1) Structure of grinding wheel

Next, the structure of the grinding wheel 20 is demonstrated. In the following description, the "conveying direction" refers to the long-side direction of the glass plate 92, that is, the longitudinal direction of the end surface 92a of the glass plate 92, and the direction in which the glass plate 92 is conveyed by the conveyance mechanism 12. The "width direction" refers to a direction along the surface of the glass plate 92, and refers to a direction orthogonal to the conveyance direction. The “vertical direction” refers to a direction orthogonal to the surface of the glass plate 92. In the drawing, the conveying direction is indicated by the "y-axis", the width direction is indicated by the "x-axis", and the vertical direction is indicated by the "z-axis". Will be orthogonal to the vertical direction The plane is called the "horizontal plane". The surface of the glass plate 92 is parallel to the horizontal plane.

The polishing wheel 20 is used to polish the end surface 92 a of the glass plate 92. FIG. 4 is an external view of the grinding wheel 20. FIG. 5 is a cross-sectional view of the grinding wheel 20 after the grinding wheel 20 is cut along the xz plane including the central axis 21 a of the rotation axis 21. In FIG. 5, for reference, the end of the glass plate 92 to be ground by the grinding wheel 20 is shown. As shown in FIG. 5, the end surface 92 a of the glass plate 92 is chamfered into an R shape. The polishing wheel 20 mainly includes a rotation 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) Rotary shaft

The rotation shaft 21 is a shaft for rotating the grinding wheel 20. The grinding wheel 20 rotates about the central axis 21 a of the rotation axis 21. The central axis 21a is parallel to the vertical direction. As shown in FIG. 3, the rotation direction of the grinding wheel 20 is a direction which moves the glass plate 92 in the direction opposite to the conveyance direction of the glass plate 92. The rotating shaft 21 is formed by using a non-magnetic stainless steel material such as SUS304 so that the magnetic flux is not concentrated on the rotating shaft 21. Hereinafter, the diameter direction of the rotating shaft 21, that is, the direction orthogonal to the central axis 21a of the rotating shaft 21 is referred to as "radial direction". Regarding the two points on the radial straight line, the side on which one point is longer from the central axis 21a is referred to as "radial outer side", and the side on which one point is shorter from the central axis 21a is referred to as "radial outer side". "Radial inside".

The rotating shaft 21 is connected to a rotating shaft driving unit (not shown) and rotates around the central shaft 21a at a required rotation speed. The rotating shaft 21 is connected to a rotating shaft moving mechanism (not shown), and moves so as to approach or depart 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 center member 22 a and a first ring-shaped magnet 22 b. The first center member 22a is a cylindrical member having a through hole formed in the vertical direction. The first center member 22a is formed from a non-magnetic stainless steel material such as SUS304 so that the magnetic flux is not concentrated on the first center member 22a. The rotation shaft 21 penetrates a through hole of the first center member 22a. The first center member 22 a is fixed to the rotation shaft 21. The first annular magnet 22b is a cylindrical member having a through hole formed in the vertical direction. First center member 22a The through hole is fitted in the first annular magnet 22b. The first ring-shaped magnet 22b is a magnet such as a permanent magnet and an electromagnet, and is magnetized in the vertical direction. The upper side is the N pole and the lower side is the S pole. Hereinafter, the upper surface of the first annular magnet 22b is referred to as a first upper magnetic field formation surface 22c, and the lower surface of the first annular magnet 22b is referred to as a first lower magnetic field formation surface 22d.

(2-1-3) The second magnetic field forming member

As shown in FIG. 5, the second magnetic field forming member 23 includes a second center member 23 a and a second ring-shaped magnet 23 b. The second center member 23a is a cylindrical member having a through hole formed in the vertical direction. The second center member 23a is formed by using a non-magnetic stainless steel material such as SUS304 so that the magnetic flux is not concentrated on the second center member 23a. The rotation shaft 21 penetrates a through hole of the second center member 23a. The second center member 23 a is fixed to the rotation shaft 21. The second annular magnet 23b is a cylindrical member having a through hole formed in the vertical direction. The second center member 23a is fitted into the through hole of the second ring-shaped magnet 23b. The second ring-shaped magnet 23b is a magnet such as a permanent magnet and an electromagnet, and is magnetized in the vertical direction. The upper side is the N pole and the lower side is the S pole. Hereinafter, the upper surface of the second annular magnet 23b is referred to as a second upper magnetic field formation surface 23c, and the lower surface of the second annular magnet 23b is referred to as a second lower magnetic field formation surface 23d.

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

The first magnetic field forming member 22 and the second magnetic field forming member 23 form a magnetic field in a space around them. Thereby, the grinding wheel 20 can form a magnetic field in the space around it. In addition, the first ring-shaped magnet 22b of the first magnetic field forming member 22 and the second ring-shaped magnet 23b of the second magnetic field forming member 23 may be magnets having S poles on the upper side and N poles on the lower side.

(2-1-4) grinding slurry

The polishing slurry 24 is a mixture of magnetic abrasive particles and a liquid. The polishing slurry 24 is held by a magnetic field formed by the polishing wheel 20.

The magnetic abrasive grains are abrasive grains used for grinding a brittle material such as a glass plate 92. The magnetic abrasive particles include, for example, magnetic particles such as iron oxide and ferrite. When ferrite is used as the magnetic abrasive particles, the amount of additives used to prevent oxidation or the amount of additives used to prevent oxidation is not required to be reduced. Therefore, the deterioration of the magnetic abrasive particles with time can be suppressed.

The liquid mixed with the magnetic abrasive particles is, for example, water, hydrocarbons, esters, ethers, and hydrogen fluoride. The liquid mixed with the magnetic abrasive particles 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 particles is preferably water. By using water, an increase in the temperature of the polishing slurry 24 of the glass plate 92 during the polishing process can be suppressed.

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

As the magnetic abrasive grains of the polishing slurry 24, for example, a 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 tackifier, and water in the magnetic abrasive particles. In addition, a non-magnetic slurry such as cerium oxide, aluminum oxide, and silicon oxide may be further mixed with the polishing slurry 24 to increase the polishing power.

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

(2-1-5) Magnetic flux concentration member

As shown in FIG. 5, the magnetic flux concentration member 25 includes an upper concentration member 25 a, a lower concentration member 25 b, a first side concentration member 25 c, and a second side concentration member 25 d. Each member constituting the magnetic flux concentration member 25 is formed of soft iron steel made of ferromagnetic material such as SUS430. In addition, each member constituting the magnetic flux concentration member 25 may have high rigidity, and use the strength of other materials. Magnetic body molding. When the liquid mixed with the magnetic abrasive particles of the polishing slurry 24 is water, the magnetic flux concentration member 25 is preferably formed from a material that is not easily rusted, such as stainless steel. The first magnetic field forming member 22 and the second magnetic field forming member 23 are covered by a magnetic flux concentration member 25 except for a portion where the rotation shaft 21 projects 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 in which the rotation shaft 21 penetrates in the vertical direction. The magnetic flux concentration member 25 is fixed to the rotation shaft 21. FIG. 6 is an enlarged view of the radially outer end of the cross-sectional view of the grinding wheel 20 shown in FIG. 5. In FIG. 6, the polishing slurry 24 and the glass plate 92 are omitted.

