WO2015033931A1 - Manufacturing method for molten glass and manufacturing method for sheet glass using same - Google Patents

Manufacturing method for molten glass and manufacturing method for sheet glass using same Download PDF

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Publication number
WO2015033931A1
WO2015033931A1 PCT/JP2014/073071 JP2014073071W WO2015033931A1 WO 2015033931 A1 WO2015033931 A1 WO 2015033931A1 JP 2014073071 W JP2014073071 W JP 2014073071W WO 2015033931 A1 WO2015033931 A1 WO 2015033931A1
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Prior art keywords
molten glass
flow
downstream
bubbler
melting tank
Prior art date
Application number
PCT/JP2014/073071
Other languages
French (fr)
Japanese (ja)
Inventor
亮介 赤木
信 楜澤
豊作 米津
信 吉川
智之 井出
Original Assignee
旭硝子株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by 旭硝子株式会社 filed Critical 旭硝子株式会社
Priority to CN201480049184.9A priority Critical patent/CN105517963B/en
Priority to KR1020167005406A priority patent/KR102196157B1/en
Priority to JP2015535481A priority patent/JP6304256B2/en
Publication of WO2015033931A1 publication Critical patent/WO2015033931A1/en

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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/18—Stirring devices; Homogenisation
    • C03B5/193—Stirring devices; Homogenisation using gas, e.g. bubblers
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/18—Stirring devices; Homogenisation
    • C03B5/183—Stirring devices; Homogenisation using thermal means, e.g. for creating convection currents
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C03B5/235—Heating the glass
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
    • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
    • C03C3/093—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium containing zinc or zirconium

Definitions

  • the present invention relates to a molten glass production method and a plate glass production method using the same. More specifically, the present invention relates to a molten glass manufacturing method for producing high-quality non-alkali glass with high homogeneity and a manufacturing method of plate glass using the same.
  • alkali-free glass that does not substantially contain alkali metal ions in order to increase the insulating properties of the glass substrate.
  • alkali-free glass is preferable for the production of a glass substrate for FPD because it has a small coefficient of thermal expansion.
  • the melting furnace described in Patent Document 1 the melting furnace is divided into an upstream zone and a downstream zone by crossing sill, and a molten glass circulation flow (upstream circulation flow, downstream circulation flow) is formed in each zone. , Melting raw materials and homogenizing molten glass. More specifically, the glass raw material is melted by forming an upstream circulation flow in the upstream zone, and the molten glass is homogenized by forming a downstream circulation flow in the downstream zone.
  • a bubbler is provided on the upstream side of the crossing sill in order to control the upstream circulation flow and the downstream circulation flow.
  • the melting furnace (melting tank) described in Patent Document 2 does not have a structure corresponding to the transverse sill in the melting furnace described in Patent Document 1, but includes at least one row of bubblers and at least two opposite burners. It describes using glass to melt and clarify.
  • the melting furnaces described in Patent Documents 1 and 2 are not necessarily suitable for producing high-quality alkali-free glass.
  • T ⁇ As an index of the melting temperature of glass, T ⁇ , that is, a temperature at which the glass viscosity ⁇ becomes 10 2 [dPa ⁇ S] is used, but non-alkali glass has a T ⁇ of 1500 to 1760 ° C. Compared with alkali-containing glass such as lime glass, T ⁇ is 100 ° C. or higher, and homogenization is difficult.
  • the alkali-free glass has a higher T ⁇ than the alkali-containing glass such as soda lime glass, and therefore the temperature of the molten glass in the melting furnace inevitably increases. If the temperature of the molten glass is high, the erosion action of the molten glass on the in-furnace structure is enhanced accordingly. Therefore, in the case of non-alkali glass, there is a step that affects the flow of the molten glass at the bottom of the melting furnace, such as a crossing threshold in the melting furnace described in Patent Document 1 and a fining table in the melting furnace described in Patent Document 2. Then, the erosion of the level
  • the applicant of the present application has proposed a molten glass manufacturing apparatus described in Patent Document 3.
  • a bubbler first and second bubblers 13 and 14
  • the inside of the melting tank 10 can be provided without providing a step structure that affects the molten glass flow as described in Patent Documents 1 and 2 at the bottom of the molten glass channel.
  • the present invention provides a molten glass production method suitable for producing high-quality non-alkali glass with high homogeneity and a plate glass production method using the same in order to solve the above-described problems of the prior art. For the purpose.
  • the present invention is a molten glass production method for producing molten glass using a molten glass production apparatus having a melting tank for melting glass raw materials,
  • the dissolution tank has a burner for heating the upper space of the dissolution tank, In the vicinity of the bottom of the melting tank, there are a plurality of bubblers over the width direction of the molten glass flow path,
  • the distance from the upstream end of the molten glass flow path to the columns of said plurality of bubblers is 0.4 L F ⁇ 0.55 L F
  • the dissolution A method for producing a molten glass characterized in that the molten glass is produced under a condition that the flow of the molten glass in the tank satisfies the following (1) to (3).
  • the present invention also provides a plate glass manufacturing method in which the molten glass obtained by the molten glass manufacturing method of the present invention is formed into a plate glass.
  • the molten glass manufacturing method of the present invention is suitable for producing high-quality non-alkali glass with high homogeneity. Since the plate glass manufacturing method of this invention can manufacture plate glass with high homogeneity and high transparency, it is suitable for manufacture of the board
  • FIG. 1 is a cross-sectional view of an embodiment of a melting tank used in the molten glass production method of the present invention.
  • FIG. 2 is a plan view of the dissolution tank 10A shown in FIG. However, the upper wall surface of the dissolution tank 10A is omitted.
  • FIG. 3 is a cross-sectional view of another embodiment of the melting tank used in the molten glass production method of the present invention.
  • FIG. 4 is a plan view of the dissolution tank 10B shown in FIG. However, the upper wall surface of the dissolution tank 10B is omitted.
  • FIG. 1 is a cross-sectional view of an embodiment of a melting tank used in the molten glass production method of the present invention.
  • FIG. 2 is a plan view of the dissolution tank 10A shown in FIG. However, the upper wall surface of the dissolution tank 10A is omitted.
  • FIG. 3 is a cross-sectional view of another embodiment of the melting tank used in the molten glass production method of the present invention.
  • FIG. 5 is a graph comparing the frequency of occurrence for each number of bubbles in the molten glass when (V 2C ⁇ V 2S ) / V 2C is less than 0.05 and more than 0.5.
  • FIG. 6 is a graph comparing the frequency of occurrence for each number of bubbles in molten glass when (V 2C ⁇ V 2S ) / V 2C is less than 0.1 and greater than 0.5.
  • FIG. 7 is a graph comparing the frequency of occurrence for each number of bubbles in the molten glass when (V 2C ⁇ V 2S ) / V 2C is less than 0.3 and more than 0.5.
  • FIG. 8 is a graph comparing the frequency of occurrence for each number of bubbles in the molten glass when (V 2C ⁇ V 2S ) / V 2C is less than 0.5 and more than 0.5.
  • FIG. 1 is a cross-sectional view of an embodiment of a melting tank used in the molten glass manufacturing method of the present invention
  • FIG. 2 is a plan view of a melting tank 10A shown in FIG.
  • a glass raw material inlet 11 is provided at the upstream end of the melting tank 10A.
  • the glass raw material charged from the charging port 11 is melted by heating by the burner 15 to become molten glass G, and is held in the melting tank 10A.
  • a discharge port 12 for discharging the molten glass G to the next process is provided at the downstream end 10e of the melting tank 10A.
  • the discharge port 12 communicates with the downstream conduit 20.
  • a plurality of bubblers 13 are provided in the vicinity of the bottom surface of the dissolution tank 10A shown in FIGS.
  • the bubbler 13 is arranged at a predetermined interval (pitch) across the width direction of the melting tank 10A, more specifically, the width direction of the molten glass flow path of the melting tank 10A.
  • pitch a predetermined interval across the width direction of the melting tank 10A, more specifically, the width direction of the molten glass flow path of the melting tank 10A.
  • the suitable range of the pitch of each bubbler in the row direction of the bubbler 13 is mentioned later.
  • the burners 15 are provided at equal intervals over the entire length of the dissolution tank 10A.
