Top roll, glass plate manufacturing apparatus, and glass plate manufacturing method

Abstract

The present invention provides a top roll, a glass plate manufacturing apparatus, and a manufacturing method that can suppress dust from falling from the first insulating material onto the glass ribbon and reduce the drawbacks of the glass ribbon. [Solution] The top roll 33 supports the glass ribbon GR. The top roll 33 comprises a rotating roll 331 that contacts the upper surface of the glass ribbon GR, a rotating shaft 332 that rotates the rotating roll, a first heat insulating material 333 that covers the outer circumferential surface of the rotating shaft 332, and a first graphite sheet 334 that covers the outer circumferential surface of the first heat insulating material 333.

Description

[Technical Field]

[0001] This disclosure relates to a top roll, a glass plate manufacturing apparatus, and a glass plate manufacturing method. [Background technology]

[0002] The float process is a known method for manufacturing glass plates. In the float process, molten glass is continuously supplied onto the surface of molten metal, and the molten glass is formed into a strip on the surface of the molten metal. The glass formed into a strip is also called a glass ribbon. The glass ribbon flows in a predetermined direction on the surface of the molten metal, gradually cooling and solidifying.

[0003] The thickness of a glass ribbon is determined by the balance between gravity and surface tension, unless an external force is applied to the ribbon. To form a glass ribbon thinner than the equilibrium thickness, a top roll is used (see, for example, Patent Document 1). The top roll is provided on both sides of the glass ribbon in the width direction and applies tension in the width direction of the glass ribbon. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-239370 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The top roll comprises a rotating roll that contacts the upper surface of the glass ribbon and a rotating shaft that rotates the rotating roll. The rotating roll and rotating shaft have internal passages for a coolant. For example, water is used as the coolant. The coolant absorbs heat from the rotating roll and rotating shaft and discharges the absorbed heat to the outside of the molding furnace, thereby maintaining the temperature of the rotating roll and rotating shaft below the heat resistance temperature.

[0006] The top roll is equipped with a first insulating material that covers the outer surface of the rotating shaft. The first insulating material restricts heat transfer between the rotating shaft and the glass ribbon, suppressing overheating of the rotating shaft and inhibiting the cooling and solidification of the glass ribbon. By suppressing the cooling and solidification of the glass ribbon, the rotating roll can easily bite into the glass ribbon, and sufficient tension can be applied to the glass ribbon.

[0007] By the way, if the top roll is equipped with a first insulation material, the first insulation material may deteriorate due to heat and generate dust. If this dust falls onto the glass ribbon, it can cause defects in the glass ribbon.

[0008] One aspect of this disclosure provides a technique for reducing the defects of glass ribbons. [Means for solving the problem]

[0009] A top roll according to one aspect of the present disclosure supports a glass ribbon. The top roll comprises a rotating roll in contact with the upper surface of the glass ribbon, a rotating shaft for rotating the rotating roll, a first heat insulating material covering the outer circumferential surface of the rotating shaft, and a first graphite sheet covering the outer circumferential surface of the first heat insulating material. [Effects of the Invention]

[0010] According to one aspect of this disclosure, by providing a first graphite sheet with excellent thermal shock resistance on the outer surface of the first heat-insulating material, it is possible to suppress dust falling from the first heat-insulating material onto the glass ribbon, thereby reducing the drawbacks of the glass ribbon. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a cross-sectional view showing a glass plate manufacturing apparatus according to one embodiment. [Figure 2] Figure 2 is a cross-sectional view showing an example of a molding apparatus. [Figure 3] Figure 3 is a plan view showing an example of the arrangement of the top rolls. [Figure 4] Figure 4 is a cross-sectional view showing an example of the structure of a top roll. [Figure 5] FIG. 5 is a diagram showing an example of an adhesive layer. [Figure 6] FIG. 6 is a diagram showing an example of a third graphite sheet. [Figure 7] FIG. 7 is a perspective view showing an example of a third graphite sheet. [Figure 8] FIG. 8 is a diagram showing an example of a cut of a third graphite sheet. **DETAILED DESCRIPTION OF THE INVENTION**

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and the description thereof may be omitted. In each drawing, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other, the X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is a vertical direction. The X-axis direction is the conveyance direction of the glass ribbon GR, and the Y-axis direction is the width direction of the glass ribbon GR. In the specification, "~" indicating a numerical range means that the numerical values described before and after it are included as the lower limit value and the upper limit value. The numerical range includes the rounded range.

[0013] First, referring to FIG. 1, a glass plate manufacturing apparatus 1 according to an embodiment will be described. The glass plate manufacturing apparatus 1 manufactures a glass plate by the float method. The glass plate is, for example, non-alkali glass, aluminosilicate glass, borosilicate glass, or soda lime glass. Non-alkali glass means glass that does not substantially contain alkali metal oxides such as Na2O and K2O. Here, not substantially containing alkali metal oxides means that the total content of alkali metal oxides is 0.1 mass% or less.

