JP2015151282A - Float glass manufacturing apparatus and float glass manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a float glass manufacturing apparatus and a float glass manufacturing method that can suppress a local decrease of the width-directional temperature distribution of a glass ribbon between a molding device and a slow cooling device.SOLUTION: A float glass manufacturing apparatus includes a temperature adjusting device which adjusts the temperature of a glass ribbon G between a molding device and a slow cooling device, and the temperature adjusting device has a plurality of heater groups 51, 52 comprising a plurality of heaters 51a to 51g, 52a to 52g arranged along a width of the glass ribbon G. The heaters 51a to 51g, 52a to 52g in the heater groups 51, 52 are controlled by zones Z11 to Z17, Z21 to Z27 arrayed along the width of the glass ribbon G, and the heater groups 51, 52 are arranged on opposite sides across the glass ribbon G, mutual borders of the upper-side zones Z11 to Z17 and mutual borders of the lower-side zones Z21 to Z27 being shifted at at least one place along the width of the glass ribbon G.

Description

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

  The float glass manufacturing apparatus includes a molding apparatus for forming a plate-shaped glass ribbon on molten metal in a bathtub, a slow cooling apparatus for gradually cooling the glass ribbon, and a temperature of the glass ribbon between the molding apparatus and the slow cooling apparatus. And a temperature adjusting device for adjusting (see, for example, Patent Document 1).

  The temperature adjusting device has a plurality of heater groups including a plurality of heaters arranged in the width direction of the glass ribbon in order to adjust the temperature distribution in the width direction of the glass ribbon. Each heater group is controlled for each zone arranged in the width direction of the glass ribbon.

Japanese Patent No. 3217176

  Between the forming device and the slow cooling device, the temperature of the glass ribbon is near the transition point. In general, the linear expansion coefficient of glass changes greatly at the transition point of glass.

  There is no heater at the boundary between zones arranged in the width direction of the glass ribbon, and the temperature distribution in the width direction of the glass ribbon may be locally reduced, which may cause unintended deformation. Examples of unintentional deformation include cracks, wrinkles, swells, and warps. Moreover, a large residual strain (stress) may remain in the glass ribbon due to a local decrease in the temperature distribution in the width direction of the glass ribbon.

  This invention is made in view of the said subject, Comprising: The provision of the float glass manufacturing apparatus which can suppress the local fall of the temperature distribution of the width direction of the glass ribbon between a shaping | molding apparatus and a slow cooling apparatus is provided. Main purpose.

In order to solve the above problems, according to one aspect of the present invention,
A molding apparatus for molding a plate-shaped glass ribbon on the molten metal in the bathtub;
A slow cooling device for slowly cooling the glass ribbon;
A temperature adjusting device for adjusting the temperature of the glass ribbon between the forming device and the slow cooling device;
The temperature adjusting device has a plurality of heater groups composed of a plurality of heaters arranged in the width direction of the glass ribbon,
Each of the heater groups is controlled for each zone arranged in the width direction of the glass ribbon,
Two heater groups of the plurality of heater groups are disposed on opposite sides of the glass ribbon, are disposed at the same position in the conveyance direction of the glass ribbon, and the upper boundary of the zone and the lower side There is provided a float glass manufacturing apparatus which is disposed so as to be shifted in the width direction of the glass ribbon at least at one place from the boundary of the zone.

  According to one aspect of the present invention, there is provided a float glass manufacturing apparatus that can suppress a local decrease in the temperature distribution in the width direction of the glass ribbon between the forming apparatus and the slow cooling apparatus.

It is a figure which shows the float glass manufacturing apparatus by one Embodiment of this invention. It is a figure which shows the positional relationship of two heater groups arrange | positioned on the opposite side on both sides of the glass ribbon of FIG. It is a figure which shows the positional relationship of the two heater groups arrange | positioned at intervals in the conveyance direction of the glass ribbon of FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted. In the following description, “˜” representing a numerical range means a range including numerical values before and after that.