  • the melting tank 10A shown in FIGS. 1 and 2 affects the molten glass flow as described in Patent Documents 1 and 2 at the bottom of the molten glass flow path by arranging the bubbler 13 in a specific arrangement described later. Without providing a step structure, it is possible to promote the formation of a circulating flow (the upstream circulating flow 100 and the downstream circulating flow 101) of the molten glass G in the melting tank 10.
  • the melting tank 10A shown in FIGS. 1 and 2 does not need to be provided with a step structure in which erosion by molten glass is a problem at the bottom of the molten glass flow path, so that T ⁇ is 1500 to 1760 ° C. It is suitable for the production of alkali-free glass that is 100 ° C.
  • alkali-free glass having a T ⁇ of 1500 to 1760 ° C. include alkali-free glass compositions 1 to 3 in which the mass percentage display based on the oxide has the following composition.
  • Alkali-free glass composition 1 In mass percentage display based on oxide, SiO 2 : 50 to 73% Al 2 O 3 : 10.5-24% B 2 O 3 : 0 to 12% MgO: 0-8% CaO: 0 to 14.5% SrO: 0-24% BaO: 0 to 13.5% MgO + CaO + SrO + BaO: 8 to 29.5% ZrO 2 : 0 to 5% Alkali-free glass containing
  • Alkali-free glass composition 2 In mass percentage display based on oxide, SiO 2 : 58 to 66% Al 2 O 3 : 15-22% B 2 O 3 : 5-12% MgO: 0-8% CaO: 0-9% SrO: 3 to 12.5% BaO: 0-2% MgO + CaO + SrO + BaO: 9-18% Alkali-free glass containing
  • the alkali-free glass composition 2 has a high strain point and is suitable when considering solubility.
  • Alkali-free glass composition 3 In mass percentage display based on oxide, SiO 2 : 54 to 73% Al 2 O 3 : 10.5 to 22.5% B 2 O 3 : 0 to 5.5% MgO: 0-8% CaO: 0-9% SrO: 0-16% BaO: 0 to 2.5% MgO + CaO + SrO + BaO: 8 to 26% Alkali-free glass containing
  • the alkali-free glass composition 3 is particularly suitable when considering a high strain point.
  • Dissolving tank 10A shown in FIGS. 1 and 2 when the length of molten glass flow path of the dissolution tank 10A and L F, the distance from the upstream end of the molten glass flow path, until row of bubblers 13, 0. 4L F to 0.55L F. Therefore, compared with the conventional melting tank (melting furnace) as described in Patent Documents 1 and 2, the length of the melting tank 10A is short, and the length of the part forming the downstream circulation flow in the melting tank is also short. .
  • the length L F of the molten glass flow path of melting tank 10A of this embodiment is different depending on the width W of the molten glass flow path is 10 ⁇ 30 m, preferably 10 ⁇ 25 m, more preferably 15 ⁇ 22m It is. On the other hand, the width W of the molten glass channel is 5 to 10 m, preferably 5.5 to 9 m, and more preferably 6.5 to 8 m.
  • the pitch p between the individual bubblers in the row direction of the bubblers that is, the distance between the individual bubblers in the width direction of the molten glass flow path of the melting tank 10A is 400 to 700 mm. If the pitch p between the individual bubblers is in the above range, it is excellent in the effect of promoting the formation of a circulating flow (upstream circulating flow 100, downstream circulating flow 101) of the molten glass G in the melting tank 10A, and upstream. It is preferable for controlling the flow rate of the side circulation flow 100 and the flow rate of the downstream circulation flow 101 to a specific range described later, and is excellent in terms of manufacturing cost.
  • the pitch p between the individual bubblers is more than 700 mm, the distance between the individual bubblers is too wide, so the molten glass G circulating flow (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10A
  • the effect of promoting the formation may be insufficient.
  • a difference occurs in the acceleration, and the flow rate of the circulating flow may be uneven, which is not preferable from the viewpoint of homogenizing the molten glass G.
  • the gas 16 supplied from the bubbler 13 that does not adversely affect the components of the melting tank 10A such as the molten glass G and the bubbler 13.
  • a gas that does not contain oxygen, such as nitrogen, helium, and argon, as the gas 16 supplied from the bubbler 13. Of these, nitrogen is particularly preferred.
  • molten glass is manufactured under the conditions that the flow of the molten glass G in the melting tank 10A shown in FIGS. 1 and 2 satisfies the following (1) to (3).
  • V 1C is set in the above range.
  • V 1C can be measured, for example by taking molten glass surface of bubbles and unmelted raw materials in the camera. However, you may measure in the procedure similar to V2C and V2S mentioned later.
  • the measurement position of V 1C in the flow direction of the molten glass in the melting tank 10A is the upstream end of the molten glass flow channel +500 mm.
  • a position of ⁇ 0.35L F is preferred. This is because it is suitable for capturing only the upstream surface flow that moves in the upstream direction of the melting tank 10A near the surface of the molten glass.
  • the measurement position of the V 1C means an arbitrary position within the described range (hereinafter, the same applies in this specification).
  • V 1C can be adjusted by the flow rate of the gas 16 from the bubbler 13. Specifically, increasing the flow rate of the gas 16 from the bubbler 13 increases V 1C , and decreasing the flow rate of the gas 16 decreases V 1C .
  • V 1C can also be adjusted by the ambient temperature T 1 above the bubbler 13. Specifically, when the ambient temperature T 1 above the bubbler 13 is increased, V 1C increases, and when the ambient temperature T 1 is decreased, V 1C decreases.
  • the average flow rate F of the gas 16 from the bubbler 13 is preferably 0.5 to 20 liters / minute, more preferably 0.7 to 5 liters / minute, More preferably, it is 0.9 to 3 liters / minute.
  • the atmospheric temperature T 1 above the bubbler 13 and T 2 described later are preferably 1590 to 1710 ° C., more preferably 1600 to 1695 ° C.
  • Ambient temperatures T 1 herein for example, the nearest burner upstream of the row of bubblers 13, and the nearest burner located further upstream of the burner, measured at the middle position.
  • the ambient temperature T 1 when adjusting V 1C can be adjusted by heating with the burner 15 upstream of the row of bubblers 13. Combustion in the burner 15 can be performed by mixing the fuel with oxygen gas and burning it, or mixing the fuel with oxygen gas and air and burning it. By using these methods, moisture can be contained in the molten glass. In the post-process of the molten glass sent from the melting tank 10A to the downstream conduit 20, when the bubbles in the molten glass are defoamed by vacuum degassing, it is preferable that the molten glass contains moisture. Therefore, the combustion as described above is preferable.
  • (3) When the average flow velocity of the downstream surface layer flow 103 in the vicinity of the side portion in the width direction of the dissolution tank 10A is V 2S ,
  • 0 to 0.5.
  • the side wall of the melting tank 10A is eroded by the molten glass, and its heat insulating action gradually decreases, so the vicinity of the center and the side in the width direction of the melting tank 10A As a result, a temperature difference occurs in the molten glass. Specifically, the temperature of the molten glass near the side portion is lower than that near the center in the width direction of the melting tank 10A. As a result, a flow velocity difference is generated in the downstream surface layer flow 103 between the vicinity of the center in the width direction of the dissolution tank 10A and the vicinity of the side portion.
  • the flow velocity of the downstream surface layer flow 103 near the side portion is lower than that near the center in the width direction of the dissolution tank 10A.
  • the difference in the flow velocity of the downstream surface layer flow 103 between the vicinity of the center in the width direction of the dissolution tank 10A and the vicinity of the side portion becomes large, the quality of the manufactured glass deteriorates.
  • V 2C exceeds 30 m / h
  • the residence time of the molten glass in the melting tank 10A is shortened, so that the quality of the produced glass is deteriorated.
  • it shall be 30 m / h or less.
  • it is 15 m / h or less, More preferably, it is 10 m / h or less.
  • V2C is less than 0.1 m / h, volatilization from the surface of the molten glass increases, and the quality of the glass to be produced decreases.
  • it is 1 m / h or more, More preferably, it is 2 m / h or more.
  • 0 to 0.01.