The upper concentrating member 25a is provided so as to cover at least the upper surface (N pole) of the first ring-shaped magnet 22b. The lower concentrating member 25b is provided so as to cover at least the lower surface (S-pole) of the second ring-shaped magnet 23b. The first side concentrated member 25 c covers the outer peripheral surface of the first magnetic field forming member 22. The second side concentrated 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 concentrated member 25 a, the lower concentrated member 25 b, the first side concentrated member 25 c, and the second side concentrated member 25 d are all located at the same position in the radial direction. As shown in FIG. 6, the upper surface of the first side concentrated member 25c is in contact with the radially outer lower surface of the upper concentrated member 25a, and the lower surface of the second side concentrated member 25d and the radially outer lower surface of the lower concentrated member 25b are in contact with each other. The upper surface is in contact.

As shown in FIG. 6, the first side concentrated member 25 c includes a first side surface 25 e and a first inclined surface 25 f. The first side surface 25e is the outer peripheral surface of the first side concentrated member 25c. The first inclined surface 25f is a plane 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 radially innermost side of the first inclined surface 25f 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 concentrated member 25 d has a second side surface 25 g and a second inclined surface 25 h. The second side surface 25g is an outer peripheral surface of the second side portion concentrating member 25d. The second inclined surface 25h is a plane 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 radially innermost side of the second inclined surface 25h and the upper end of the outer peripheral surface of the second magnetic field forming member 23 Consistent.

The first magnetic field forming member 22 is adjacent to the second magnetic field forming member 23 in the vertical direction. Therefore, the point radially inward of the first inclined surface 25f of the first side concentrated member 25c coincides with the point radially inward of the second inclined surface 25h of the second side concentrated member 25d. As a result, as shown in FIG. 6, a magnetic flux concentration groove 26 is formed on the outer peripheral surface of the magnetic flux concentration member 25. The magnetic flux concentration groove 26 is a V-shaped groove including a first inclined surface 25f and a second inclined surface 25h. The space inside the magnetic flux concentration groove 26, that is, the space between the first inclined surface 25f and the second inclined surface 25h is a magnetic flux concentration space 27. The magnetic flux concentration space 27 is a space where the magnetic flux formed by the grinding wheel 20 is the magnetic flux concentration. A magnetic flux concentrating member 25 containing a ferromagnetic body that is easy to pass through the magnetic field is used to direct the magnetic field in a desired direction, thereby serving as a magnetic circuit of a closed loop that is a ghost line representing the magnetic field, that is, a magnetic field line. The magnetic flux concentration space 27 is a space containing a part of the magnetic circuit.

The most radially inward point of the magnetic flux concentration space 27 coincides with the most radially outward point 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 a magnetic field formed by the polishing wheel 20.

In addition, each member constituting the magnetic flux concentration member 25 may be integrally formed. For example, the upper concentrated member 25a and the first side concentrated member 25c may be formed as an integrated member, and the lower concentrated member 25b and the second side concentrated member 25d may be formed as an integrated member.

(2-2) Magnetic field formed by the grinding wheel

FIG. 7 is an enlarged view of the radially outer end of the cross-sectional view of the grinding wheel 20 shown in FIG. 5. In FIG. 7, magnetic field lines are described as false image lines representing 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 addition, in FIG. 7, in order to make the magnetic field lines stand out, the hatched lines shown in FIGS. 5 and 6 are omitted.

In FIG. 7, magnetic lines of force from the N pole of the first ring-shaped magnet 22 b of the first magnetic field forming member 22 toward the S pole of the second ring-shaped magnet 23 b of the second magnetic field forming member 23 are shown. In FIG. 7, magnetic field lines are shown, for example, from the first upper portion of the first magnetic field forming member 22. The magnetic field formation surface 22 c departs from the radially outer space of the first magnetic field formation member 22 and the second magnetic field formation member 23 and reaches the second lower magnetic field formation surface 23 d of the second magnetic field formation member 23.

The magnetic flux concentration member 25 increases the magnetic flux density of the magnetic flux concentration space 27 held by the polishing slurry 24. Specifically, the upper concentrated member 25a guides the magnetic force lines so as to form magnetic lines of force that flow out (release) from the first upper magnetic field forming surface 22c and pass through the magnetic path of the upper concentrated member 25a radially outward. The upper concentrating member 25a suppresses the leakage of magnetic lines of force flowing upward from the first upper magnetic field forming surface 22c to the space above the upper concentrating member 25a. The first side concentrated member 25c guides the magnetic force lines such that the magnetic lines of force guided by the upper concentrated member 25a pass through the first side concentrated members 25c and face the magnetic flux concentration space 27. The first side concentrated member 25c prevents the magnetic lines of force guided by the upper concentrated member 25a from leaking out to a space radially outside the first side concentrated member 25c. The second side concentrated member 25d guides the magnetic lines of force so that the magnetic lines of force guided by the first side concentrated members 25c pass through the second side concentrated members 25d and face the lower concentrated member 25b. The second side concentrated member 25d suppresses leakage of magnetic lines of force guided by the first side concentrated member 25c to a space radially outside the second side concentrated member 25d. The lower concentrated member 25b guides the magnetic lines of force so that the magnetic lines of force guided by the second side concentrated member 25d pass through the magnetic path of the lower concentrated member 25b radially inward. The lower concentrated member 25b suppresses the magnetic lines of force guided by the second side concentrated member 25d from leaking to the space below the lower concentrated member 25b.

Therefore, as shown in FIG. 7, the magnetic flux concentration member 25 can guide a part of the magnetic field lines flowing upward from the first upper magnetic field formation surface 22 c to the second lower magnetic field formation without leaking to the space around the grinding wheel 20. Face 23d. Thereby, a magnetic circuit with less leakage magnetic flux can be formed. Comparing the case where the magnetic flux concentration member 25 is provided and the magnetic flux lines flow out to the magnetic flux concentration member 25 and the case where the magnetic flux concentration member 25 is not provided and the magnetic flux lines flow to the surrounding space, the former allows the magnetic field to pass through the included magnetic field (magnetic field lines). The magnetic flux concentration member 25 of the magnetic body reduces the amount of magnetic flux leaking into the space, and forms a magnetic circuit with a strong magnetomotive force. On the other hand, the latter will Since the magnetic field is leaked to the surrounding space, compared with the former, a magnetic circuit with weak magnetomotive force is formed. Therefore, starting from the first upper magnetic field formation surface 22c, the leakage magnetic flux in the magnetic circuit indicated by the magnetic field lines passing through the magnetic flux concentration member 25 as a ferromagnetic body and reaching the second lower magnetic field formation surface 23d is small. Therefore, the difference between the magnetic force indicated by the magnetic force lines flowing upward from the first upper magnetic field formation surface 22c and the magnetic force indicated by the magnetic force lines passing through the magnetic flux concentration space 27 is small. Therefore, by attaching the magnetic flux concentrating member 25 to the first magnetic field forming member 22 and the second magnetic field forming member 23, the magnetic flux concentrating space 27 is provided to surround the first magnetic field forming member 22 and the second magnetic field forming member 23. The effect of increasing the magnetic flux density in space.