  FIG. 1 is a view showing a float glass manufacturing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the float glass manufacturing apparatus includes a forming apparatus 10, a slow cooling apparatus 20, and a temperature adjusting apparatus 30.

  The forming apparatus 10 forms a plate-like glass ribbon G on the molten metal M in the bathtub 11. The glass ribbon G gradually hardens while flowing on the molten metal M. The glass ribbon G is pulled up from the molten metal M in the downstream region of the bathtub 11 and sent toward the slow cooling device 20. The molding apparatus 10 includes a bathtub 11, a roof 15, a heater 16, and the like.

  The bathtub 11 accommodates the molten metal M. The molten metal M may be a common one, and may be, for example, molten tin or a molten tin alloy. The bathtub 11 is composed of, for example, a metal casing 12 and a brick layer 13.

  The metal casing 12 suppresses mixing of outside air into the bathtub 11. The metal casing 12 is formed by welding a plurality of metal plates, for example.

  The brick layer 13 covers the inner surface of the metal casing 12. The brick layer 13 may be an assembly in which a plurality of bricks are assembled in a box shape, and contains the molten metal M therein.

  The roof 15 is disposed above the bathtub 11 and covers the upper space of the bathtub 11. In the upper space of the bathtub 11, reducing gas or the like is supplied from the through hole 15 a of the roof 15 in order to prevent the molten metal M from being oxidized. As the reducing gas, for example, a mixed gas of nitrogen gas and hydrogen gas is used. The upper space of the bathtub 11 is set to a positive pressure higher than the atmospheric pressure in order to prevent outside air from being mixed.

  The heater 16 is inserted into the through hole 15a of the roof 15, protrudes downward from the roof 15, and heats the glass ribbon G and the like. The heater 16 may be a general one, for example, a SiC heater.

  A plurality of heaters 16 are arranged at intervals in the width direction of the glass ribbon G (the direction perpendicular to the paper surface in FIG. 1) and the flow direction of the glass ribbon G (the left-right direction in FIG. 1).

  The slow cooling device 20 cools the glass ribbon G slowly. The slow cooling device 20 includes a slow cooling furnace 21, a transport roll 22, and the like. The transport roll 22 is rotatable about its center line, is driven to rotate by a motor or the like, and transports the glass ribbon G horizontally in the slow cooling furnace 21. The glass ribbon G is gradually cooled while being conveyed. The glass ribbon G has a flat part between both side edge parts. Since both side edges of the glass ribbon G are thicker than the flat part of the glass ribbon G, they are cut off after slow cooling. Thereby, the float glass of substantially uniform board thickness is obtained.

  The temperature adjusting device 30 adjusts the temperature of the glass ribbon G between the forming device 10 and the slow cooling device 20. The temperature adjusting device 30 limits the temperature drop of the glass ribbon G that is away from the molten metal M. Since the molten metal M stores heat, the glass ribbon G is difficult to cool while being in contact with the molten metal M, but is likely to be cooled away from the molten metal M. Between the shaping | molding apparatus 10 and the slow cooling apparatus 20, the temperature difference (absolute value) of the atmosphere near each side edge part of the glass ribbon G and the atmosphere near a flat part may be 20 degrees C or less, for example.

  The temperature adjustment device 30 includes a dross box 31, a sealing 32, a lift-out roll 33, a drape 34, a seal block 35, heater groups 51 to 54, temperature sensors 61 to 62, and a control device 70.

  The dross box 31 is disposed below the glass ribbon G, and collects molten metal M adhering to the bottom surface of the glass ribbon G (called dross). The inner surface of the dross box 31 is covered with a heat insulating material 41, and heat radiation from the dross box 31 to the outside is limited.

  The sealing 32 is disposed above the glass ribbon G. The upper surface of the ceiling 32 is covered with a heat insulating material 42, and heat radiation from the ceiling 32 to the outside is limited.

  The lift-out roll 33 pulls up the glass ribbon G from the molten metal M and conveys it toward the slow cooling device 20. The lift-out roll 33 is rotatable around its center line and is driven to rotate by a motor or the like.