  • V 2C and V 2S can be measured by continuously capturing a downstream surface layer flow with a camera and using this image. Specifically, a dynamic region is extracted by performing background difference processing on an image captured by a camera, this is subjected to optical flow processing, and further subjected to geometric correction processing to obtain a real space (three-dimensional) speed. Ask for. However, since this numerical value varies to some extent, V 2C and V 2S are obtained as expected values estimated from the distribution of speeds measured in the specified region.
  • the measurement position of V 2C and V 2S in the molten glass channel direction in the melting tank 10A that is, the position where the downstream surface layer flow is photographed by the camera is the position of the molten glass channel.
  • the position is preferably 0.6 L F to L F ⁇ 500 mm from the upstream end. This is because it is suitable for capturing only the downstream surface layer flow that moves in the vicinity of the surface of the molten glass in the downstream direction of the melting tank 10.
  • the measurement position of V 2C in the width direction of the melting tank 10A is 2/5 W to 3/5 W when the width of the molten glass flow path of the melting tank 10A is W (mm).
  • the position is preferably 9/20 W to 11/20 W.
  • the measurement position of V 2S in the width direction of the dissolution tank 10A is preferably a position of 0 to 1 / 4W.
  • 0 indicates the vicinity of the side wall of the dissolution tank 10, specifically, a position within 20 mm from the side wall.
  • the measurement position of V 1C in the width direction of the dissolution tank 10 is preferably a position of 2 / 5W to 3 / 5W, preferably 9 / 20W to A position of 11/20 W is more preferable.
  • the range to capture the image of the downstream surface current is preferably in the following ranges.
  • Flow path direction of molten glass 100 mm to 3000 mm, more preferably 200 mm to 1000 mm, still more preferably 300 mm to 500 mm Dissolving tank 10A width direction: W / 75 to W / 5, more preferably W / 30 to W / 7, and still more preferably W / 16 to W / 14
  • the range in which the upstream surface flow image is captured is the same as described above.
  • range to capture the image of the downstream surface current is preferably in the following ranges.
  • Flow path direction of molten glass 200 mm to 3000 mm, more preferably 300 mm to 1500 mm, still more preferably 400 mm to 900 mm
  • the width direction of the dissolution tank 10 W / 30 to W / 2, more preferably W / 10 to W / 4, still more preferably W / 7 to W / 5
  • the range in which an image of the downstream surface layer flow is captured is a range that does not involve a drastic change in brightness due to the reflection of the frame.
  • V 2C in the condition (2) can be adjusted by the flow rate of the gas 16 from the bubbler 13. Specifically, when the flow rate of the gas 16 from the bubbler 13 is increased, V 2C increases, and when the flow rate of the gas 16 is decreased, V 2C decreases. V 2C can also be adjusted by the ambient temperature T 2 above the bubbler 13. Specifically, the higher the upper atmospheric temperature T 2 of the bubbler 13, an increase in V 2C, the lower the ambient temperature T 2, V 2C is reduced.
  • Ambient temperature T 2 in regulating V 2C includes a row of bubblers 13, and the nearest burner downstream from said bubbler, measured at an intermediate position.
  • the atmospheric temperature T 2 when adjusting V 2C can be adjusted by heating by the burner 15 on the downstream side of the row of bubblers 13.
  • the combustion in the burner 15 is as described above.
  • V 2C and V 2S in the condition (3) can be adjusted by heating with the burner 15 on the downstream side of the row of bubblers 13.
  • the difference between V 2C and V 2S is caused by a temperature difference in the molten glass between the center in the width direction of the melting tank 10A and the vicinity of the side, specifically, melting. This is because the temperature of the molten glass near the side portion is lower than that near the center in the width direction of the tank 10A.
  • the temperature of the molten glass near the side is increased by heating by the burner 15 on the downstream side of the row of bubblers 13, and the temperature difference between the molten glass near the center and the side in the width direction of the melting tank 10A. Can be reduced. As a result, the difference between V 2C and V 2S decreases, and the value of
  • V 2C and V 2S in the condition (3) can be adjusted by the flow rate of the gas 16 from the bubbler 13. Specifically, by increasing the flow rate of the gas 16 from the bubbler 13 near the side relative to the flow rate of the gas 16 from the bubbler 13 near the center in the width direction of the dissolution tank 10A, V 2C and V 2S And the value of
  • FIG. 3 is a cross-sectional view of another embodiment of the melting tank used in the molten glass production method of the present invention
  • FIG. 4 is a plan view of the melting tank shown in FIG.
  • a plurality of first bubblers 13A having different positions in the molten glass flow path direction of the dissolution tank 10B, and A plurality of second bubblers 13B are provided.
  • the first bubbler 13A is provided on the upstream side of the molten glass flow path with respect to the second bubbler 13B, and a predetermined distance is provided between the first bubbler 13A row and the second bubbler 13B row. Is provided. Note that the pitches of the individual bubblers in the row direction of the first bubbler 13A and the second bubbler 13B are the same as those described for the bubbler 13 of the dissolution tank 10A. A preferable range of the distance between the first bubbler 13A row and the second bubbler 13B row will be described later.
  • burners 15 are arranged on both sides of the melting tank 10B so as to be positioned above the molten glass G held in the melting tank 10B.
  • the burners 15 are provided at regular intervals throughout the entire length of the dissolution tank 10B, except for exceptions described later.
  • the melting tank 10B shown in FIGS. 3 and 4 is described in Patent Documents 1 and 2 at the bottom of the molten glass flow path by arranging the first and second bubblers 13A and 13B and the burner 15 in a specific arrangement described later.
  • the formation of a circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10B can be promoted without providing a step structure that affects the molten glass flow. It is better in terms.
  • T ⁇ is 1500 to 1760 ° C., which is suitable for the production of alkali-free glass that is 100 ° C. or higher compared to alkali-containing glass such as soda lime glass.
  • Dissolving tank 10B shown in FIGS. 3 and 4 when the length of molten glass flow path of the dissolution tank 10B and L F, the distance from the upstream end of the molten glass flow path to the row of first bubbler 13A, a 0.4L F ⁇ 0.5L F, the distance from the downstream end of the molten glass flow path to the row of the second bubblers 13B is 0.45L F ⁇ 0.55L F. Therefore, similarly to the dissolution tank 10A, the length of the dissolution tank 10B is shorter than the conventional dissolution tank (melting furnace) as described in Patent Documents 1 and 2, and the downstream circulating flow in the dissolution tank is reduced. The length of the site to be formed is also short.
  • the distance from the upstream end of the molten glass channel to the row of the first bubblers 13A is preferably 0.43L F to 0.46L F.
  • the distance from the downstream end to the row of second bubblers 13B is preferably 0.47L F to 0.54L F.
  • L P is 500 to 1000 mm.
  • L P satisfies the above range, it is excellent in the effect of promoting the formation of the circulating flow (upstream circulating flow 100, downstream circulating flow 101) of the molten glass G in the melting tank 10B, and upstream.
  • the flow velocity of the side circulation flow 100 and the flow velocity of the downstream circulation flow 101 can be controlled within a specific range described later.
  • L P is less than 500 mm, the distance between the row of the first bubblers 13A and the row of the second bubblers 13B is too close, so that the circulating flow of the molten glass G in the melting tank 10B (upstream circulating flow 100 In addition, the effect of promoting the formation of the downstream circulation flow 101) is poor, and it is difficult to control the flow rate of the upstream circulation flow 100 and the flow rate of the downstream circulation flow 101 to a specific range described later.
  • L P is preferably 600 to 800 mm.
  • the pitch p between individual bubblers in the row direction of the bubblers is the same as that described for the bubbler 13 of the dissolution tank 10A.
  • the first bubbler 13 ⁇ / b> A and the second bubbler 13 ⁇ / b> B are arranged so as not to be coaxial with respect to the flow direction of the molten glass in the melting tank 10 ⁇ / b> B shown in FIGS.
  • the first bubbler 13A and the second bubbler 13B are arranged in a staggered manner, and the protruding port of the first bubbler 13A and the protruding port of the second bubbler 13B are coaxial. Does not exist above.
  • gases 16A and 16B supplied from the first bubbler 13A and the second bubbler 13B are the same as described for the gas 16 supplied from the bubbler 13 of the dissolution tank 10A.