The polishing slurry 24 is held by the magnetic field of 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 by 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 which fills the magnetic flux concentration groove 26. The higher the magnetic flux density of the magnetic flux concentration space 27, the higher the intensity of the magnetic field of the magnetic flux concentration space 27. Therefore, the magnetic abrasive particles contained in the polishing slurry 24 are subjected to the force of the magnetic field from the magnetic flux concentration space 27. The size becomes higher. In other words, the magnetic field holding force of the polishing slurry 24 formed by the first magnetic field forming member 22 and the second magnetic field forming member 23 in the magnetic flux concentration space 27 is increased by the magnetic flux concentration member 25. Therefore, the magnetic flux concentration member 25 can increase the holding force of the polishing wheel 20 on the polishing slurry 24.

(2-3) Operation of the grinding device

In the polishing step S80, a step of polishing the end surface 92a of the glass plate 92 by the polishing device 10 will be described. First, the glass plate 92 whose edges are chamfered into an R shape is transported by the transport mechanism 12. The glass plate 92 conveyed in the conveyance direction gradually approaches the grinding wheel 20 of the grinding mechanism 14. The grinding mechanism 14 may be provided in advance so that the position of the pair of grinding wheels 20 matches the width of the glass plate 92. In addition, the grinding mechanism 14 may also use a sensor or the like to detect that the end surface 92a of the glass plate 92 is very close to the grinding wheel 20, or that the end surface 92a of the glass plate 92 has contacted the grinding wheel 20, and then set the center axis of the rotation axis 21 The grinding wheel 20 which rotates around 21a is moved toward the end surface 92a of the glass plate 92. As a result, as shown in FIG. 5, the end surface 92 a of the glass plate 92 is from the slurry surface. 24a is inserted into the polishing slurry 24. 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. With this, in a state where the end surface 92a of the glass plate 92 is in contact with the polishing slurry 24, the rotating grinding wheel 20 and the end surface 92a of the glass plate 92 are relatively moved in the conveying direction. The end surface 92a of the glass plate 92 collides with the magnetic abrasive grains contained in the polishing slurry 24 which rotates with the grinding wheel 20, and grinds. Moreover, instead of moving the glass plate 92 in the conveying direction, the grinding wheel 20 may be moved in the conveying direction, and the rotating grinding wheel 20 and the end surface 92a of the glass plate 92 may be relatively moved in the conveying direction. Moreover, you may move both the glass plate 92 and the grinding wheel 20 in a conveyance direction, and may relatively move the grinding wheel 20 and the end surface 92a of the glass plate 92 in a conveyance direction in rotation.

A layer including microcracks called microcracks or horizontal cracks is formed on the end surface 92a of the glass plate 92 to be ground in the grinding step S70. This layer is called a process deterioration layer or a fragile damage layer, and has a thickness of less than 3 μm. In the grinding step S70, the above-mentioned first grinding step and second grinding step are performed to control the quality of the end surface 92a of the glass plate 92. The grinding wheel 20 grinds the end surface 92a of the glass plate 92, and removes the processed deterioration layer or the fragile damage layer of the end surface 92a. The polishing wheel 20 preferably grinds the end surface 92a of the glass plate 92 such that the arithmetic average roughness Ra of the end surface 92a of the glass plate 92 becomes, for example, 10 nm or less.

(3) Features

The manufacturing method of the glass plate of this embodiment includes a polishing step S80. The polishing step S80 is performed by contacting the end surface 92a of the glass plate 92 manufactured by the overflow down-draw method with the rotating polishing slurry 24 and polishing. The polishing slurry 24 containing abrasive grains as magnetic abrasive grains is held at a magnetic flux formed on the outer peripheral surface of the magnetic flux concentration member 25 by a magnetic field formed by the first magnetic field forming member 22 and the second magnetic field forming member 23. The magnetic flux concentration space 27 inside the concentration groove 26. In the magnetic flux concentration space 27, the force of the magnetic field holding polishing slurry 24 formed by the first magnetic field formation member 22 and the second magnetic field formation member 23 is increased by the magnetic flux concentration member 25. The magnetic flux concentration member 25 suppresses magnetic lines of force flowing upward from the first upper magnetic field forming surface 22c of the first magnetic field forming member 22, and reaches the second lower magnetic field forming surface 23d of the second magnetic field forming member 23 Previously, it leaked into the space around the grinding wheel 20. That is, the magnetic flux concentrating member 25 constitutes a part of the magnetic circuit of the magnetic field lines flowing from the first upper magnetic field forming surface 22c to the second lower magnetic field forming surface 23d. The magnetic flux concentration member 25 guides the magnetic flux lines to the magnetic flux concentration space 27 to suppress a decrease in the magnetic flux density of the magnetic flux concentration space 27. Therefore, mounting the magnetic flux concentration member 25 on the first magnetic field formation member 22 and the second magnetic field formation member 23 has the effect of increasing the magnetic flux density of the magnetic flux concentration space 27.

As described above, the magnetic flux concentration space 27 is a space in which a decrease in magnetic flux density is suppressed by the magnetic flux concentration member 25. Therefore, the magnetic flux concentration space 27 is a space with a high holding force of the polishing slurry 24. The grinding wheel 20 holding the polishing slurry 24 and the end surface 92a of the glass plate 92 are relatively moved along the conveying direction. Therefore, the higher the holding force of the polishing slurry 24 is, the more polishing is performed when the end surface 92a contacts the polishing slurry 24. The more difficult it is to move the abrasive particles contained in the slurry 24. In addition, the more difficult it is to move the abrasive particles contained in the polishing slurry 24, the higher the pressure exerted by the abrasive particles on the end surface 92a, and therefore, the higher the grinding ability of the polishing wheel 20 to the end surface 92a of the glass plate 92. Therefore, the manufacturing method of the glass plate of this embodiment uses the magnetic flux concentration member 25 to increase the holding force of the polishing slurry 24 that grinds the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92 . In addition, the manufacturing method of the glass plate of this embodiment can locally increase the magnetic flux density of the magnetic flux concentration space 27. Therefore, even if the end surface 92a of the glass plate 92 is continuously processed, the polishing slurry 24 can be suppressed from the magnetic flux concentration groove. 26 outflow and dispersion.