[0014] The use of the glass plate is not particularly limited, but for example, it is a cover glass for a display (for example, a liquid crystal display or an organic EL display). When the use of the glass plate is a cover glass, the glass plate is chemically strengthened glass. Chemically strengthened glass contains alkali metal oxides, unlike non-alkali glass.

[0015] The thickness of the glass plate is selected according to the use of the glass plate. When the use of the glass plate is a cover glass for a display, the thickness of the glass plate is, for example, 0.1 mm to 5.0 mm. When the use of the glass plate is a glass substrate for a display, the thickness of the glass plate is, for example, 0.1 mm to 0.7 mm. When the use of the glass plate is an automobile windshield, the thickness of the glass plate is, for example, 0.2 mm to 3.0 mm.

[0016] The glass plate manufacturing apparatus 1 includes, for example, a melting apparatus 2, a forming apparatus 3, and a slow cooling apparatus 4 in this order.

[0017] The melting apparatus 2 includes, for example, a melting furnace 21 that houses molten glass G, and a burner 22 that forms a flame above the molten glass G housed in the melting furnace 21. The glass raw material charged into the melting furnace 21 gradually melts into the molten glass G by the radiant heat from the flame formed by the burner 22. The molten glass G is continuously conveyed from the melting apparatus 2 to the forming apparatus 3. The heating source is not limited to the burner 22, and may be an electric heater or an electrode, etc. The electrode generates heat in the molten glass G by passing an electric current through the molten glass G.

[0018] The forming apparatus 3 includes a forming furnace 31, and forms the molten glass G into a desired shape inside the forming furnace 31. The forming furnace 31 has, for example, a bath 311. The bath 311 houses molten metal M. As the molten metal M, for example, molten tin is used. In addition to molten tin, a molten tin alloy, etc. can also be used, and the molten metal M may have a density higher than that of the molten glass G. The molten glass G is continuously supplied onto the molten metal M, and is formed into a strip-shaped glass ribbon GR using the smooth liquid surface of the molten metal M.

[0019] The molding furnace 31 has a ceiling 312 above the bathtub 311. The inside of the molding furnace 31 is filled with a reducing gas and maintained at a pressure higher than atmospheric pressure to prevent oxidation of the molten metal M. The reducing gas is, for example, a mixture of nitrogen gas and hydrogen gas, containing 85% to 98.5% by volume of nitrogen gas and 1.5% to 15% by volume of hydrogen gas. The reducing gas is supplied through the joints between the bricks of the ceiling 312 and through holes in the ceiling 312.

[0020] The molding apparatus 3 includes a heater 32 for heating the glass ribbon GR. The heater 32 is suspended, for example, from the ceiling 312 of the molding furnace 31 and heats the glass ribbon GR as it passes below. The heater 32 is, for example, an electric heater and is heated by energization. Multiple heaters 32 are arranged in a matrix in the transport direction and width direction of the glass ribbon GR. By controlling the output of the multiple heaters 32, the temperature distribution of the glass ribbon GR can be controlled, and the thickness distribution of the glass ribbon GR can be controlled.

[0021] The annealing device 4 anneales the glass ribbon GR formed in the molding device 3. The annealing device 4 includes, for example, a heat treatment furnace and conveying rolls that transport the glass article in a desired direction inside the heat treatment furnace. The conveying rolls are arranged in multiples, for example, at intervals in the horizontal direction. The glass ribbon GR is annealed as it is transported from the inlet to the outlet of the heat treatment furnace. By annealing the glass ribbon GR, residual strain can be reduced.

[0022] The slow cooling device 4 comprises a dross box 41 and a lift-out roll 42. The dross box 41 is an example of a heat treatment furnace. The lift-out roll 42 is positioned inside the dross box 41 and lifts the glass ribbon GR from the molten metal M. The lift-out roll 42 is an example of a conveying roll. Multiple lift-out rolls 42 are arranged at intervals in the conveying direction (X-axis direction) of the glass ribbon GR. The number of lift-out rolls 42 is not particularly limited. The lift-out roll 42 is rotationally driven by a drive device such as a motor (not shown), and the driving force conveys the glass ribbon GR diagonally upward. The axial direction of the lift-out roll 42 is the same as the width direction (Y-axis direction) of the glass ribbon GR.

[0023] The slow cooling device 4 may be equipped with a heater (not shown) on the ceiling of the dross box 41 to adjust the temperature of the glass ribbon GR. The heater may be provided not only above the glass ribbon GR but also below it. Inside the dross box 41, the temperature of the glass ribbon GR is preferably (Tg-50)°C to (Tg+30)°C, with respect to the glass transition point Tg of the glass ribbon GR.