  • Burners 15 are provided at equal intervals over the entire length of the dissolution tank 10B on both sides of the dissolution tank 10B shown in FIGS. However, the burner 15 is not provided above the second bubbler 13B. This is to be lower than the ambient temperature T 1 of the upper atmosphere temperature T 2 above the second bubbler 13B first bubbler 13A. Thereby, the flow rate per unit time of the downstream circulation flow 101 can be made lower than that of the upstream circulation flow 100. This is because the flow rate per unit time is lower in the downstream circulation flow 101 for the purpose of homogenizing the molten glass than in the upstream circulation flow 100 for the purpose of melting and clarifying the glass raw material. It is because it is preferable.
  • the melt in the melting tank 10B The distance L B1 between the row of first bubblers 13A and the burner 15 closest to the upstream side of the row in the glass flow path direction, and the burner 15 nearest to the row of second bubblers 13B and the downstream side of the row It is necessary that the distance L B2 to be in a relationship of L B2 > L B1 . That is, the burner 15 is provided above the first bubbler 13A, whereas the burner 15 is not provided above the second bubbler 13B.
  • L B2 ⁇ L B1 ⁇ 300 mm is preferable, L B2 ⁇ L B1 ⁇ 500 mm is more preferable, and L B2 ⁇ L B1 ⁇ 800 mm is further preferable.
  • the burner 15 is provided above the row of the first bubblers 13A.
  • the nearest burner 15 may be arranged some distance away from the upstream side of the row.
  • the ambient temperature above the first bubbler 13A becomes too low and the upstream circulation flow 100 becomes weak, and the glass Problems such as insufficient melting of the raw materials and insufficient homogenization of the molten glass G in the downstream region of the melting tank 10 occur.
  • L B1 500 to 1500 mm is preferable.
  • molten glass is manufactured under the condition that the flow of the molten glass G in the melting tank 10B shown in FIGS. 3 and 4 satisfies the following (1) to (3).
  • V 1C is set in the above range to suppress the advance of a heterogeneous layer (scum layer) having a light specific gravity caused by undissolved material in the glass raw material or volatilization on the surface of the molten glass, and to promote homogenization of the molten glass. It is. About the measuring method of V1C and a measurement position, it is the same as having described about 10 A of dissolution tanks.
  • V 1C can be adjusted by the flow rate of the gas 16A from the first bubbler 13A. Specifically, when the flow rate of the gas 16A from the first bubbler 13A is increased, V 1C increases, and when the flow rate of the gas 16A is decreased, V 1C decreases. V 1C can also be adjusted by the ambient temperature T 1 above the first bubbler 13A. Specifically, the higher the ambient temperature T 1 of the upper first bubbler 13A, increased V 1C, the lower the ambient temperatures T 1, V 1C is reduced.
  • the average flow rate F 1 of the gas 16A from the first bubbler 13A is 0.5 to 20 l / min, is from 0.7 to 5 l / min Is more preferably 0.9 to 3 liters / minute.
  • the atmospheric temperature T 1 above the first bubbler 13A is preferably 1590 to 1710 ° C., more preferably 1600 to 1695 ° C.
  • the ambient temperature T 1 in this specification is measured at an intermediate position between, for example, the burner closest to the upstream side of the row of the first bubblers 13A and the burner closest to the upstream side of the burner. .
  • a specific measurement method is as described for the atmospheric temperature T 1 of the melting tank 10A.
  • Ambient temperatures T 1 may be adjusted by heating by the upstream side of the burner 15 than the row of the first bubbler 13A.
  • the combustion in the burner 15 is the same as that described for the dissolution tank 10A.
  • Condition (2) Of the downstream circulating flow 101 of the molten glass formed on the downstream side of the second bubbler 13B, the flow in the vicinity of the surface of the molten glass moving in the downstream direction of the melting tank 10B is the downstream side of the molten glass.
  • V 2C 0.1 to 30 m / h.
  • V 2S 0 to 0.5.
  • V 2C exceeds 30 m / h
  • the residence time of the molten glass in the melting tank 10B is shortened, so that the quality of the produced glass is deteriorated.
  • it shall be 30 m / h or less.
  • it is 15 m / h or less, More preferably, it is 10 m / h or less.
  • V2C is less than 0.1 m / h, volatilization from the surface of the molten glass increases, and the quality of the glass to be produced decreases.
  • it is 1 m / h or more, More preferably, it is 2 m / h or more.
  • V 2C in the condition (2) can be adjusted by the flow rate of the gas 16B from the second bubbler 13B. Specifically, when the flow rate of the gas 16B from the second bubbler 13B is increased, V 2C increases, and when the flow rate of the gas 16B is decreased, V 2C decreases. V 2C can also be adjusted by the ambient temperature T 2 above the second bubbler 13B. Specifically, the higher the upper atmospheric temperature T 2 of the second bubbler 13B, increased V 2C, the lower the ambient temperature T 2, V 2C is reduced.
  • the average flow rate F 2 of the gas 16B from the second bubbler 13B is preferably 0.3 to 19.8 liters / minute, preferably 0.4 to 4.8 liters / minute. More preferably, it is 0.5 to 2 liters / minute.
  • ambient temperature T 2 above the second bubbler 13B is 1590 ⁇ 1710 ° C., and more preferably 1600 ⁇ 1695 ° C..
  • Ambient temperature T 2 in the present specification for example, a column of the second bubbler 13B, the nearest burner downstream from said bubbler, measured at an intermediate position.
  • Ambient temperature T 2 can be adjusted by heating by a burner 15 on the downstream side of the row of the second bubblers 13B.
  • the combustion in the burner 15 is as described above.
  • V 2C and V 2S in condition (3) can be adjusted by heating by the burner 15 on the downstream side of the second bubbler 13B row. Specifically, the temperature of the molten glass near the side is raised by heating by the burner 15 downstream from the row of second bubblers 13B, and the vicinity of the center in the width direction of the melting tank 10B and the vicinity of the side The temperature difference of the molten glass can be reduced. As a result, the difference between V 2C and V 2S decreases, and the value of
  • V 2C and V 2S in the condition (3) can be adjusted by the flow rate of the gas 16B from the second bubbler 13B. Specifically, by increasing the flow rate of the gas 16B from the second bubbler 13B near the side portion relative to the flow rate of the gas 16B from the second bubbler 13B near the center in the width direction of the dissolution tank 10B, The difference between V 2C and V 2S decreases, and the value of
  • the constituent material of the melting tanks 10A and 10B that contact the molten glass G is required to be excellent in heat resistance and corrosion resistance to the molten glass, and thus a refractory brick containing ZrO 2 is used.
  • a refractory brick containing ZrO 2 is used.
  • the portion of 0.1L F to 0.3L F upstream from the row of the bubblers 13 and the first bubblers 13A has a ZrO 2 content of 85% or more and 97% by mass.
  • each hot-melt refractory is preferably 50 to 120 mm, and two to three hot-melt refractories are preferably laminated. Further, 2 to 5 layers of other refractory bricks containing ZrO 2 can be laminated on the outside of the layer of the hot-melt refractory thus formed.
  • each refractory brick can be laminated
  • the plate glass manufacturing method of the present invention the molten glass obtained by the above-described molten glass manufacturing method of the present invention is formed into a plate glass.
  • various forming methods such as a float method and a downdraw method can be used. In the case of a glass having a T ⁇ of 1500 to 1760 ° C., the float method is particularly preferable.
  • bubbles in the molten glass may be degassed by vacuum degassing.
  • the plate glass manufacturing method of the present invention since the molten glass having high homogeneity obtained by the molten glass manufacturing method of the present invention is formed into a plate glass, a plate glass having high homogeneity and high transparency can be obtained.
  • the plate glass production apparatus of the present invention can be applied to the production of plate glass for various uses. However, since a plate glass having high homogeneity and high transparency can be obtained, the homogeneity of the glass substrate for FPD can be obtained. It is particularly preferable to apply it to the production of plate glass for applications in which the demands of these are extremely strict.
  • Glass raw materials are introduced into the inlet of the melting tank 10B shown in FIGS. 3 and 4 so as to have a desired composition, and alkali-free glass having T ⁇ of 1500 to 1760 ° C. is manufactured.
  • the dimensions of each part of the dissolution tank 10B shown in FIGS. 3 and 4 are as follows.