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

In the first comparative example, the polishing wheel 120 mainly includes a rotation 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 different from the rotating shaft 21, the first magnetic field forming member 22, the second magnetic field forming member 23, and the polishing slurry 24 of this embodiment. The description is the same, so the description is omitted. The first magnetic field forming member 122 includes a first center member 122a and a first ring-shaped magnet 122b. The second magnetic field forming member 123 includes a second center member 123a and a second ring-shaped magnet 123b. The spacer 125 is a stainless steel plate, which is sandwiched between the first magnetic field forming member 122 and the second magnetic field forming member 123 and is penetrated by the rotation shaft 121. The spacer 125 has a cylindrical shape formed with a hole penetrated by the rotation shaft 121. The outer peripheral surface of the spacer 125 is located radially inward of 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 122b of the first magnetic field forming member 122 and the second annular magnet 123b of the second magnetic field forming member 123. The polishing slurry 124 is held in a groove space 127 inside the magnetic field forming groove 126.

As shown in FIG. 9, in the first comparative example, the magnetic field lines flowing upward from the upper surface of the first ring-shaped magnet 122 b pass through the space radially outward of the first magnetic field forming member 122 and the second magnetic field forming member 123. And reach the lower surface of the second ring-shaped magnet 123b. In the slot space 127, magnetic lines of force flowing upward from the upper surface of the second annular magnet 123b flow toward the lower surface of the first annular magnet 122b.

As shown in FIG. 9, in the first comparative example, the magnetic field lines flow out to a space on the opposite side of the slot space 127 via the first magnetic field forming member 122 and the second magnetic field forming member 123. Therefore, the magnetic flux leaked into the space on the opposite side becomes large, and therefore, the magnetic flux density of the slot space 127 is small. Therefore, the magnetic flux density of the slot space 127 is smaller than the magnetic flux density of the magnetic flux concentration space 27 of this embodiment.

In the second comparative example, the grinding wheel 220 mainly includes a rotating shaft 221 and a first magnetic field forming mechanism. The material 222, the second magnetic field forming member 223, and the polishing slurry 224. The rotation shaft 221 and the polishing slurry 224 are the same as the rotation shaft 21 and the polishing slurry 24 in this embodiment, respectively, and therefore description thereof is omitted. The first magnetic field forming member 222 includes a first center member 222a and a first ring-shaped magnet 222b. The second magnetic field forming member 223 includes a second center member 223a and a second ring-shaped magnet 223b. The first ring-shaped magnet 222b has an inclined surface inclined downward from the outer peripheral surface toward the inside in the radial direction and downward in the vertical direction. The second ring-shaped magnet 223b has an inclined surface that is inclined upward in the vertical direction from the outer peripheral surface toward the radially inner side. The inclined surfaces of the first annular magnet 222b and the second annular magnet 223b are the same as the first inclined surface 25f and the second inclined surface 25h of this embodiment, and a magnetic field forming groove 226 is formed as a V-shaped groove. . 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 which is a space inside the magnetic field forming groove 226.

As shown in FIG. 11, in the second comparative example, the magnetic field lines flowing upward from the upper surface of the first ring-shaped magnet 222 b pass through the space radially outward of the first magnetic field forming member 222 and the second magnetic field forming member 223. And reach the lower surface of the second ring-shaped magnet 223b. In the slot space 227, magnetic lines of force flowing upward from the upper surface of the second annular magnet 223b flow toward the lower surface of the first annular magnet 222b.

As shown in FIG. 11, in the second comparative example, the magnetic field lines flow out to a space on the opposite side of the slot space 227 via the first magnetic field forming member 222 and the second magnetic field forming member 223. Therefore, the magnetic flux leaking to the space on the opposite side becomes large, so the magnetic flux density of the slot space 227 is small. Therefore, the magnetic flux density of the slot space 227 is smaller than the magnetic flux density of the magnetic flux concentration space 27 of this embodiment.

According to the above description, compared with the grinding wheels 20 of this embodiment, the grinding wheels 120 and 220 of the first and second comparative examples that are not covered by a ferromagnetic body have a higher magnetic flux density in the space held by the grinding slurry 24. Low, the holding force of the polishing slurry 24 is small. In this embodiment, a magnetic flux concentration member 25 is provided in order to increase the magnetic flux density of at least a part of the magnetic flux concentration space 27 held by the polishing slurry 24. Therefore, the polishing apparatus 10 of this embodiment is used as The magnetic flux concentration member 25 of the ferromagnetic body increases the holding force of the polishing slurry 24 that polishes the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92.

(4) Variations

As mentioned above, although the manufacturing method of the glass plate of this embodiment was demonstrated, this invention is not limited to the said embodiment, Various improvement and change can be implemented in the range which does not deviate from the meaning of this invention.

(4-1) Modification A

As shown in FIG. 5, the magnetic flux concentration member 25 of this embodiment includes an upper concentration member 25 a, a lower concentration member 25 b, a first side concentration member 25 c, and a second side concentration member 25 d. 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 a grinding wheel 320 according to this modification. FIG. 13 is a part of a sectional view of the grinding wheel 320, and is a diagram showing a magnetic field formed by the grinding wheel 320. In FIG. 13, the polishing slurry 324 and the glass plate 92 are omitted. Note that in FIG. 13, hatching is omitted in order to make the magnetic field lines stand out.

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

As shown in FIG. 13, in this modification, a part of the magnetic field lines flowing upward from the upper surface of the first annular magnet 322 b passes through the first side concentrated member 325 c, the magnetic flux concentrated space 327, and the second side in this order. The part concentrating member 325d reaches the lower surface of the second ring-shaped magnet 323b. The magnetic field lines passing through the magnetic flux concentration space 327 pass through the magnetic flux concentration member 325 which is a ferromagnetic body covering a part of the grinding wheel 320. Therefore, the magnetic flux concentration member 325 guides the magnetic flux lines flowing from the upper surface of the first annular magnet 322b to the lower surface of the second annular magnet 323b to the magnetic flux concentration space 327. Therefore, the magnetic flux concentration space 327 The magnetic flux density becomes larger. That is, by attaching the magnetic flux concentration member 325 to the first magnetic field formation member 322 and the second magnetic field formation member 323, the magnetic flux concentration space 327 is increased, and the magnetic flux concentration space 327 is added to the polishing slurry 324. Effect of holding power.

Therefore, the manufacturing method of the glass plate of this modification uses the magnetic flux concentration member 325 to increase the holding force of the polishing slurry 324 that grinds the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92 .

(4-2) Modification B

As shown in FIG. 5, the magnetic flux concentration member 25 of this embodiment includes an upper concentration member 25 a, a lower concentration member 25 b, a first side concentration member 25 c, and a second side concentration member 25 d. However, the magnetic flux concentration member 25 may further include a spacer which is sandwiched between the first magnetic field forming member 22 and the second magnetic field forming member 23.

FIG. 14 is a sectional view of a grinding wheel 420 according to this modification. FIG. 15 is a part of a sectional view of the grinding wheel 420. FIG. 16 is a part of a sectional view of the grinding wheel 420, and is a diagram showing 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. Note that in FIG. 16, hatching is omitted in order to make the magnetic field lines stand out.