[0024] The annealing device 4 comprises an annealing furnace 45 and layer rolls 46. The annealing furnace 45 is located downstream of the dross box 41. The annealing furnace 45 is an example of a heat treatment furnace. The layer rolls 46 are located inside the annealing furnace 45 and transport the glass ribbon GR in the longitudinal direction (X-axis direction) of the glass ribbon GR. The layer rolls 46 are an example of a transport roll. Multiple layer rolls 46 are provided at intervals in the transport direction of the glass ribbon GR. The number of layer rolls 46 is not particularly limited. The layer rolls 46 are rotationally driven by a drive device such as a motor (not shown), and the driving force transports the glass ribbon GR in the horizontal direction (X-axis direction). The axial direction of the layer rolls 46 is the same as the width direction (Y-axis direction) of the glass ribbon GR.

[0025] The annealing device 4 slowly cools the glass ribbon GR to a temperature below the strain point of the glass while conveying it with a layer roll 46. The annealing device 4 may be equipped with a heater (not shown) inside the annealing furnace 45 to adjust the temperature of the glass ribbon GR.

[0026] Next, with reference to Figure 2, the molding apparatus 3 will be described in detail. The molding apparatus 3 includes a molding furnace 31 that houses the molten glass G inside. The molding furnace 31 includes, for example, a bathtub 311, a ceiling 312, and side walls 313. The side walls 313 are provided above the bathtub 311. The side walls 313 have a brick layer 314 and a metal layer 315 provided outside the brick layer 314. The side walls 313 are provided on both sides in the width direction of the glass ribbon GR (positive Y-axis side and negative Y-axis side).

[0027] The molding apparatus 3 includes a top roll 33. The top roll 33 is inserted into the molding furnace 31 through a gap formed between the bath tub 311 and the side wall 313. The top roll 33 supports the glass ribbon GR. The top roll 33 is in contact with the upper surface of the glass ribbon GR, and the molten metal M is in contact with the lower surface of the glass ribbon GR. The upper surface of the glass ribbon GR is sometimes called the top surface. The lower surface of the glass ribbon GR is sometimes called the bottom surface.

[0028] As shown in Figure 3, a pair of top rolls 33 are provided on both sides of the glass ribbon GR in the width direction. The pair of top rolls 33 suppress the shrinkage of the glass ribbon GR in the width direction. The thickness of the glass ribbon GR can be made thinner than the equilibrium thickness. Multiple pairs of top rolls 33 are provided at intervals in the flow direction (X-axis direction) of the glass ribbon GR. The glass ribbon GR flows on the liquid surface of the molten metal M and is gradually cooled and solidified.

[0029] Next, the details of the top roll 33 will be described with reference to Figures 4 to 8. As shown in Figure 4, the top roll 33 comprises a rotating roll 331 that contacts the upper surface of the glass ribbon GR, and a rotating shaft 332 that rotates the rotating roll 331. The outer diameter of the rotating roll 331 is larger than the outer diameter of the rotating shaft 332, and the outer circumference of the rotating roll 331 contacts the upper surface of the glass ribbon GR. The outer circumference of the rotating shaft 332 does not contact the upper surface of the glass ribbon GR. The rotating roll 331 is provided at one end of the rotating shaft 332, and a drive source (not shown) is provided at the other end of the rotating shaft 332. The drive source includes a rotary motor. The drive source is provided outside the molding furnace 31.

[0030] The rotating roll 331 and the rotating shaft 332 have internal coolant passages, although these are not shown. For example, water is used as the coolant. The coolant absorbs heat from the rotating roll 331 and the rotating shaft 332 and discharges the absorbed heat to the outside of the molding furnace 31, thereby maintaining the temperature of the rotating roll 331 and the rotating shaft 332 below the heat resistance temperature. The rotating shaft 332 is, for example, constructed as a double pipe and has a forward passage for the coolant and a return passage for the coolant.

[0031] The top roll 33 is equipped with a first heat insulating material 333 that covers the outer surface of the rotating shaft 332. The outer diameter of the first heat insulating material 333 is smaller than the outer diameter of the rotating roll 331, and the outer surface of the first heat insulating material 333 does not come into contact with the upper surface of the glass ribbon GR. The first heat insulating material 333 restricts heat transfer between the rotating shaft 332 and the glass ribbon GR, suppressing overheating of the rotating shaft 332 and suppressing the cooling and solidification of the glass ribbon GR. By suppressing the cooling and solidification of the glass ribbon GR, the rotating roll 331 can easily bite into the glass ribbon GR, and sufficient tension can be applied to the glass ribbon GR. The first heat insulating material 333 is an insulating material.

[0032] The first heat-insulating material 333 preferably has a first base material 333a made of a porous material in order to suppress heat transfer. The first base material 333a is, for example, an aggregate of inorganic fibers and inorganic particles. The inorganic fibers and inorganic particles are composed of, for example, ceramic, glass, or carbon. The ceramic includes, for example, silicon oxide, aluminum oxide, or a compound of silicon oxide and aluminum oxide. The first base material 333a may further include an inorganic binder. The first base material 333a may also include a rope for bundling the above aggregates.