  • Molten glass flow path length L F 16 to 25 m Molten glass channel width: 5.5-9m Distance from the upstream end of the molten glass flow path to the first bubbler 13A row: 0.43L F to 0.46L F Distance from the downstream end of the molten glass flow path to the row of second bubblers 13B: 0.47L F to 0.54L F Distance L P between first row of bubblers 13A and second row of bubblers 13B: 600 to 800 mm Pitch p of individual bubblers 13A and 13B in the row direction of the bubblers: 400 to 700 mm Distance L B1 between the row of first bubblers 13A and the burner 15 closest to the upstream side of the row in the flow direction of the molten glass in the melting tank: 500 to 1500 mm Distance L B2 between the row of second bubblers 13B and the burner 15 closest to the downstream side of the row in the flow direction of the molten glass in the melting tank: 1000 to 2000 mm L B2 -L B1 ⁇ 500mm Distance between individual burners in the flow direction of the
  • V 2C average flow velocity V 2C of the downstream surface layer flow near the center in the width direction of the dissolution tank
  • V 2C 0.1 to 30 m / h.
  • the horizontal axis of FIG. 5 is an index when the predetermined number of bubbles in the molten glass is 1, and the vertical axis is the ratio of the number of measurement data.
  • the number of bubbles in the molten glass is from a drain pipe (not shown) connected in the vertical direction with respect to the conduit 20 communicating with the discharge port 12 provided at the downstream end portion 10e of the melting tank 10.
  • the molten glass under flow was collected as a sample and measured. Specifically: The molten glass was imaged intermittently at a predetermined imaging interval (35 msec) with an inspection device equipped with an electronic camera, and the captured image was binarized to detect a bubble image in the molten glass as a white image.
  • the number of white images, which are defect images, is counted as the number of defects by a calculation unit built in the inspection apparatus. Further, by calculating the amount of movement of bubbles and calculating the flow rate per unit time flowing down from the drain pipe, the number of bubbles was calculated as the number per unit molten glass flowing down. Also, when (V 2C ⁇ V 2S ) / V 2C ⁇ 0.1 and (V 2C ⁇ V 2S ) / V 2C >0.5; (V 2C ⁇ V 2S ) / V 2C ⁇ 0.

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Abstract

　The present invention is a manufacturing method for molten glass which uses a molten glass manufacturing device having a melting tank for melting glass starting materials to produce molten glass, wherein the melting tank has a burner for heating the upper space of the melting tank, and a plurality of bubblers across the width direction of the molten glass passage in the vicinity of the bottom surface of the melting tank. The plurality of bubblers are positioned so as to satisfy a predetermined positional relationship with respect to the length of the molten glass passage of the melting tank, and the flow of molten glass in the melting tank produces molten glass under predetermined conditions.

Description

溶融ガラス製造方法およびそれを用いた板ガラスの製造方法Molten glass manufacturing method and plate glass manufacturing method using the same
　本発明は、溶融ガラス製造方法およびそれを用いた板ガラスの製造方法に関する。より具体的には、均質性の高い高品質な無アルカリガラスを生産するための溶融ガラス製造方法およびそれを用いた板ガラスの製造方法に関する。 The present invention relates to a molten glass production method and a plate glass production method using the same. More specifically, the present invention relates to a molten glass manufacturing method for producing high-quality non-alkali glass with high homogeneity and a manufacturing method of plate glass using the same.
　フラットパネルディスプレイ（ＦＰＤ）用のガラス基板の製造には、実質的にアルカリ金属イオンを含まない無アルカリガラスを用いることが、ガラス基板の絶縁性を高めるために好ましい。また、無アルカリガラスは熱膨張係数が小さい点でもＦＰＤ用のガラス基板の製造に好ましい。 In the production of a glass substrate for a flat panel display (FPD), it is preferable to use an alkali-free glass that does not substantially contain alkali metal ions in order to increase the insulating properties of the glass substrate. In addition, alkali-free glass is preferable for the production of a glass substrate for FPD because it has a small coefficient of thermal expansion.
　ＦＰＤ用のガラス基板の製造においては、なお一層の高品質化、すなわち、均質性の高い高品質なガラス基板の製造が求められている。このためガラス原料を溶解して溶融ガラスを得る溶解槽（溶融炉）では溶融ガラスの均質性を高めるために様々な工夫がなされている。 In the manufacture of glass substrates for FPD, there is a demand for still higher quality, that is, the manufacture of high-quality glass substrates with high homogeneity. For this reason, in the melting tank (melting furnace) which melts a glass raw material and obtains molten glass, various ideas are made in order to improve the homogeneity of molten glass.
　特許文献１に記載の溶融炉では、横断敷居により溶融炉を上流帯域と下流帯域とに分け、各々の帯域で溶融ガラスの循環流（上流側循環流、下流側循環流）を形成させることにより、原料の溶解および溶融ガラスの均質化を行っている。より具体的には、上流帯域では上流側循環流を形成することによりガラス原料の溶解を行い、下流帯域では下流側循環流を形成することにより溶融ガラスの均質化を行う。特許文献１に記載の溶融炉では、上流側循環流および下流側循環流を制御するために、横断敷居の上流側にバブラーが設けられている。 In the melting furnace described in Patent Document 1, the melting furnace is divided into an upstream zone and a downstream zone by crossing sill, and a molten glass circulation flow (upstream circulation flow, downstream circulation flow) is formed in each zone. , Melting raw materials and homogenizing molten glass. More specifically, the glass raw material is melted by forming an upstream circulation flow in the upstream zone, and the molten glass is homogenized by forming a downstream circulation flow in the downstream zone. In the melting furnace described in Patent Document 1, a bubbler is provided on the upstream side of the crossing sill in order to control the upstream circulation flow and the downstream circulation flow.
　特許文献２に記載の溶融炉（溶融タンク）は、特許文献１に記載の溶融炉における横断敷居に相当する構造は有していないが、少なくとも１列のバブラーと少なくとも２つの互いに向かい合ったバーナーを用いてガラスを溶融、清澄することについて記載されている。
　しかしながら、特許文献１，２に記載の溶融炉は、高品質な無アルカリガラスを生産するのには必ずしも適していなかった。
　ガラスの溶解温度の指標には、Ｔη、すなわち、ガラス粘度ηが１０２［ｄＰａ・Ｓ］となる温度が用いられるが、無アルカリガラスはＴηが１５００～１７６０℃であり、通常のソーダライムガラス等のアルカリ含有ガラスに比べてＴηが１００℃以上高く、均質化が難しい。このため、特許文献１，２に記載のソーダライムガラス等の一般的な大量生産用等のレイアウトの溶融炉では十分均質化することができず、均質性に対する要求が特に厳しいガラス製品（ＦＰＤ用のガラス基板等）の製造には必ずしも適していなかった。 The melting furnace (melting tank) described in Patent Document 2 does not have a structure corresponding to the transverse sill in the melting furnace described in Patent Document 1, but includes at least one row of bubblers and at least two opposite burners. It describes using glass to melt and clarify.
However, the melting furnaces described in Patent Documents 1 and 2 are not necessarily suitable for producing high-quality alkali-free glass.
As an index of the melting temperature of glass, T η , that is, a temperature at which the glass viscosity η becomes 10 2 [dPa · S] is used, but non-alkali glass has a T η of 1500 to 1760 ° C. Compared with alkali-containing glass such as lime glass, T η is 100 ° C. or higher, and homogenization is difficult. For this reason, it cannot be sufficiently homogenized in a melting furnace having a layout for general mass production such as soda lime glass described in Patent Documents 1 and 2, and glass products (for FPDs) that require particularly high homogeneity. It was not necessarily suitable for the production of glass substrates and the like.
　また、上述したように、無アルカリガラスはソーダライムガラス等のアルカリ含有ガラスに比べてＴηが高いため、溶融炉内における溶融ガラスの温度も必然的に高くなる。溶融ガラスの温度が高ければ、それに応じて溶融ガラスによる炉内構造物への侵食作用が強くなる。したがって、無アルカリガラスの場合、特許文献１に記載の溶融炉における横断敷居や特許文献２に記載の溶融炉における清澄台のような、溶融炉の底部に溶融ガラス流に影響を与える段差が存在すると、溶融ガラスによる段差の侵食、および、それによる不純物の発生が問題となる。 Further, as described above, the alkali-free glass has a higher T η than the alkali-containing glass such as soda lime glass, and therefore the temperature of the molten glass in the melting furnace inevitably increases. If the temperature of the molten glass is high, the erosion action of the molten glass on the in-furnace structure is enhanced accordingly. Therefore, in the case of non-alkali glass, there is a step that affects the flow of the molten glass at the bottom of the melting furnace, such as a crossing threshold in the melting furnace described in Patent Document 1 and a fining table in the melting furnace described in Patent Document 2. Then, the erosion of the level | step difference by molten glass and generation | occurrence | production of the impurity by it become a problem.