In this modification, the grinding wheel 420 mainly includes a rotation shaft 421, a first magnetic field forming member 422, a second magnetic field forming member 423, a polishing slurry 424, and a magnetic flux concentration member 425. The rotation shaft 421 and the polishing slurry 424 are in phase with the rotation shaft 21 and the polishing slurry 24 of this embodiment, respectively. The description is omitted here. The first magnetic field forming member 422 includes a first center member 422a and a first ring-shaped magnet 422b. The second magnetic field forming member 423 includes a second center member 423a and a second ring-shaped 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, is sandwiched between the first magnetic field forming member 422 and the second magnetic field forming member 423, and is penetrated by the rotation shaft 421. The intermediate member 425e has a cylindrical shape in which a hole penetrated by the rotation shaft 421 is formed. The outer peripheral surface of the intermediate member 425e is located at the same position as the outer peripheral surfaces of the first magnetic field forming member 422 and the second magnetic field forming member 423 in the radial direction. Furthermore, the intermediate member 425e located between the first side concentrated member 425c and the second side concentrated member 425d is preferably a ferromagnetic body, and may also be the first side concentrated member 425c and the second side concentrated member 425d At least one of them is integrally formed.

The first side concentrated 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 concentrated member 425c. The first inclined surface 425g is a plane 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 radially innermost side of the first inclined surface 425g coincides with the middle point between the upper end and the lower end of the outer peripheral surface of the intermediate member 425e.

The second side concentrated 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 concentrated member 425d. The second inclined surface 425i is a plane inclined upward in the vertical direction from the upper end of the second side surface 425h toward the radially inner side. The point on the radially innermost side of the second inclined surface 425i coincides with the middle point between the upper end and the lower end of the outer peripheral surface of the intermediate member 425e.

The point radially inward of the first inclined surface 425g of the first side concentrated member 425c coincides with the point radially inward of the second inclined surface 425i of the second side concentrated member 425d. As a result, as shown in FIG. 15, a magnetic flux concentration groove 426 is formed as a V-shaped groove on the outer peripheral surface of the magnetic flux concentration member 425. The polishing slurry 424 is held in a space inside the magnetic field forming groove 426. The magnetic flux concentration space 427.

As shown in FIG. 16, in this modification, a part of the magnetic field lines flowing upward from the upper surface of the first ring-shaped magnet 422 b passes through the upper concentrated member 425 a, the first side concentrated member 425 c, and the magnetic flux concentration space in this order. 427. The second side concentrated member 425d and the lower concentrated member 425b reach the lower surface of the second annular magnet 423b. Further, the magnetic field lines flowing 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 as a ferromagnetic body covering the grinding wheel 420. Therefore, the magnetic flux concentrating member 425 is formed as a magnetic circuit of magnetic lines of force flowing from the upper surface of the first annular magnet 422b to the lower surface of the second annular magnet 423b. The magnetic flux concentration member 425 guides the magnetic flux lines to the magnetic flux concentration space 427 to increase the magnetic flux density of the magnetic flux concentration space 427. That is, by attaching the magnetic flux concentration member 425 to the first magnetic field formation member 422 and the second magnetic field formation member 423, the magnetic flux density of the magnetic flux concentration space 427 is increased, and the magnetic flux concentration space 427 is added to the polishing slurry. Effect of holding power of 424.

Therefore, the manufacturing method of the glass plate of this modification uses the magnetic flux concentration member 425 to increase the holding force of the polishing slurry 424 that grinds the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92 .

(4-3) Modification C

As shown in FIG. 5, the magnetic flux concentration member 25 of this embodiment includes an upper concentration member 25 a, a lower concentration member 25 b, a first side concentration member 25 c, and a second side concentration member 25 d. However, the magnetic flux concentration member 25 may further include a spacer sandwiched between the first magnetic field forming member 22 and the second magnetic field forming member 23, and may not include the upper concentrated member 25a and the lower concentrated member 25b.

FIG. 17 is a sectional view of a grinding wheel 520 according to this modification. FIG. 18 is a part of a sectional view of the grinding wheel 520. FIG. 19 is a part of a sectional view of the grinding wheel 520, and is a diagram showing a magnetic field formed by the grinding wheel 520. In FIGS. 18 and 19, the polishing slurry 524 and the glass plate are omitted. 92. Note that in FIG. 19, hatching is omitted to make the magnetic field lines stand out. The polishing wheel 520 has a configuration in which the polishing wheel 320 of the modified example A and the polishing wheel 420 of the modified example B are combined.

In this modification, the grinding wheel 520 mainly includes a rotation 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. The rotation shaft 521 and the polishing slurry 524 are respectively the same as the rotation shaft 21 and the polishing slurry 24 in this embodiment, and therefore descriptions thereof are omitted. The first magnetic field forming member 522 includes a first center member 522a and a first ring-shaped magnet 522b. The second magnetic field forming member 523 includes a second center member 523a and a second ring-shaped magnet 523b. The magnetic flux concentration member 525 includes a first side concentration member 525c and a second side concentration member 525d. That is, the magnetic flux concentrating member 525 has a configuration in which an intermediate member 525e is added to the magnetic flux concentrating member 25 of this embodiment, and the upper and lower concentrating members 25a and 25b are removed. The intermediate member 525e is a steel plate such as stainless steel, is sandwiched between the first magnetic field forming member 522 and the second magnetic field forming member 523, and is penetrated by the rotation shaft 521. The intermediate member 525e has a cylindrical shape in which a hole penetrated by the rotation shaft 521 is formed. The outer peripheral surface of the intermediate member 525e is located at the same position as the outer peripheral surfaces of the first magnetic field forming member 522 and the second magnetic field forming member 523 in the radial direction. Furthermore, the intermediate member 525e located between the first side concentrated member 525c and the second side concentrated member 525d is preferably a ferromagnetic body, and may be the same as the first side concentrated member 525c and the second side concentrated member 525d. At least one of them is integrally formed.

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

The second side concentrated 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 concentrated member 525d. The second inclined surface 525i is a plane inclined upward in the vertical direction from the upper end of the second side surface 525h toward the radially inner side. 2nd inclined surface The point on the radially innermost side of 525i coincides with the point between the upper end and the lower end of the outer peripheral surface of the intermediate member 525e.

The point on the radially innermost side of the first inclined surface 525g of the first side concentrated member 525c coincides with the point on the radially innermost side of the second inclined surface 525i of the second side concentrated member 525d. As a result, as shown in FIG. 18, a magnetic flux concentration groove 526 is formed as a V-shaped groove on the outer peripheral surface of the magnetic flux concentration member 525. The polishing slurry 524 is held in a magnetic flux concentration space 527 which is a space inside the magnetic field forming groove 526.