[0033] The first base material 333a preferably contains carbon. This is because even if dust from the first base material 333a adheres to the glass ribbon GR, the carbon dust will burn off in the annealing furnace 45. Unlike the molding furnace 31, the annealing furnace 45 is filled with air. The carbon dust reacts with oxygen in the air and gasifies. Therefore, even if carbon dust adheres to the glass ribbon GR, it hardly remains as a defect.

[0034] The first base material 333a is formed in a cylindrical shape. A through hole is formed in the center of the first base material 333a. The rotating shaft 332 is inserted through this through hole. Preferably, the first base material 333a covers the outer circumferential surface of the rotating shaft 332 over its entire circumference. The first base material 333a has an end face that contacts the rotating roll 331 (left face in Figure 4) and an end face that faces the opposite direction (right face in Figure 4).

[0035] The first heat-insulating material 333 has, for example, a first base material 333a and a first coating 333b in this order, extending from the radially inner side to the radially outer side of the rotating shaft 332. The first coating 333b is a hardened cement product. The first coating 333b covers the outer circumferential surface of the first base material 333a. Preferably, the first coating 333b also covers the end face of the first base material 333a opposite to the rotating roll 331. By wrapping the first base material 333a with the first coating 333b, dust falling from the first base material 333a onto the glass ribbon GR can be suppressed, and the drawbacks of the glass ribbon GR can be reduced.

[0036] The first coating 333b is a hardened cement product, as described above. The cement, for example, has hydraulic properties. The first coating 333b is obtained, for example, by applying a slurry containing cement to the first base material 333a, drying it, and then firing the dried slurry in the atmosphere. The firing temperature is preferably higher than the operating temperature of the top roll 33. The firing temperature is set appropriately depending on the material of the slurry, but is for example 1300°C to 1650°C.

[0037] The slurry is obtained, for example, by mixing aluminum oxide powder, hydraulic material powder, a porosity enhancer, and water. The hydraulic material is, for example, alumina cement, magnesia cement, or gypsum. Alumina cement contains calcium aluminate as its main component. Magnesia cement contains magnesium oxide and magnesium chloride.

[0038] The porosity-inducing material is, for example, expanded polystyrene, sawdust, or a foaming agent. The porosity-inducing material disappears when fired in the atmosphere, forming pores. The pores are formed between the framework containing aluminum oxide powder. The porosity of the first film 333b is, for example, 70% by volume or more. The bulk density of the first film 333b is 0.6 g / cm³. 3 ~1.2g / cm 3 That is the case.

[0039] The first coating 333b has excellent heat insulation properties and excellent strength. The thermal conductivity of the first coating 333b is, for example, 0.4 W / (m·°C) to 1.0 W / (m·°C) at 350°C. The thermal conductivity is measured by the hot-wire method described in JIS R2616:2001. The compressive strength of the first coating 333b is, for example, 1.5 MPa to 10 MPa. The compressive strength is measured in accordance with JIS R2615:1995.

[0040] The top roll 33 includes a first graphite sheet 334 that covers the outer surface of the first insulation material 333. The first graphite sheet 334 has a cylindrical shape. The outer diameter of the first graphite sheet 334 is smaller than the outer diameter of the rotating roll 331, and the outer surface of the first graphite sheet 334 does not come into contact with the upper surface of the glass ribbon GR.

[0041] The first graphite sheet 334 is made of graphite. Graphite has a low coefficient of thermal expansion and high thermal conductivity, and is excellent in thermal shock resistance. By providing the first graphite sheet 334, which has excellent thermal shock resistance, on the outer surface of the first insulation material 333, it is possible to suppress dust falling from the first insulation material 333 onto the glass ribbon GR, thereby reducing the drawbacks of the glass ribbon GR. Furthermore, even if carbon dust adheres to the glass ribbon GR, it will not remain as a defect if it is burned off in the annealing furnace 45.

[0042] Preferably, the first graphite sheet 334 has a cylindrical portion 334a that covers the outer circumferential surface of the first heat-insulating material 333 and a lid portion 334b ​​that covers the end face of the first heat-insulating material 333 opposite to the rotating roll 331. By covering not only the outer circumferential surface of the first heat-insulating material 333 but also the end face of the first heat-insulating material 333 with the first graphite sheet 334, dust generation from the end face of the first heat-insulating material 333 can be suppressed.

[0043] The first graphite sheet 334 does not need to cover the end face of the first insulation material 333 that faces the rotating roll 331. By pressing the end face of the first insulation material 333 against the rotating roll 331, dust generation from the end face of the first insulation material 333 can be suppressed. In addition, by pressing the end face of the first insulation material 333 against the rotating roll 331, the temperature rise of the rotating roll 331 can be suppressed, as will be described later.