　また、無アルカリガラスの場合、溶融炉内における溶融ガラスの温度が必然的に高くなるので、特許文献１のように下流帯域が長い構造や、特許文献２のように大型の溶融炉とすると、バーナーを用いて加熱する範囲が広くなることからエネルギー効率的に不利である。また、溶融ガラスによる侵食およびそれによる不純物の発生や、溶融ガラスの流速の変化も問題となる。 In the case of non-alkali glass, the temperature of the molten glass in the melting furnace is inevitably high. Therefore, when a structure having a long downstream zone as in Patent Document 1 or a large melting furnace as in Patent Document 2, It is disadvantageous in terms of energy efficiency because the range of heating using a burner is widened. Further, erosion by the molten glass, generation of impurities due thereto, and change in the flow rate of the molten glass are also problematic.
　上記した問題点を解決するため、本願出願人は、特許文献３に記載の溶融ガラス製造装置を提案している。特許文献３に記載の溶融ガラス製造装置では、ガラス原料を溶解するための溶解槽１０の底面近傍に設けるバブラー（第１，２のバブラー１３，１４）、および、溶解槽１０の上部空間を加熱するバーナー１５を特定の配置にすることにより、溶融ガラス流路の底部に特許文献１、２に記載されているような溶融ガラス流に影響を与える段差構造を設けることなしに、溶解槽１０内での溶融ガラスの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進し、かつ、上流側循環流１００の流速と下流側循環流１０１の流速とを所定の関係になるように制御することにより、均質性の高い高品質な無アルカリガラスを生産することができる（文中の符号はいずれも、特許文献３での記載通り）。 In order to solve the above-mentioned problems, the applicant of the present application has proposed a molten glass manufacturing apparatus described in Patent Document 3. In the molten glass manufacturing apparatus described in Patent Document 3, a bubbler (first and second bubblers 13 and 14) provided in the vicinity of the bottom surface of the melting tank 10 for melting the glass raw material and an upper space of the melting tank 10 are heated. By arranging the burner 15 to be in a specific arrangement, the inside of the melting tank 10 can be provided without providing a step structure that affects the molten glass flow as described in Patent Documents 1 and 2 at the bottom of the molten glass channel. The formation of the molten glass circulation flow (upstream circulation flow 100, downstream circulation flow 101) at the same time is promoted, and the flow rate of the upstream circulation flow 100 and the flow velocity of the downstream circulation flow 101 are in a predetermined relationship. By controlling in this way, it is possible to produce high-quality non-alkali glass with high homogeneity (all symbols in the sentence are as described in Patent Document 3).
日本国特開平９－１２４３２３号公報Japanese Laid-Open Patent Publication No. 9-124323 日本国特開平７－１４４９２３号公報Japanese Laid-Open Patent Publication No. 7-144923 国際公開２０１１／０３６９３９号International Publication No. 2011/036939
　上述したように、特許文献３に記載のガラス製造装置を用いることで、均質性の高い高品質な無アルカリガラスを生産することができる。
　しかしながら、ＦＰＤ用のガラス基板の仕様に関する要求は年々厳しくなるため、それに対応するため、製造されるガラスのさらなる均質化が望ましい。 As described above, by using the glass manufacturing apparatus described in Patent Document 3, high-quality alkali-free glass with high homogeneity can be produced.
However, since the requirements regarding the specifications of the glass substrate for FPD become stricter year by year, it is desirable to further homogenize the glass to be manufactured in order to meet the demand.
　本発明は、上記した従来技術の問題点を解決するため、均質性の高い高品質な無アルカリガラスを生産するのに適した溶融ガラス製造方法、および、それを用いた板ガラス製造方法を提供することを目的とする。 The present invention provides a molten glass production method suitable for producing high-quality non-alkali glass with high homogeneity and a plate glass production method using the same in order to solve the above-described problems of the prior art. For the purpose.
　上記した目的を達成するため、本発明は、ガラス原料を溶解するための溶解槽を有する溶融ガラス製造装置を用いて溶融ガラスを製造する溶融ガラス製造方法であって、
　前記溶解槽は、該溶解槽の上部空間を加熱するためのバーナーを有し、
　該溶解槽底面近傍に、溶融ガラス流路の幅方向にわたって複数のバブラーを有し、
　前記溶解槽の溶融ガラス流路の長さをＬＦとするとき、前記溶融ガラス流路の上流端から前記複数のバブラーの列までの距離が０．４ＬＦ～０．５５ＬＦであり
　前記溶解槽での溶融ガラスの流れが、下記（１）～（３）を満たす条件で溶融ガラスを製造することを特徴とする溶融ガラス製造方法。
（１）前記複数のバブラーよりも上流側に形成される溶融ガラスの上流側循環流のうち、前記溶解槽の上流方向に移動する、溶融ガラスの表面付近の流れを、溶融ガラスの上流側表層流とし、前記溶解槽の幅方向における中央付近における、該上流側表層流の平均流速をＶ１Ｃとするとき、Ｖ１Ｃが０ｍ／ｈ超２０ｍ／ｈ以下。
（２）前記複数のバブラーよりも下流側に形成される溶融ガラスの下流側循環流のうち、前記溶解槽の下流方向に移動する、溶融ガラスの表面付近の流れを、溶融ガラスの下流側表層流とし、前記溶解槽の幅方向における中央付近における、該下流側表層流の平均流速をＶ２Ｃとするとき、Ｖ２Ｃ＝０．１～３０ｍ／ｈ。
（３）前記溶解槽の幅方向における側部付近における、前記下流側表層流の平均流速をＶ２Ｓとするとき、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．５。 In order to achieve the above object, the present invention is a molten glass production method for producing molten glass using a molten glass production apparatus having a melting tank for melting glass raw materials,
The dissolution tank has a burner for heating the upper space of the dissolution tank,
In the vicinity of the bottom of the melting tank, there are a plurality of bubblers over the width direction of the molten glass flow path,
When the length of molten glass flow path of the melting tank and L F, the distance from the upstream end of the molten glass flow path to the columns of said plurality of bubblers is 0.4 L F ~ 0.55 L F the dissolution A method for producing a molten glass, characterized in that the molten glass is produced under a condition that the flow of the molten glass in the tank satisfies the following (1) to (3).
(1) Out of the upstream circulating flow of molten glass formed upstream of the plurality of bubblers, the flow near the surface of the molten glass that moves in the upstream direction of the melting tank is used as the upstream surface layer of the molten glass. When the average flow velocity of the upstream surface layer flow near the center in the width direction of the dissolution tank is V 1C , V 1C is more than 0 m / h and not more than 20 m / h.
(2) Out of the downstream circulation flow of the molten glass formed downstream of the plurality of bubblers, the flow near the surface of the molten glass that moves in the downstream direction of the melting tank is used as the downstream surface layer of the molten glass. and flow, in the vicinity of the center in the width direction of the melting tank, when the average flow velocity of the downstream side surface current and V 2C, V 2C = 0.1 ~ 30m / h.
(3) When the average flow velocity of the downstream surface layer flow in the vicinity of the side portion in the width direction of the dissolution tank is V 2S , | (V 2C −V 2S ) / V 2C | = 0 to 0.5.
　また、本発明は、本発明の溶融ガラス製造方法により得られた溶融ガラスを板ガラスに成形する板ガラス製造方法を提供する。 The present invention also provides a plate glass manufacturing method in which the molten glass obtained by the molten glass manufacturing method of the present invention is formed into a plate glass.
　本発明の溶融ガラス製造方法は、均質性の高い高品質な無アルカリガラスを生産に好適である。
　本発明の板ガラス製造方法は、均質性が高く、透明性が高い板ガラスを製造することができるため、ＦＰＤ用の基板の製造に好適である。 The molten glass manufacturing method of the present invention is suitable for producing high-quality non-alkali glass with high homogeneity.