  The drape 34 is suspended from the ceiling 32 and blocks the gas flow above the glass ribbon G. Thereby, mixing of the hydrogen gas from the shaping | molding apparatus 10 can be suppressed, and the temperature fluctuation by combustion of hydrogen gas can be suppressed. The drape 34 is provided above the lift-out roll 33.

  The seal block 35 is in contact with the lift-out roll 33, thereby blocking the gas flow below the glass ribbon G, and scraping off the dross attached to the lift-out roll 33. The dross is collected in the dross box 31. The seal block 35 is made of carbon, for example.

  The heater group 51 heats the glass ribbon G from above as shown in FIG. The heater group 51 includes a plurality of heaters 51a to 51g (see FIGS. 2 and 3) arranged in the width direction of the glass ribbon G. The region where the heater group 51 is provided is composed of a plurality of zones Z11 to Z17 (see FIGS. 2 and 3) arranged in the width direction of the glass ribbon G. The plurality of heaters 51a to 51g are controlled independently for each of the zones Z11 to Z17.

  As shown in FIG. 1, the heater group 52 is disposed at the same position in the conveyance direction of the glass ribbon G with respect to the heater group 51, and heats the glass ribbon G from below. The heater group 52 includes a plurality of heaters 52a to 52g (see FIG. 2) arranged in the width direction of the glass ribbon G. The region where the heater group 52 is provided includes a plurality of zones Z21 to Z27 (see FIG. 2) arranged in the width direction of the glass ribbon G. The plurality of heaters 52a to 52g are independently controlled for each of the zones Z21 to Z27.

  As shown in FIG. 1, the heater group 53 is disposed at an interval in the conveyance direction of the glass ribbon G with respect to the heater group 51, and heats the glass ribbon G from above. The heater group 53 includes a plurality of heaters 53a to 53g (see FIG. 3) arranged in the width direction of the glass ribbon G. The region in which the heater group 53 is provided includes a plurality of zones Z31 to Z37 (see FIG. 3) arranged in the width direction of the glass ribbon G. The plurality of heaters 53a to 53g are controlled independently for each of the zones Z31 to Z37.

  As shown in FIG. 1, the heater group 54 is disposed at the same position in the conveyance direction of the glass ribbon G with respect to the heater group 53, and heats the glass ribbon G from below. The heater group 54 includes a plurality of heaters arranged in the width direction of the glass ribbon G. The region where the heater group 54 is provided is composed of a plurality of zones arranged in the width direction of the glass ribbon G. The plurality of heaters are controlled independently for each zone.

  In the present embodiment, the number of zones is the same among the plurality of heater groups, but may be different. For example, the number of zones may be different between the heater group 51 and the heater group 52 disposed at the same position in the conveyance direction of the glass ribbon G. Further, the number of zones may be different between the heater group 51 and the heater group 53 arranged at intervals in the conveyance direction of the glass ribbon G.

  In this embodiment, in each heater group, the number of zones is the same as the number of heaters, but the number of zones may be smaller than the number of heaters. A plurality of heaters may be disposed in one zone.

  FIG. 2 is a diagram showing a positional relationship between two heater groups arranged on the opposite side across the glass ribbon of FIG. In FIG. 2, the width direction of the glass ribbon is the left-right direction, and the conveyance direction of the glass ribbon is a direction perpendicular to the paper surface. In FIG. 2, a broken line indicates an extension of the boundary between the upper zones.

  As shown in FIG. 2, the two heater groups 51 and 52 among the plurality of heater groups 51 to 54 are arranged on the opposite side across the glass ribbon G, and are arranged at the same position in the conveyance direction of the glass ribbon G. Established. The two heater groups 51 and 52 are arranged in the width direction of the glass ribbon G at at least one location (all locations in the present embodiment) between the upper zones Z11 to Z17 and the lower zones Z21 to Z27. They are arranged in a shifted manner. The region without the upper heater and the region without the lower heater are shifted in the width direction of the glass ribbon G at least at one location. Therefore, the local fall of the width direction temperature distribution of the glass ribbon G can be suppressed. As a result, unintended deformation of the glass ribbon G can be suppressed. Further, the residual strain (stress) of the glass ribbon G can be reduced. The upper heater group 51 and the lower heater group 52 may be controlled independently.