[0044] Since the first graphite sheet 334 has a higher thermal conductivity than the first heat-insulating material 333, it is not necessary to cover the end face of the first heat-insulating material 333 that faces the rotating roll 331 in order to suppress the temperature rise of the rotating roll 331. The thermal conductivity of the first graphite sheet 334 in the planar direction is, for example, 100 W / (m·°C) to 800 W / (m·°C) at room temperature, preferably 200 W / (m·°C) to 700 W / (m·°C).

[0045] The thickness t of the first graphite sheet 334 is preferably 0.01 mm to 2.0 mm. If the thickness t of the first graphite sheet 334 is 0.01 mm or more, the durability of the first graphite sheet 334 is good. If the thickness t of the first graphite sheet 334 is 2.0 mm or less, the flexibility of the first graphite sheet 334 is good and the bending process of the cylindrical portion 334a is easy. The thickness t of the first graphite sheet 334 is more preferably 0.02 mm to 1.0 mm, and even more preferably 0.03 mm to 0.5 mm.

[0046] The bulk density of the first graphite sheet 334 is preferably 0.5 g / cm 3 ~1.3 g / cm 3 If the bulk density of the first graphite sheet 334 is 0.5 g / cm 3 or more, the durability of the first graphite sheet 334 is good. If the bulk density of the first graphite sheet 334 is 1.3 g / cm 3 or less, the flexibility of the first graphite sheet 334 is good and the bending process of the cylindrical portion 334a is easy. The bulk density of the first graphite sheet 334 is more preferably 0.7 g / cm 3 ~1.3 g / cm 3 and even more preferably 1.0 g / cm 3 ~1.3 g / cm 3 That is.

[0047] The first heat insulating material 333 has the first film 333b to suppress the dust from falling from the first base material 333a to the glass ribbon GR. However, if the first film 333b is exposed to high temperature for a long time, the first film 333b may crack due to heat. According to the present embodiment, since the first graphite sheet 334 wraps the first film 333b, even if the first film 333b cracks, it is possible to suppress the dust from falling from the first base material 333a to the glass ribbon GR.

[0048] The inventors prepared a first and a second test specimen to confirm the effect of the first graphite sheet 334. The first test specimen consisted of a first heat-insulating material 333, composed of a first base material 333a and a first coating 333b, wrapped in the first graphite sheet 334. The second test specimen consisted only of the first heat-insulating material 333, composed of a first base material 333a and a first coating 333b. The first and second test specimens were subjected to vibration testing after heat treatment. The heat treatment temperature was raised from room temperature to 970°C over 3 hours, then held at 970°C for 2 hours, and then lowered from 970°C to room temperature over 1 hour.

[0049] In the vibration test, the frequency was 20 Hz, the current was 0.5 A, and the test duration was 3 hours. The vibration of the test specimen during the vibration test was stronger than the actual vibration of the top roll 33. After the vibration test, no dust fell from the first test specimen was visible, whereas dust fell from the second test specimen was visible. From these results, it can be seen that the first graphite sheet 334 encases the first coating 333b, which suppresses the falling of dust from the first base material 333a onto the glass ribbon GR even if the first coating 333b cracks.

[0050] As shown in Figure 5, the top roll 33 preferably includes an adhesive layer 335 for bonding the first insulation material 333 and the first graphite sheet 334. In this embodiment, the adhesive layer 335 is provided at intervals along the outer circumference of the first insulation material 333, but it may also be provided over the entire outer circumference of the first insulation material 333. The adhesive layer 335 bonds the outer surface of the first insulation material 333 to the cylindrical portion 334a of the first graphite sheet 334. The adhesive layer 335 can also bond the first graphite sheets 334 to each other. Although not shown, the adhesive layer 335 may also be provided on the end face of the first insulation material 333. The adhesive layer 335 bonds the end face of the first insulation material 333 to the lid portion 334b ​​of the first graphite sheet 334.

[0051] The adhesive layer 335 preferably contains carbon. Carbon has excellent heat resistance and adhesive properties. The adhesive layer 335 can be obtained, for example, by filling a slurry between the outer surface of the first heat-insulating material 333 and the inner surface of the first graphite sheet 334, drying it, and then firing the dried slurry. The firing temperature is preferably higher than the operating temperature of the top roll 33.

[0052] The slurry contains, for example, carbon powder and phenolic resin. The phenolic resin has a high carbon content and a high carbon residue rate after firing. Therefore, an adhesive layer 335 with excellent heat resistance and adhesion can be obtained. The slurry may further contain at least one of an organic solvent and water. It is preferable that the content of the organic solvent and water be as low as possible.

[0053] As shown in Figure 6, it is preferable that the first graphite sheet 334 has a cut 334c at the boundary between the cylindrical portion 334a and the lid portion 334b. The cylindrical portion 334a and the lid portion 334b ​​can be bonded separately to the first insulation material 333, improving assembly workability. The lid portion 334b ​​has, for example, a donut shape. The lid portion 334b ​​may be divided into two parts. This can further improve workability.