Since the plate glass manufacturing method of this invention can manufacture plate glass with high homogeneity and high transparency, it is suitable for manufacture of the board | substrate for FPD.
図１は、本発明の溶融ガラス製造方法に用いる溶解槽の一実施形態の断面図である。FIG. 1 is a cross-sectional view of an embodiment of a melting tank used in the molten glass production method of the present invention. 図２は、図１に示す溶解槽１０Ａの平面図である。但し、溶解槽１０Ａの上部壁面は省略されている。FIG. 2 is a plan view of the dissolution tank 10A shown in FIG. However, the upper wall surface of the dissolution tank 10A is omitted. 図３は、本発明の溶融ガラス製造方法に用いる溶解槽の別の一実施形態の断面図である。FIG. 3 is a cross-sectional view of another embodiment of the melting tank used in the molten glass production method of the present invention. 図４は、図３に示す溶解槽１０Ｂの平面図である。但し、溶解槽１０Ｂの上部壁面は省略されている。FIG. 4 is a plan view of the dissolution tank 10B shown in FIG. However, the upper wall surface of the dissolution tank 10B is omitted. 図５は、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃが、０．０５未満の場合と、０．５超の場合について、溶融ガラス中の泡数ごとの発生頻度を比較したグラフである。FIG. 5 is a graph comparing the frequency of occurrence for each number of bubbles in the molten glass when (V 2C −V 2S ) / V 2C is less than 0.05 and more than 0.5. 図６は、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃが、０．１未満の場合と、０．５超の場合について、溶融ガラス中の泡数ごとの発生頻度を比較したグラフである。FIG. 6 is a graph comparing the frequency of occurrence for each number of bubbles in molten glass when (V 2C −V 2S ) / V 2C is less than 0.1 and greater than 0.5. 図７は、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃが、０．３未満の場合と、０．５超の場合について、溶融ガラス中の泡数ごとの発生頻度を比較したグラフである。FIG. 7 is a graph comparing the frequency of occurrence for each number of bubbles in the molten glass when (V 2C −V 2S ) / V 2C is less than 0.3 and more than 0.5. 図８は、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃが、０．５未満の場合と、０．５超の場合について、溶融ガラス中の泡数ごとの発生頻度を比較したグラフである。FIG. 8 is a graph comparing the frequency of occurrence for each number of bubbles in the molten glass when (V 2C −V 2S ) / V 2C is less than 0.5 and more than 0.5.
　以下、図面を参照して本発明について説明する。
　図１は、本発明の溶融ガラス製造方法に用いる溶解槽の一実施形態の断面図であり、図２は、図１に示す溶解槽１０Ａの平面図である。但し、理解を容易にするため、溶解槽１０Ａの上部壁面は省略されている。
　溶解槽１０Ａの上流側の端部にはガラス原料の投入口１１が設けられている。投入口１１から投入されたガラス原料は、バーナー１５による加熱によって溶解して溶融ガラスＧとなり、溶解槽１０Ａ内に保持される。溶解槽１０Ａの下流側の端部１０ｅには、溶融ガラスＧを次工程に払出すための払出し口１２が設けられている。払出し口１２は下流側の導管２０と連通している。 The present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of an embodiment of a melting tank used in the molten glass manufacturing method of the present invention, and FIG. 2 is a plan view of a melting tank 10A shown in FIG. However, the upper wall surface of the dissolution tank 10A is omitted for easy understanding.
A glass raw material inlet 11 is provided at the upstream end of the melting tank 10A. The glass raw material charged from the charging port 11 is melted by heating by the burner 15 to become molten glass G, and is held in the melting tank 10A. A discharge port 12 for discharging the molten glass G to the next process is provided at the downstream end 10e of the melting tank 10A. The discharge port 12 communicates with the downstream conduit 20.
　図１、２に示す溶解槽１０Ａの底面近傍には、複数のバブラー１３が設けられている。
　バブラー１３は、溶解槽１０Ａの幅方向、より具体的には、溶解槽１０Ａの溶融ガラス流路の幅方向、にわたって所定の間隔（ピッチ）を開けて配設されている。
　なお、バブラー１３の列方向における個々のバブラーのピッチの好適範囲については後述する。 A plurality of bubblers 13 are provided in the vicinity of the bottom surface of the dissolution tank 10A shown in FIGS.
The bubbler 13 is arranged at a predetermined interval (pitch) across the width direction of the melting tank 10A, more specifically, the width direction of the molten glass flow path of the melting tank 10A.
In addition, the suitable range of the pitch of each bubbler in the row direction of the bubbler 13 is mentioned later.
　図１、２に示す溶解槽１０Ａの両側面には、該溶解槽１０Ａ内に保持された溶融ガラスＧよりも上方に位置するようにバーナー１５が配置されている。バーナー１５は、溶解槽１０Ａの長さ方向全体にわたって等間隔で設けられている。 1 and 2 are disposed on both sides of the melting tank 10A shown in FIGS. 1 and 2 so as to be positioned above the molten glass G held in the melting tank 10A. The burners 15 are provided at equal intervals over the entire length of the dissolution tank 10A.
　図１、２に示す溶解槽１０Ａは、バブラー１３を後述する特定の配置にすることにより、溶融ガラス流路の底部に特許文献１、２に記載されているような溶融ガラス流に影響を与える段差構造を設けることなしに、溶解槽１０内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進することができる。
　図１，２に示す溶解槽１０Ａは、溶融ガラス流路の底部に溶融ガラスによる侵食が問題となる段差構造を設ける必要がないため、Ｔηが１５００～１７６０℃であり、ソーダライムガラス等のアルカリ含有ガラスに比べて１００℃以上高い無アルカリガラスの製造に好適である。
　Ｔηが１５００～１７６０℃となる無アルカリガラスの具体例としては、酸化物基準の質量百分率表示が下記組成となる無アルカリガラス組成１～３が例示できる。 The melting tank 10A shown in FIGS. 1 and 2 affects the molten glass flow as described in Patent Documents 1 and 2 at the bottom of the molten glass flow path by arranging the bubbler 13 in a specific arrangement described later. Without providing a step structure, it is possible to promote the formation of a circulating flow (the upstream circulating flow 100 and the downstream circulating flow 101) of the molten glass G in the melting tank 10.
The melting tank 10A shown in FIGS. 1 and 2 does not need to be provided with a step structure in which erosion by molten glass is a problem at the bottom of the molten glass flow path, so that T η is 1500 to 1760 ° C. It is suitable for the production of alkali-free glass that is 100 ° C. or more higher than alkali-containing glass.
Specific examples of the alkali-free glass having a T η of 1500 to 1760 ° C. include alkali-free glass compositions 1 to 3 in which the mass percentage display based on the oxide has the following composition.
無アルカリガラス組成１
　酸化物基準の質量百分率表示で、
ＳｉＯ２：５０～７３％
Ａｌ２Ｏ３：１０．５～２４％
Ｂ２Ｏ３：０～１２％
ＭｇＯ：０～８％
ＣａＯ：０～１４．５％
ＳｒＯ：０～２４％
ＢａＯ：０～１３．５％
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ：８～２９．５％
ＺｒＯ２：０～５％
を含有する無アルカリガラス。 Alkali-free glass composition 1
In mass percentage display based on oxide,
SiO 2 : 50 to 73%
Al 2 O 3 : 10.5-24%
B 2 O 3 : 0 to 12%
MgO: 0-8%
CaO: 0 to 14.5%
SrO: 0-24%
BaO: 0 to 13.5%
MgO + CaO + SrO + BaO: 8 to 29.5%
ZrO 2 : 0 to 5%
Alkali-free glass containing
無アルカリガラス組成２
　酸化物基準の質量百分率表示で、
ＳｉＯ２：５８～６６％
Ａｌ２Ｏ３：１５～２２％
Ｂ２Ｏ３：５～１２％
ＭｇＯ：０～８％
ＣａＯ：０～９％
ＳｒＯ：３～１２．５％
ＢａＯ：０～２％
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ：９～１８％
を含有する無アルカリガラス。
　無アルカリガラス組成２は、歪点が高く溶解性を考慮する場合に好適である。 Alkali-free glass composition 2
In mass percentage display based on oxide,
SiO 2 : 58 to 66%
Al 2 O 3 : 15-22%
B 2 O 3 : 5-12%
MgO: 0-8%
CaO: 0-9%
SrO: 3 to 12.5%
BaO: 0-2%
MgO + CaO + SrO + BaO: 9-18%
Alkali-free glass containing
The alkali-free glass composition 2 has a high strain point and is suitable when considering solubility.