As shown in FIG. 19, in this modification, a part of the magnetic field lines flowing upward from the upper surface of the first annular magnet 522b passes through the first side concentrated member 525c, the magnetic flux concentrated space 527, and the second side in this order. The part concentrating member 525d reaches the lower surface of the second ring-shaped magnet 523b. Furthermore, the magnetic field lines flowing 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 which is a ferromagnetic body covering a part of the grinding wheel 520. Therefore, the magnetic flux concentrating member 525 is formed as a magnetic circuit of magnetic lines of force flowing from the upper surface of the first annular magnet 522b to the lower surface of the second annular magnet 523b. The magnetic flux concentration member 525 increases the magnetic flux density of the magnetic flux concentration space 527 by guiding the magnetic field lines to the magnetic flux concentration space 527. That is, by mounting the magnetic flux concentration member 525 on the first magnetic field formation member 522 and the second magnetic field formation member 523, the magnetic flux concentration of the magnetic flux concentration space 527 is increased, and the magnetic flux concentration space 527 is added to the polishing slurry Effect of holding power of 524.

Therefore, the manufacturing method of the glass plate of this modification uses the magnetic flux concentrating member 525 to improve the holding force of the polishing slurry 524 for polishing the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92 .

(4-4) Modification D

The magnetic flux concentration member 25 of this embodiment includes an upper concentration member 25a and a lower concentration member 25b. As shown in FIG. 5, the upper concentrated member 25a covers both the upper surface of the first center member 22a and the upper surface of the first ring-shaped magnet 22b, and the lower concentrated member 25b covers the second Both the lower surface of the center member 23a and the lower surface of the second annular magnet 23b. However, the upper concentrated member 25a may not cover the upper surface of the first center member 22a, and the lower concentrated member 25b may not cover the lower surface of the second center member 23a.

FIG. 20 is a cross-sectional view of a grinding wheel 20 according to this modification. In FIG. 20, the constituent elements other than the upper concentrated member 25a and the lower concentrated member 25b are the same as the present embodiment. The upper concentrated member 25a covers only the upper surface of the first ring-shaped magnet 22b of the first magnetic field forming member 22 and the upper surface of the first side concentrated member 25c. The lower concentrated member 25b covers only the lower surface of the second ring-shaped magnet 23b of the second magnetic field forming member 23 and the lower surface of the second side concentrated member 25d.

In this modification, as in FIG. 6 of the present embodiment, 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 covering a part of the grinding wheel 20. Therefore, by mounting the magnetic flux concentration member 25 on the first magnetic field formation member 22 and the second magnetic field formation member 23, the magnetic flux density of the magnetic flux concentration space 27 is increased, and the magnetic flux concentration space 27 is increased to the polishing slurry. 24 retention effect.

Therefore, the manufacturing method of the glass plate of this modification uses the magnetic flux concentrating member 25 to improve the holding force of the polishing slurry 24 that grinds the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92 .

Furthermore, the upper concentrated member 25a and the lower concentrated member 25b of this modification can be applied to the modifications A to C.

The first center member 22a and the second center member 23a may be integrated members, and the first ring-shaped magnet 22b and the second ring-shaped magnet 23b may be integrated members.

(4-5) Modification E

The magnetic flux concentrating member 25 of this embodiment includes a first side concentrated member 25c and a second side concentrated member 25d. A magnetic flux concentration groove 26 is formed on the outer peripheral surface of the magnetic flux concentration member 25 as a V-shaped groove. However, a groove other than a V-shape may be formed on the outer peripheral surface of the magnetic flux concentration member 25.

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

The first side concentrated member 25c includes a first side surface 25e and a first curved surface 25f. The first side surface 25e is the outer peripheral surface of the first side concentrated member 25c. The first curved surface 25f is a surface curved downward from the lower end of the first side surface 25e toward the inside in the radial direction and downward in the vertical direction. The point on the radially innermost side of the first curved surface 25f coincides with the lower end of the outer peripheral surface of the first magnetic field forming member 22.

The second side concentrated 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 portion concentrating member 25d. The second curved surface 25h is a surface that is curved upward from the upper end of the second side surface 25g toward the inside in the radial direction and upward in the vertical direction. The point on the radially innermost side of the second curved surface 25h coincides with the upper end of the outer peripheral surface of the second magnetic field forming member 23.

As shown in FIG. 21, the point closest to the radially inner side of the first curved surface 25f of the first side concentrated member 25c coincides with the point closest to the radially inner side of the second curved surface 25h of the second side concentrated member 25d. . As a result, as shown in FIG. 21, a magnetic flux concentration groove 26 is formed on the outer peripheral surface of the magnetic flux concentration member 25. The magnetic flux concentration groove 26 is a groove including a first curved surface 25f and a second curved surface 25h. The magnetic flux concentration space 27 which is a space inside the magnetic flux concentration groove 26 is a space for holding the polishing slurry 24.

In this modification, as in FIG. 6 of the present embodiment, 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 covering a part of the grinding wheel 20. Therefore, by mounting the magnetic flux concentration member 25 on the first magnetic field formation member 22 and the second magnetic field formation member 23, the magnetic flux density of the magnetic flux concentration space 27 is increased, and the magnetic flux concentration space 27 is increased to the polishing slurry. 24 retention effect.

Therefore, the manufacturing method of the glass plate of this modification uses the magnetic flux concentrating member 25 to improve the holding force of the polishing slurry 24 that grinds the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92 .

Furthermore, the first side concentrated member 25c and the second side concentrated member of the present modification can be combined. 25d is applied to variations A to D.

(4-6) Modification F

The magnetic flux concentrating member 25 of this embodiment includes a first side concentrated member 25c and a second side concentrated member 25d. A magnetic flux concentration groove 26 is formed on the outer peripheral surface of the magnetic flux concentration member 25 as a V-shaped groove. The most radially inward point of the magnetic flux concentration groove 26 is located on the outer peripheral surfaces of the first magnetic field forming member 22 and the second magnetic field forming member 23. However, the most radially inward point of the magnetic flux concentration groove 26 may not be located on the outer peripheral surfaces of the first magnetic field forming member 22 and the second magnetic field forming member 23.

FIG. 22 corresponds to FIG. 6 of the present embodiment, and is a part of a cross-sectional view of the grinding wheel 20 according to this modification. In FIG. 22, the constituent elements other than the first side concentrated member 25c and the second side concentrated member 25d are the same as those of the present embodiment.

The first side concentrated member 25c includes a first side surface 25e and a first inclined surface 25f. The first side surface 25e is the outer peripheral surface of the first side concentrated member 25c. The first inclined surface 25f is a plane inclined downward from the lower end of the first side surface 25e toward the inside in the radial direction and downward in the vertical direction. The point of the first inclined surface 25f that is closest to the radially inner side is further radially outward than the lower end of the outer peripheral surface of the first magnetic field forming member 22.

The second side concentrated 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 portion concentrating member 25d. The second inclined surface 25h is a plane inclined upward from the upper end of the second side surface 25g toward the inside in the radial direction and upward in the vertical direction. The position of the second inclined surface 25h closest to the radially inner side is further radially outward from the upper end of the outer peripheral surface of the second magnetic field forming member 23.