[0054] The top roll 33 preferably includes a third graphite sheet 336. The third graphite sheet 336 is provided at the corners of the outer surface and end face of the first insulation material 333, and closes the cut 334c of the first graphite sheet 334. This prevents dust from falling from the cut 334c.

[0055] The third graphite sheet 336 preferably has a cylindrical portion 336a and a lid portion 336b, as shown in Figure 7. The cylindrical portion 336a covers the outer circumferential surface of the first insulation material 333. The lid portion 336b covers the end face of the first insulation material 333 opposite to the rotating roll 331. Unlike the first graphite sheet 334, the third graphite sheet 336 does not have a cut at the boundary between the cylindrical portion 336a and the lid portion 336b.

[0056] As shown in Figure 8, it is preferable that the lid portion 336b has a plurality of notches 336c on the side opposite to the boundary between the lid portion 336b and the cylindrical portion 336a (the boundary shown by the dashed line in Figure 8). Each notch 336c extends to the boundary between the lid portion 336b and the cylindrical portion 336a. By folding the third graphite sheet 336 at that boundary, the lid portion 336b can be formed as shown in Figure 7.

[0057] Unlike the first graphite sheet 334, the third graphite sheet 336 does not have a cut at the boundary between the cylindrical portion 336a and the lid portion 336b. Therefore, it is preferable that the third graphite sheet 336 is thinner than the first graphite sheet 334. The third graphite sheet 336 is easy to fold. It is preferable that the thickness of the third graphite sheet 336 is 1 / 5 or less of the thickness of the first graphite sheet 334.

[0058] If the third graphite sheet 336 is thinner than the first graphite sheet 334, it is preferable to place the third graphite sheet 336 inside the first graphite sheet 334, as shown in Figure 6. This can suppress damage to the third graphite sheet 336 and prevent tearing of the third graphite sheet 336.

[0059] The third graphite sheet 336 is provided inside the first graphite sheet 334 and outside the first insulation material 333. The third graphite sheet 336 also functions as a buffer to prevent the irregularities of the ropes constituting the first insulation material 333 from being transferred to the first graphite sheet 334.

[0060] The third graphite sheet 336 and the first insulation material 333 may be bonded together by an adhesive layer 335, although this is not shown in the diagram. Similarly, the third graphite sheet 336 and the first graphite sheet 334 may also be bonded together by an adhesive layer 335, although this is not shown in the diagram. The third graphite sheet 336 may be provided on the outside of the first graphite sheet 334.

[0061] As shown in Figure 4, the top roll 33 preferably includes a fixed shaft 337. The fixed shaft 337 has a through hole through which the rotating shaft 332 is inserted. The fixed shaft 337 rotatably supports the rotating shaft 332 and reduces vibration of the rotating shaft 332. A sleeve (not shown) to reduce frictional resistance may be provided between the fixed shaft 337 and the rotating shaft 332. The rotating shaft 332 protrudes from the fixed shaft 337, and the first insulation material 333 is provided on the protruding portion. The first insulation material 333 rotates together with the rotating shaft 332. The outer diameter of the fixed shaft 337 is smaller than the outer diameter of the rotating roll 331, and the outer circumference of the fixed shaft 337 does not contact the upper surface of the glass ribbon GR.

[0062] The top roll 33 preferably includes a second heat-insulating material 338 that covers the outer surface of the fixed shaft 337. The outer diameter of the second heat-insulating material 338 is smaller than the outer diameter of the rotating roll 331, and the outer surface of the second heat-insulating material 338 does not come into contact with the upper surface of the glass ribbon GR. The second heat-insulating material 338 restricts heat transfer between the fixed shaft 337 and the glass ribbon GR, suppressing overheating of the fixed shaft 337 and suppressing the cooling and solidification of the glass ribbon GR. The second heat-insulating material 338 is an insulating material. Unlike the first heat-insulating material 333, the second heat-insulating material 338 does not rotate with the rotating shaft 332.

[0063] The second heat-insulating material 338, like the first heat-insulating material 333, preferably has a second base material 338a made of a porous material in order to suppress heat transfer. The second base material 338a is an aggregate of at least one inorganic fiber and inorganic particles. The second base material 338a preferably contains carbon, because even if carbon dust adheres to the glass ribbon GR, it will be burned off in the annealing furnace 45.

[0064] The second base material 338a is formed in a cylindrical shape. A through hole is formed in the center of the second base material 338a. The fixing shaft 337 is inserted through this through hole. Preferably, the second base material 338a covers the outer surface of the fixing shaft 337 over its entire circumference. The second base material 338a has an end face (left face in Figure 4) that faces the end face of the first insulation material 333.