  Similarly, the remaining two heater groups 53 and 54 among the plurality of heater groups 51 to 54 are disposed on the opposite side with the glass ribbon G interposed therebetween, and are disposed at the same position in the conveyance direction of the glass ribbon G. The The two heater groups 53 and 54 are arranged by shifting the boundary of the upper zones Z31 to Z37 and the boundary of the lower zone in the width direction of the glass ribbon G at at least one location (all locations in this embodiment). May be provided. The upper heater group 53 and the lower heater group 54 may be controlled independently.

  FIG. 3 is a diagram showing a positional relationship between two heater groups arranged at intervals in the conveyance direction of the glass ribbon of FIG. In FIG. 3, the width direction of a glass ribbon is an up-down direction, and the conveyance direction of a glass ribbon is a left-right direction. In FIG. 3, a broken line indicates an extension of the boundary between zones on the upstream side in the transport direction.

  As shown in FIG. 3, the two heater groups 51 and 53 among the plurality of heater groups 51 to 54 are disposed above the glass ribbon G, and are disposed at intervals in the conveyance direction of the glass ribbon G. Is done. The two heater groups 51 and 53 have a glass ribbon at least at one location (all locations in the present embodiment) at the boundary between the zones Z11 to Z17 on the upstream side in the transport direction and the boundary between the zones Z31 to Z37 on the downstream side in the transport direction. It may be arranged shifted in the width direction of G. The region without the heater on the upstream side in the transport direction and the region without the heater on the downstream side in the transport direction are shifted in the width direction of the glass ribbon G at least at one location. Therefore, the local fall of the width direction temperature distribution of the glass ribbon G can be suppressed. As a result, unintended deformation of the glass ribbon G can be suppressed. Moreover, the residual distortion of the glass ribbon G can be reduced. The heater group 51 on the upstream side in the transport direction and the heater group 53 on the downstream side in the transport direction may be controlled independently. The temperature gradient in the conveyance direction of the glass ribbon G can be adjusted.

  Similarly, the remaining two heater groups 52 and 54 among the plurality of heater groups 51 to 54 are disposed below the glass ribbon G, and are disposed at intervals in the conveyance direction of the glass ribbon G. . The two heater groups 52 and 54 have the width of the glass ribbon G at at least one location (all locations in the present embodiment) at the boundary between the zones Z21 to Z27 on the upstream side in the transport direction and the boundary between the zones on the downstream side in the transport direction. It may be arranged shifted in the direction. The heater group 52 on the upstream side in the transport direction and the heater group 54 on the downstream side in the transport direction may be controlled independently. The temperature gradient in the conveyance direction of the glass ribbon G can be adjusted.

  In the present embodiment, the number of heater groups arranged at intervals in the conveyance direction of the glass ribbon G is two, but may be three or more. In this case, any two heater groups are disposed by shifting the boundary between the zones on the upstream side in the transport direction and the boundary between the zones on the downstream side in the transport direction in at least one place in the width direction of the glass ribbon G. Good. There may be another heater group between any two heater groups.

  The distance in the width direction of the glass ribbon G between the boundary between the zones of the heater groups 51 to 54 and the boundary Ga between the flat portion and the side edge of the glass ribbon G is, for example, 25 mm or more, preferably 50 mm or more, more preferably. May be 100 mm or more. Since the temperature of the boundary Ga between the flat portion and the side edge portion of the glass ribbon G can be controlled, the residual strain due to the thickness change at the boundary Ga can be reduced.

  The temperature sensors 61 and 62 (see FIG. 1) are composed of a thermocouple or a radiation thermometer. The temperature sensors 61 and 62 measure the ambient temperature around the glass ribbon G or the temperature of the glass ribbon G itself. Since there is almost no temperature gradient in the thickness direction of the glass ribbon G, the temperature sensors 61 and 62 may be disposed on one side (the upper side in FIG. 1) of the glass ribbon G. In this case, the number of temperature sensors is less than the number of zones. The temperature sensor may be disposed on both sides of the glass ribbon G. Further, the number of temperature sensors may be the same as the number of zones or may be larger than the number of zones.