As shown in FIG. 22, the point closest to the radially inner side of the first inclined surface 25f of the first side concentrated member 25c coincides with the point positioned most radially inward of the second inclined surface 25h of the second side concentrated member 25d . As a result, as shown in FIG. 22, a magnetic flux concentration groove 26 is formed on the outer peripheral surface of the magnetic flux concentration member 25. The position of the magnetic flux concentration groove 26 that is closest to the radially inner side is further radially outward than the outer peripheral surfaces of the first magnetic field forming member 22 and the second magnetic field forming member 23. Inside the magnetic flux concentration groove 26 The magnetic flux concentration space 27 in this space is a space for holding the polishing slurry 24.

In this modification, as in FIG. 6 of the present embodiment, the magnetic field lines passing through the magnetic flux concentration space 27 pass through the magnetic flux concentration member 25 as a ferromagnetic body covering the grinding wheel 20. Therefore, by mounting the magnetic flux concentration member 25 on the first magnetic field formation member 22 and the second magnetic field formation member 23, the magnetic flux density of the magnetic flux concentration space 27 is increased, and the magnetic flux concentration space 27 is increased to the polishing slurry. 24 retention effect.

Therefore, the manufacturing method of the glass plate of this modification uses the magnetic flux concentrating member 25 to improve the holding force of the polishing slurry 24 that grinds the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92 .

Furthermore, the first side concentrated member 25c and the second side concentrated member 25d of this modification can be applied to the modifications A to E.

(4-7) Modification G

The magnetic flux concentration member 425 of the modification B includes a first side concentration member 425c and a second side concentration member 425d. A magnetic flux concentration groove 426 is formed on the outer peripheral surface of the magnetic flux concentration member 425 as a V-shaped groove. The most radially inward point of the magnetic flux concentration groove 426 is located on the outer peripheral surfaces of the first magnetic field forming member 422 and the second magnetic field forming member 423. However, the most radially inward point of the magnetic flux concentration groove 426 may not be located on the outer peripheral surfaces of the first magnetic field forming member 422 and the second magnetic field forming member 423.

FIG. 23 corresponds to FIG. 15 of the modified example B, and is a part of a sectional view of the grinding wheel 420 of the modified example. In FIG. 23, the components other than the first side concentrated member 425 c and the second side concentrated member 425 d are the same as those of the modified example B.

The first side concentrated 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 concentrated member 425c. The first inclined surface 425g is a plane inclined downward from the lower end of the first side surface 425f toward the inside in the radial direction and downward in the vertical direction. The point of the first inclined surface 425g closest to the radially inner side is located radially inward of the lower end of the outer peripheral surface of the first magnetic field forming member 422.

The second side concentrated 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 concentrated member 425d. The second inclined surface 425i is a plane inclined upward in the vertical direction from the upper end of the second side surface 425h toward the radially inner side. The position of the second inclined surface 425i that is closest to the radially inner side is further radially inward than the upper end of the outer peripheral surface of the second magnetic field forming member 423.

As shown in FIG. 23, the point closest to the radially inner side of the first inclined surface 425g of the first side concentrated member 425c coincides with the point closest to the radially inner side of the second inclined surface 425i of the second side concentrated member 425d. . As a result, as shown in FIG. 23, a magnetic flux concentration groove 426 is formed on the outer peripheral surface of the magnetic flux concentration member 425. The magnetic flux concentration groove 426 is a groove including a first inclined surface 425g and a second inclined surface 425i. The position of the magnetic flux concentration groove 426 that is most radially inward is radially inward of the outer peripheral surfaces of the first magnetic field forming member 422 and the second magnetic field forming member 423. The magnetic flux concentration space 427 which is a space inside the magnetic flux concentration groove 426 is a space for holding the polishing slurry 424.

In this modification, as in FIG. 15 of modification B, the magnetic field lines passing through the magnetic flux concentration space 427 pass through the magnetic flux concentration member 425 as a ferromagnetic body covering the grinding wheel 420. Therefore, by mounting the magnetic flux concentration member 425 on the first magnetic field formation member 422 and the second magnetic field formation member 423, the magnetic flux density of the magnetic flux concentration space 427 is increased, and the magnetic flux concentration space 427 is added to the polishing slurry. Effect of holding power of 424.

Therefore, the manufacturing method of the glass plate of this modification uses the magnetic flux concentrating member 425 to improve the holding force of the polishing slurry 424 that grinds the end surface 92a of the glass plate 92, thereby improving the polishing efficiency of the end surface 92a of the glass plate 92 .

The first side concentrated member 425c and the second side concentrated member 425d of the present modification can be similarly applied to the modification C.

(4-8) Modification H

The polishing apparatus 10 of this embodiment polishes the end surface 92a of the glass plate 92. However, the polishing device 10 may polish the end surfaces of other plate-shaped articles such as metal plates and ceramic plates.

(5) Examples

Next, an example of the manufacturing method of the glass plate of this embodiment is demonstrated.

[Example 1]

The end surface 92a of the glass plate 92 is ground using the grinding apparatus 10 provided with the grinding wheel 20 of this embodiment. Then, when the grinding wheel 20 grinds the end surface 92a, the magnetic flux density at the point most radially inward of the end surface 92a is measured.

The grinding wheel 120 of the first comparative example shown in FIG. 8, the grinding wheel 220 of the second comparative example shown in FIG. 10, the grinding wheel 320 of the modified example A shown in FIG. 12, and the changes shown in FIG. 14. The same measurement was performed on the grinding wheel 420 of Example B and the grinding wheel 520 of Modification C shown in FIG. 17 respectively.

In the entire grinding wheel used in this example, the first magnetic field forming member and the second magnetic field forming member have 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 the measured magnetic flux density is Tesla (T). As shown in the table, it was confirmed that the value of the magnetic flux density measured when the grinding wheel 20 of this embodiment was used was the highest. In addition, it was confirmed that the values of the magnetic flux density measured when using the grinding wheel 20 of this embodiment, the grinding wheel 320 of modification A, the grinding wheel 420 of modification B, and the grinding wheel 520 of modification C were compared with those of the first comparative example. The grinding wheel 120 and the grinding wheel 220 of the second comparative example have high magnetic flux density values measured at the time.

[Example 2]

The polishing device 10 provided with the polishing wheel 420 of the modification B is used to face the end surface of the glass plate 92 92a is ground. Then, when the grinding wheel 420 grinds the end surface 92a, the magnetic flux density at the point most radially inward of the end surface 92a is measured.

In addition, like the grinding wheels of the modified examples F and G, the same measurement is performed on a plurality of kinds of grinding wheels whose radial positions of the innermost points are different from the grinding wheels 420. Here, the “innermost point” refers to a point on the radially innermost side of the magnetic flux concentration groove 426 formed on the outer peripheral surface of the magnetic flux concentration member 425 of the grinding wheel 420.