[0065] The second heat-insulating material 338 has, for example, a second base material 338a and a second coating 338b in this order, extending from the radially inner side to the radially outer side of the fixed shaft 337. The second coating 338b is a hardened cement product, similar to the first coating 333b. The second coating 338b covers the outer circumferential surface of the second base material 338a. Preferably, the second coating 338b also covers the end face of the second base material 338a facing the first base material 333a. By wrapping the second base material 338a with the second coating 338b, it is possible to suppress dust falling from the second base material 338a onto the glass ribbon GR, thereby reducing the drawbacks of the glass ribbon GR.

[0066] The top roll 33 preferably includes a second graphite sheet 339 that covers the outer surface of the second heat-insulating material 338. The second graphite sheet 339 has a cylindrical shape. The outer diameter of the second graphite sheet 339 is smaller than the outer diameter of the rotating roll 331, and the outer surface of the second graphite sheet 339 does not come into contact with the upper surface of the glass ribbon GR.

[0067] The second graphite sheet 339 is made of graphite. Graphite has a low coefficient of thermal expansion and high thermal conductivity, and is excellent in thermal shock resistance. By providing the second graphite sheet 339, which has excellent thermal shock resistance, on the outer surface of the second insulation material 338, it is possible to suppress dust falling from the second insulation material 338 onto the glass ribbon GR, thereby reducing the drawbacks of the glass ribbon GR. Furthermore, even if carbon dust adheres to the glass ribbon GR, it will not remain as a defect if it is burned off in the annealing furnace 45.

[0068] Preferably, the second graphite sheet 339 has a cylindrical portion 339a that covers the outer circumferential surface of the second heat-insulating material 338 and a lid portion 339b that covers the end face of the second heat-insulating material 338 facing the first heat-insulating material 333. By covering not only the outer circumferential surface of the second heat-insulating material 338 but also the end face of the second heat-insulating material 338 with the second graphite sheet 339, dust generation from the end face of the second heat-insulating material 338 can be suppressed.

[0069] The second heat-insulating material 338 has a second coating 338b, which suppresses dust from falling from the second base material 338a onto the glass ribbon GR. However, if the second coating 338b is exposed to high temperatures for a long period of time, the second coating 338b may crack due to the heat. According to this embodiment, the second graphite sheet 339 wraps around the second coating 338b, so even if the second coating 338b cracks, dust from falling from the second base material 338a onto the glass ribbon GR can be suppressed.

[0070] The thickness, thermal conductivity, and bulk density of the second graphite sheet 339 are the same as those of the first graphite sheet 334.

[0071] Although not shown in the figures, the top roll 33 preferably includes an adhesive layer for bonding the second insulation material 338 and the second graphite sheet 339. The adhesive layer is provided at intervals along the outer circumference of the second insulation material 338, but may also be provided over the entire outer circumference of the second insulation material 338. The adhesive layer bonds the outer surface of the second insulation material 338 to the cylindrical portion 339a of the second graphite sheet 339. The adhesive layer can also bond the second graphite sheets 339 to each other. The adhesive layer may also be provided on the end face of the second insulation material 338, or it may bond the end face of the second insulation material 338 to the lid portion 339b of the second graphite sheet 339. The adhesive layer preferably contains carbon.

[0072] Although not shown in the figures, it is preferable that the second graphite sheet 339 has a cut at the boundary between the cylindrical portion 339a and the lid portion 339b. The cylindrical portion 339a and the lid portion 339b can be bonded separately to the second insulation material 338, improving assembly workability. The lid portion 339b has, for example, a donut shape. The lid portion 339b may be divided into two parts. This can further improve workability.

[0073] Although not shown in the diagram, the top roll 33 preferably includes a fourth graphite sheet. The fourth graphite sheet is provided at the corners of the outer surface and end face of the second insulation material 338, sealing the gap in the second graphite sheet 339. This prevents dust from falling through the gap.

[0074] The fourth graphite sheet preferably has a cylindrical portion that covers the outer circumferential surface of the second insulation material 338 and a lid portion that covers the end face of the second insulation material 338 facing the first insulation material 333. Unlike the second graphite sheet 339, the fourth graphite sheet does not have a cut at the boundary between the cylindrical portion and the lid portion. The lid portion of the fourth graphite sheet is formed in the same way as the lid portion 336b of the third graphite sheet 336.

[0075] Unlike the second graphite sheet 339, the fourth graphite sheet does not have a cut at the boundary between the cylindrical portion and the lid portion. Therefore, it is preferable that the fourth graphite sheet is thinner than the second graphite sheet 339. The fourth graphite sheet is easy to fold. It is preferable that the thickness of the fourth graphite sheet is 1 / 5 or less of the thickness of the second graphite sheet 339.

[0076] If the fourth graphite sheet is thinner than the second graphite sheet 339, it is preferable to place the fourth graphite sheet inside the second graphite sheet 339. This can suppress damage to the fourth graphite sheet and prevent it from tearing.