  The control device 70 includes a storage unit such as a memory and a CPU, and controls the heater groups 51 to 54 by causing the CPU to execute a control program stored in the storage unit. The control apparatus 70 controls each heater group 51-54 independently for every zone.

  For example, the control device 70 may control each heater based on the measured temperature of the temperature sensors 61 and 62 and the set temperature. At this time, the control device 70 may calculate the temperature at a predetermined location from the measurement positions and measurement temperatures of the plurality of temperature sensors. The control device 70 may control each heater so that the deviation between the measured temperature or calculated temperature and the set temperature becomes zero.

  In the present embodiment, each heater is automatically controlled by the control device 70, but may be manually controlled.

  Next, with reference to FIG. 1 again, a float glass manufacturing method using the float glass manufacturing apparatus having the above-described configuration will be described.

  The float glass manufacturing method includes a forming step of forming a plate-like glass ribbon G on the molten metal M in the bathtub 11 and a slow cooling step of gradually cooling the glass ribbon G. The glass ribbon G gradually hardens while flowing on the molten metal M. The glass ribbon G is pulled up from the molten metal M in the downstream area of the bathtub 11 and is conveyed toward the slow cooling furnace 21 on the lift-out roll 33. Thereafter, the glass ribbon G is gradually cooled while being transported on the transport roll 22 in the slow cooling furnace 21. The glass ribbon G has a flat part between both side edge parts. Since both side edges of the glass ribbon G are thicker than the flat part of the glass ribbon G, they are cut off after slow cooling. Thereby, the float glass of substantially uniform board thickness is obtained.

  The temperature (° C.) of the glass ribbon G is, for example, Tg + 80 to Tg, preferably Tg + 50 to Tg + 15, more preferably Tg + 30 to Tg + 15 at the outlet of the molding apparatus 10. Here, “Tg” means a glass transition temperature.

  Further, the temperature (° C.) of the glass ribbon G is, for example, Tg + 30 to Tg-50, preferably Tg + 15 to Tg-50, and more preferably Tg + 15 to Tg-35 at the inlet of the slow cooling device 20.

  Between the shaping | molding apparatus 10 and the slow cooling apparatus 20, the temperature of the glass ribbon G is the temperature of a transition point vicinity. In general, the linear expansion coefficient of glass changes greatly at the transition point of glass.

  The float glass manufacturing method includes a temperature adjustment step of adjusting the temperature of the glass ribbon G between the forming apparatus 10 and the slow cooling apparatus 20. In the temperature adjustment step, a plurality of heater groups including a plurality of heaters arranged in the width direction of the glass ribbon G are used. The arrangement and control of the heater groups 51 to 54 and their effects are as described above.

  The plate | board thickness of the float glass manufactured is 0.7 mm or less, for example, Preferably it is 0.5 mm or less, More preferably, it is 0.3 mm or less.

  The manufactured float glass is used as, for example, a glass substrate for display, a cover glass for display, and a window glass.

The float glass produced may be alkali-free glass when used as a glass substrate for a display. The alkali-free glass is a glass that does not substantially contain an alkali metal oxide such as Na ₂ O, K ₂ O, or Li ₂ O. The alkali-free glass may have a total content of alkali metal oxides of 0.1% by mass or less.

Alkali-free glass, for example, represented by mass% based on _{oxide, SiO 2: 50% ~73%} , Al 2 O 3: 10.5% ~24%, B 2 O 3: 0% ~12%, MgO : 0% to 10%, CaO: 0% to 14.5%, SrO: 0% to 24%, BaO: 0% to 13.5%, MgO + CaO + SrO + BaO: 8% to 29.5%, ZrO ₂ : 0% Contains ~ 5%.