The radial position of the innermost point is measured based on the radial position of the reference point. Here, the "reference point" refers to 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 of Modification F, when the innermost point is radially outward from the reference point, the radial position of the innermost point is defined as having a positive value. As shown in FIG. 23 of the modified example 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.

The radial position of the innermost point is measured by setting the radial position of the reference point to zero. For example, when the radial position of the innermost point is "+ 1mm", the innermost point is located at a position that moves 1mm from the reference point to the radially outer side, and the radial position of the innermost point is "-1mm" In the case of "", the innermost point is located at a position that moves 1 mm radially inward from the reference point.

In the entire grinding wheel used in this example, the first magnetic field forming member and the second magnetic field forming member have 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 the measured magnetic flux density is Tesla (T). As shown in the table, it was confirmed that the value of the magnetic flux density measured when using the grinding wheel with a radial position of 0 mm at the innermost point, that is, the grinding wheel 420 of this modification B, was the highest.

[Example 3]

The end surface 92a of the glass plate 92 is repeatedly polished using the grinding wheel 20 of this embodiment, and the arithmetic average roughness Ra of the end surface 92a after the polishing is measured.

In addition, the end surface 92a of the glass plate 92 was repeatedly polished using the polishing wheel 120 of the first comparative example, and the arithmetic average roughness Ra of the end surface 92a after polishing was measured.

In the entire grinding wheel used in this example, the first magnetic field forming member and the second magnetic field forming member have an outer diameter of 125 mm, an inner diameter of 90 mm, and a vertical dimension of 10 mm. In addition, the thickness of the glass plate 92 used in this embodiment is 0.5 mm, the rotation speed of the grinding wheel is 2000 revolutions per minute, and the conveying speed of the glass plate 92 is 2400 mm per minute.

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

Based on the above description, in this embodiment, the arithmetic average roughness Ra of the end surface 92a can be reduced to 10 nm or less by two grinding operations, and cracks (microcracks or horizontal cracks) can be removed from the end surface 92a.

The end surface 92a before the grinding process is obtained by the following steps. First, the glass plate 92 is cut into a specific size by mechanical scribing using a cutting wheel. Secondly, for glass plates The cutting surface 92, that is, the end surface 92a, is ground using a metal bonding diamond wheel. Thereby, a desired shape of the end surface 92a is formed in a short time. Next, the end surface 92a is ground using a resin-bonded diamond wheel pair. Thereby, the process of making the shape of the end surface 92a uniform and making the surface roughness of the end surface 92a small is performed. Through the above steps, an end face 92a having a processed deteriorated layer of less than 3 μm is finally obtained.

In these examples, the grinding wheel 20 of this embodiment is used to polish the end surface 92a of the glass plate 92 cut by laser. The end surface 92a of the glass plate 92 cut by a laser has a corner portion having a substantially right-angled cross section. On the other hand, the end surface 92a after being grinded by the grinding wheel 20 has a corner portion having an R-shaped cross section, and an end surface 92a having an R-shaped curvature radius of less than 10 μm is obtained.

Claims (10)

A manufacturing method of a glass plate, comprising a magnetic abrasive grain containing a first magnetic field forming member and a second magnetic field forming member, and holding a magnetic field formed by the first magnetic field forming member and the second magnetic field forming member, and The first magnetic field forming member and the second magnetic field forming member rotate together about a rotation axis. In this state, the ends of the glass plate are brought into contact with the magnetic abrasive grains, the ends are polished, and the first magnetic field is formed. The member and the second magnetic field forming member include a cylindrical magnet in which the rotation shaft penetrates the upper and lower surfaces and a side surface around the rotation shaft, and is magnetized along the rotation shaft. The end portion is formed in The first magnetic field forming member and the second magnetic field forming member are ground in the grinding space on the side surface, and magnetic flux concentration members are mounted on the upper surface, the lower surface, and the side surfaces. The magnetic lines of force flowing from the upper surface or the lower surface are introduced into the magnetic body of the grinding space. The method for manufacturing a glass plate according to claim 1, wherein a space between the first magnetic field forming member and the second magnetic field forming member, and a diameter of the rotation axis of the first magnetic field forming member and the second magnetic field forming member. In at least one of the outward spaces, the density of the magnetic flux is increased by the magnetic flux concentration member. The method for manufacturing a glass plate according to claim 2, wherein the space of the second magnetic field forming member opposite to the side on which the first magnetic field forming member is located, and the first magnetic field forming member is formed with respect to the second magnetic field. In at least one of the spaces on the opposite side of the member, the magnetic flux density increases due to the magnetic flux concentration member. A polishing device for a glass plate, comprising: a rotating shaft; a first magnetic field forming member connected to the rotating shaft and rotating around the rotating shaft; and a second magnetic field forming member connected to the rotating shaft and rotating around the rotating shaft Shaft rotation; magnetic abrasive grains held by the magnetic field formed by the first magnetic field forming member and the second magnetic field forming member; and a magnetic flux concentration member mounted on the first magnetic field forming member and the second magnetic field Forming a magnetic body on the member to concentrate the magnetic flux from the first magnetic field forming member toward the second magnetic field forming member, thereby increasing the density of the magnetic flux; and the density of the magnetic flux by the magnetic flux concentration member The magnetic abrasive particles held in the increased space are rotated about the rotation axis together with the first magnetic field forming member and the second magnetic field forming member, and in this state contact the end portion of the glass plate to perform the end portion. Grinding. The polishing device for a glass plate according to claim 4, wherein the magnetic flux concentration member is in a space between the first magnetic field forming member and the second magnetic field forming member, and the first magnetic field forming member and the second magnetic field forming member. The density of the magnetic flux is increased in at least one of the spaces radially outside the rotation axis. The grinding device for a glass plate according to claim 4 or 5, wherein the magnetic flux concentration member is installed at least radially outward of the rotation axis of the first magnetic field formation member and the second magnetic field formation member, and has a magnetic flux concentration groove. The magnetic flux concentration groove is a groove that is at a right angle to a central axis of the rotation axis in a surface on a radially outer side of the rotation axis of the magnetic flux concentration member. The polishing device for a glass plate according to claim 6, wherein the magnetic flux concentration member is further mounted on each of the first magnetic field forming member and the second magnetic field forming member in a center axis direction of the rotation axis. The polishing device for a glass plate according to claim 6, wherein the first magnetic field forming member is adjacent to the second magnetic field forming member in a center axis direction of the rotation axis. For example, the glass plate polishing device according to claim 6, wherein the first magnetic field forming member and the second magnetic field forming member have the same cylindrical shape, and the central axes of the first magnetic field forming member and the second magnetic field forming member are located On the center axis of the rotation axis, the distance between the magnetic flux concentration groove located at the innermost point in the radial direction of the rotation axis and the center axis of the rotation axis is equal to the first magnetic field forming member and the second magnetic field. Form the outer diameter of the component. The polishing device for a glass plate according to claim 6, wherein the magnetic flux concentration member increases the density of the magnetic flux in an inner space of the magnetic flux concentration groove.