[0077] The fourth graphite sheet is provided inside the second graphite sheet 339 and outside the second insulation material 338. The fourth graphite sheet also functions as a buffer to prevent the irregularities of the ropes constituting the second insulation material 338 from being transferred to the second graphite sheet 339.

[0078] The following additional information is disclosed regarding the above embodiments, etc.

[0079] [Note 1] A top roll supporting a glass ribbon, A rotating roll in contact with the upper surface of the glass ribbon, A rotating shaft that rotates the aforementioned rotating roll, A first heat-insulating material covering the outer surface of the rotating shaft, A first graphite sheet covering the outer surface of the first insulation material, A top roll equipped with this feature.

[0080] [Note 2] The top roll according to Appendix 1, wherein the first heat-insulating material comprises, in this order, a first matrix material which is an aggregate of inorganic fibers and inorganic particles, and a first coating which is a hardened cement, from the radially inner side to the radially outer side of the rotating shaft.

[0081] [Note 3] The first insulation material and the first graphite sheet are bonded together by an adhesive layer, The adhesive layer is a top roll as described in Appendix 1 or 2, containing carbon.

[0082] [Note 4] The top roll according to any one of the appendices 1 to 3, wherein the first graphite sheet has a cylindrical portion that covers the outer surface of the first insulation material and a lid portion that covers the end face of the first insulation material opposite to the rotating roll.

[0083] [Note 5] The first graphite sheet has a cut at the boundary between the cylindrical portion and the lid portion. The top roll as described in Appendix 4, further comprising a third graphite sheet that seals the cut in the first graphite sheet.

[0084] [Note 6] The third graphite sheet is thinner than the first graphite sheet and is provided inside the first graphite sheet, as described in Appendix 5.

[0085] [Note 7] A fixed shaft having a through hole through which the aforementioned rotating shaft is inserted, A second heat-insulating material covering the outer surface of the fixed shaft, A second graphite sheet covering the outer surface of the second insulation material, A top roll equipped with any one of the features described in Appendix 1 to 6.

[0086] [Note 8] The top roll described in one of the notes 1-7, A bathtub containing molten metal in contact with the lower surface of the glass ribbon, A glass plate manufacturing apparatus equipped with the following features.

[0087] [Note 9] A method for manufacturing a glass plate, comprising forming the glass ribbon on the liquid surface of molten metal using a top roll described in any one of the appendices 1 to 7.

[0088] The top roll, glass plate manufacturing apparatus, and glass plate manufacturing method relating to this disclosure have been described above, but this disclosure is not limited to the embodiments described above. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These also naturally fall within the technical scope of this disclosure. [Explanation of Symbols]

[0089] 1. Glass plate manufacturing apparatus 3 Molding equipment 33 Top Roll 331 Rotating Roll 332 Rotation axis 333 1st insulation material 333a 1st base material 333b First coating 334 1st Graphite Sheet 335 Adhesive layer 336 Third Graphite Sheet 337 Fixed axis 338 Second insulation material 339 Second Graphite Sheet GR Glass Ribbon

Claims

1. A top roll supporting a glass ribbon, A rotating roll in contact with the upper surface of the glass ribbon, A rotating shaft that rotates the aforementioned rotating roll, A first heat-insulating material covering the outer surface of the rotating shaft, A first graphite sheet covering the outer surface of the first heat-insulating material, A top roll equipped with this feature.

2. The top roll according to claim 1, wherein the first heat-insulating material comprises, in this order, a first base material which is an aggregate of inorganic fibers and inorganic particles, and a first coating which is a hardened cement, from the radially inner side to the radially outer side of the rotating shaft.

3. The first insulation material and the first graphite sheet are bonded together by an adhesive layer, The top roll according to claim 1 or 2, wherein the adhesive layer contains carbon.

4. The top roll according to claim 1 or 2, wherein the first graphite sheet has a cylindrical portion that covers the outer surface of the first heat-insulating material and a lid portion that covers the end face of the first heat-insulating material opposite to the rotating roll.

5. The first graphite sheet has a cut at the boundary between the cylindrical portion and the lid portion. The top roll according to claim 4, further comprising a third graphite sheet that seals the cut in the first graphite sheet.

6. The top roll according to claim 5, wherein the third graphite sheet is thinner than the first graphite sheet and is provided inside the first graphite sheet.

7. A fixed shaft having a through hole through which the aforementioned rotating shaft is inserted, A second heat-insulating material covers the outer surface of the aforementioned fixed shaft, A second graphite sheet covering the outer surface of the second insulation material, The top roll according to claim 1 or 2, comprising:

8. The top roll according to claim 1 or 2, A bathtub containing molten metal in contact with the lower surface of the glass ribbon, A glass plate manufacturing apparatus equipped with the following features.

9. A method for manufacturing a glass plate, comprising forming the glass ribbon on the liquid surface of molten metal using the top roll described in claim 1 or 2.

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