When the alkali-free glass has both a high strain point and high solubility, it is preferably expressed in terms of mass% on the basis of oxide, SiO ₂ : 58% to 66%, Al ₂ O ₃ : 15% to 22%, B ₂ O ₃ : 5% to 12%, MgO: 0% to 8%, CaO: 0% to 9%, SrO: 3% to 12.5%, BaO: 0% to 2%, MgO + CaO + SrO + BaO: 9% to Contains 18%.

When it is desired to obtain a particularly high strain point, the alkali-free glass is preferably expressed by mass% based on oxide, SiO ₂ : 54% to 73%, Al ₂ O ₃ : 10.5% to 22.5%, _{B 2 O 3: 0% ~5.5} %, MgO: 0% ~10%, CaO: 0% ~9%, SrO: 0% ~16%, BaO: 0% ~2.5%, MgO + CaO + SrO + BaO: 8 % To 26%.

  The float glass produced may be a chemically strengthened glass when used as a cover glass for a display. What chemically-strengthened the glass for chemical strengthening is used as a cover glass. In the chemical strengthening treatment, ions having a small ion radius (for example, Li ions or Na ions) among alkali ions contained on the glass surface are replaced with ions having a large ion radius (for example, K ions) to obtain a predetermined depth from the glass surface. A compressive stress layer is formed.

Chemically strengthened glass, for example as represented by mol% based on _{oxides, SiO 2: 62% ~68%} , Al 2 O 3: 6% ~12%, MgO: 7% ~13%, Na 2 O: 9% to _17%, K 2 O: containing 0% to 7%, the difference obtained by subtracting the content of _Al 2 _{O 3} from the total content of Na ₂ O and _{K 2} O is less than 10%, a ZrO ₂ When it contains, the content is 0.8% or less.

Another chemically strengthened glass is represented by mol% based on _{oxides, SiO 2: 65% ~85%} , Al 2 O 3: 3% ~15%, Na 2 O: 5% ~15%, K 2 O : 0% to less than 2%, MgO: 0% to 15%, ZrO ₂ : 0% to 1%, the total content of SiO ₂ and Al ₂ O ₃ SiO ₂ + Al ₂ O ₃ is 88% or less It is.

The float glass produced may be soda lime glass when used as a window glass. Soda lime glass, for example, represented by mass% based on _{oxide, SiO 2: 65% ~75%} , Al 2 O 3: 0% ~3%, CaO: 5% ~15%, MgO: 0% ~15% , Na ₂ O: 10% to 20%, K ₂ O: 0% to 3%, Li ₂ O: 0% to 5%, Fe ₂ O ₃ : 0% to 3%, TiO ₂ : 0% to 5% CeO ₂ : 0% to 3%, BaO: 0% to 5%, SrO: 0% to 5%, B ₂ O ₃ : 0% to 5%, ZnO: 0% to 5%, ZrO ₂ : 0% _{~5%, SnO 2: 0%} ~3%, SO 3: contains 0% to 0.5%.

  As mentioned above, although embodiment of float glass manufacturing apparatus etc. was described, this invention is not limited to the said embodiment etc., In the range of the summary of this invention described in the claim, various deformation | transformation and improvement are possible. Is possible.

DESCRIPTION OF SYMBOLS 10 Molding apparatus 11 Bath 12 Metal casing 13 Brick layer 20 Slow cooling apparatus 30 Temperature control apparatus 31 Dross box 32 Sealing 33 Lift-out rolls 51-54 Heater group G Glass ribbon M Molten metal

Claims (13)

A molding apparatus for molding a plate-shaped glass ribbon on the molten metal in the bathtub;
A slow cooling device for slowly cooling the glass ribbon;
A temperature adjusting device for adjusting the temperature of the glass ribbon between the forming device and the slow cooling device;
The temperature adjusting device has a plurality of heater groups composed of a plurality of heaters arranged in the width direction of the glass ribbon,
The plurality of heaters of each of the heater groups is controlled for each zone arranged in the width direction of the glass ribbon,
Two heater groups of the plurality of heater groups are arranged on the opposite side across the glass ribbon, are arranged at the same position in the conveying direction of the glass ribbon, and the upper and lower boundaries between the zones are below The float glass manufacturing apparatus arrange | positioned by shifting in the width direction of the said glass ribbon in the width direction of the said glass ribbon in at least one place with the boundary of the said zone of the side.   Two heater groups of the plurality of heater groups are arranged at intervals in the conveyance direction of the glass ribbon, and a boundary between the zones on the upstream side in the conveyance direction and a boundary between the zones on the downstream side in the conveyance direction The float glass manufacturing apparatus according to claim 1, wherein the at least one location is shifted in the width direction of the glass ribbon.   3. The float glass manufacturing apparatus according to claim 1, wherein two heater groups of the plurality of heater groups are arranged at intervals in the conveyance direction of the glass ribbon and are independently controlled. The temperature adjusting device is:
A temperature sensor;
The float glass manufacturing apparatus of any one of Claims 1-3 which has a control apparatus which controls the said heater based on the measured temperature of this temperature sensor, and preset temperature. Having a temperature adjustment step of adjusting the temperature of the glass ribbon between the molding device and the slow cooling device,
In the temperature adjustment step, a plurality of heater groups including a plurality of heaters arranged in the width direction of the glass ribbon are used,
The plurality of heaters of each of the heater groups is controlled for each zone arranged in the width direction of the glass ribbon,
Two heater groups of the plurality of heater groups are arranged on the opposite side across the glass ribbon, are arranged at the same position in the conveying direction of the glass ribbon, and the upper and lower boundaries between the zones are below The float glass manufacturing method arrange | positioned by shifting in the width direction of the said glass ribbon in the width direction of the said glass ribbon in the at least 1 place with the boundary of the said zone of the side.   Two heater groups of the plurality of heater groups are arranged at intervals in the conveyance direction of the glass ribbon, and a boundary between the zones on the upstream side in the conveyance direction and a boundary between the zones on the downstream side in the conveyance direction The float glass manufacturing method according to claim 5, wherein the at least one location is shifted in the width direction of the glass ribbon.   The float glass manufacturing method according to claim 5 or 6, wherein two heater groups among the plurality of heater groups are arranged at intervals in the conveyance direction of the glass ribbon and are independently controlled.   The float glass manufacturing method according to any one of claims 5 to 7, wherein in the temperature adjustment step, the heater is automatically controlled based on a temperature measured by a temperature sensor and a set temperature.   The float glass manufacturing method according to any one of claims 5 to 8, wherein the manufactured float glass is alkali-free glass. The alkali-free glass is represented by mass% based on _{oxide, SiO 2: 50% ~73%} , Al 2 O 3: 10.5% ~24%, B 2 O 3: 0% ~12%, MgO: 0% to 10%, CaO: 0% to 14.5%, SrO: 0% to 24%, BaO: 0% to 13.5%, MgO + CaO + SrO + BaO: 8% to 29.5%, ZrO ₂ : 0% to The float glass manufacturing method of Claim 9 containing 5%.   The float glass manufacturing method according to any one of claims 5 to 8, wherein the manufactured float glass is a glass for chemical strengthening. The chemically strengthened glass is represented by mol% based on _{oxides, SiO 2: 62% ~68%} , Al 2 O 3: 6% ~12%, MgO: 7% ~13%, Na 2 O: 9% to _17%, K 2 O: containing 0% to 7%, the difference obtained by subtracting the content of _Al 2 _{O 3} from the total content of Na ₂ O and _{K 2} O is less than 10%, a ZrO ₂ The float glass manufacturing method of Claim 11 whose content is 0.8% or less when it contains. The chemically strengthened glass is represented by mol% based on _{oxides, SiO 2: 65% ~85%} , Al 2 O 3: 3% ~15%, Na 2 O: 5% ~15%, K 2 O: 0% to less than 2%, MgO: 0% to 15%, ZrO ₂ : 0% to 1%, and the total content of SiO ₂ and Al ₂ O ₃ is SiO ₂ + Al ₂ O ₃ is 88% or less The method for producing float glass according to claim 11.

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