無アルカリガラス組成３
　酸化物基準の質量百分率表示で、
ＳｉＯ２：  ５４～７３％
Ａｌ２Ｏ３：  １０．５～２２．５％
Ｂ２Ｏ３：  ０～５．５％
ＭｇＯ：  ０～８％
ＣａＯ：  ０～９％
ＳｒＯ：  ０～１６％
ＢａＯ：  ０～２．５％
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ：８～２６  ％
を含有する無アルカリガラス。
　無アルカリガラス組成３は、特に高歪点を考慮する場合に好適である。 Alkali-free glass composition 3
In mass percentage display based on oxide,
SiO 2 : 54 to 73%
Al 2 O 3 : 10.5 to 22.5%
B 2 O 3 : 0 to 5.5%
MgO: 0-8%
CaO: 0-9%
SrO: 0-16%
BaO: 0 to 2.5%
MgO + CaO + SrO + BaO: 8 to 26%
Alkali-free glass containing
The alkali-free glass composition 3 is particularly suitable when considering a high strain point.
　図１，２に示す溶解槽１０Ａは、該溶解槽１０Ａの溶融ガラス流路の長さをＬＦとするとき、溶融ガラス流路の上流端から、バブラー１３の列までの距離が、０．４ＬＦ～０．５５ＬＦである。
　したがって、特許文献１，２に記載されているような従来の溶解槽（溶融炉）に比べて、溶解槽１０Ａの長さが短く、溶解槽における下流側循環流を形成する部位の長さも短い。
　本実施形態の溶解槽１０Ａの溶融ガラス流路の長さＬＦは、溶融ガラス流路の幅Ｗによって異なるが、１０～３０ｍであり、好ましくは１０～２５ｍであり、より好ましくは１５～２２ｍである。
　一方、溶融ガラス流路の幅Ｗは、５～１０ｍであり、好ましくは５．５～９ｍであり、より好ましくは６．５～８ｍである。 Dissolving tank 10A shown in FIGS. 1 and 2, when the length of molten glass flow path of the dissolution tank 10A and L F, the distance from the upstream end of the molten glass flow path, until row of bubblers 13, 0. 4L F to 0.55L F.
Therefore, compared with the conventional melting tank (melting furnace) as described in Patent Documents 1 and 2, the length of the melting tank 10A is short, and the length of the part forming the downstream circulation flow in the melting tank is also short. .
The length L F of the molten glass flow path of melting tank 10A of this embodiment is different depending on the width W of the molten glass flow path is 10 ~ 30 m, preferably 10 ~ 25 m, more preferably 15 ~ 22m It is.
On the other hand, the width W of the molten glass channel is 5 to 10 m, preferably 5.5 to 9 m, and more preferably 6.5 to 8 m.
　バブラー１３において、バブラーの列方向における個々のバブラー間のピッチｐ、すなわち、溶解槽１０Ａの溶融ガラス流路の幅方向における個々のバブラー間の距離が、４００～７００ｍｍであることが好ましい。個々のバブラー間のピッチｐが上記の範囲であれば、溶解槽１０Ａ内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進する効果に優れ、上流側循環流１００の流速、および、下流側循環流１０１の流速を後述する特定の範囲に制御するうえで好ましく、かつ製造コストの観点でも優れている。
　個々のバブラー間のピッチｐが７００ｍｍ超だと、個々のバブラー間の距離が広すぎるため、溶解槽１０Ａ内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進する効果が不十分となるおそれがあり、特に、溶融ガラス流路の幅方向において、部位によって、溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成の促進に差が生じ、循環流の流速にムラが生じるおそれがあり、溶融ガラスＧの均質化という点から好ましくない。また、上流側循環流１００の流速、および、下流側循環流１０１の流速を後述する特定の範囲に制御するのが困難である。
　一方、個々のバブラー間のピッチｐを４００ｍｍ未満としても、溶解槽１０内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成の促進にはもはや寄与せず、むしろ、費用対効果の観点では溶解槽１０内に設けるバブラー１３の数が過剰となり、溶融ガラスの製造コストの増加につながることから好ましくない。 In the bubbler 13, it is preferable that the pitch p between the individual bubblers in the row direction of the bubblers, that is, the distance between the individual bubblers in the width direction of the molten glass flow path of the melting tank 10A is 400 to 700 mm. If the pitch p between the individual bubblers is in the above range, it is excellent in the effect of promoting the formation of a circulating flow (upstream circulating flow 100, downstream circulating flow 101) of the molten glass G in the melting tank 10A, and upstream. It is preferable for controlling the flow rate of the side circulation flow 100 and the flow rate of the downstream circulation flow 101 to a specific range described later, and is excellent in terms of manufacturing cost.
If the pitch p between the individual bubblers is more than 700 mm, the distance between the individual bubblers is too wide, so the molten glass G circulating flow (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10A There is a possibility that the effect of promoting the formation may be insufficient. In particular, in the width direction of the molten glass flow path, the formation of the circulating flow (the upstream circulating flow 100 and the downstream circulating flow 101) of the molten glass G depending on the part. A difference occurs in the acceleration, and the flow rate of the circulating flow may be uneven, which is not preferable from the viewpoint of homogenizing the molten glass G. Moreover, it is difficult to control the flow rate of the upstream circulating flow 100 and the flow rate of the downstream circulating flow 101 to a specific range described later.
On the other hand, even if the pitch p between individual bubblers is less than 400 mm, it no longer contributes to the promotion of the formation of the circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10. On the contrary, from the viewpoint of cost effectiveness, the number of bubblers 13 provided in the melting tank 10 becomes excessive, which leads to an increase in the manufacturing cost of molten glass, which is not preferable.
　なお、バブラー１３から供給するガス１６には、溶融ガラスＧ、および、バブラー１３等の溶解槽１０Ａの構成要素に悪影響を及ぼさないものを用いることが好ましい。このようなガスの具体例としては、空気、窒素、酸素、ヘリウム、アルゴン等が例示される。バブラー１３の材料として、白金または白金合金が用いられる場合、バブラー１３から供給するガス１６には、窒素、ヘリウム、および、アルゴンといった酸素を含まないガスを用いることが好ましい。これらの中でも窒素が特に好ましい。 In addition, it is preferable to use the gas 16 supplied from the bubbler 13 that does not adversely affect the components of the melting tank 10A such as the molten glass G and the bubbler 13. Specific examples of such a gas include air, nitrogen, oxygen, helium, and argon. When platinum or a platinum alloy is used as the material of the bubbler 13, it is preferable to use a gas that does not contain oxygen, such as nitrogen, helium, and argon, as the gas 16 supplied from the bubbler 13. Of these, nitrogen is particularly preferred.
　本実施形態の溶融ガラス製造方法では、図１，２に示す溶解槽１０Ａでの溶融ガラスＧの流れが、下記（１）～（３）を満たす条件で溶融ガラスを製造する。 In the molten glass manufacturing method of the present embodiment, molten glass is manufactured under the conditions that the flow of the molten glass G in the melting tank 10A shown in FIGS. 1 and 2 satisfies the following (1) to (3).
条件（１）
　バブラー１３よりも上流側に形成される溶融ガラスの上流側循環流１００のうち、溶解槽１０Ａの上流方向に移動する、溶融ガラスの表面付近の流れを、溶融ガラスの上流側表層流１０２とし、溶解槽１０Ａの幅方向における中央付近における、該上流側表層流の平均流速をＶ１Ｃとするとき、Ｖ１Ｃが０ｍ／ｈ超２０ｍ／ｈ以下。
　Ｖ１Ｃを上記範囲とする理由は、ガラス原料中の未溶解物や溶融ガラス表面での揮散等によってできる比重の軽い異質層（スカム層）の前進を抑え、溶融ガラスの均質化を促進するためである。
　本実施形態の溶融ガラス製造方法において、Ｖ１Ｃは、例えば溶融ガラス表層の泡や未融解原料等をカメラで撮影することにより測定できる。
　但し、後述するＶ２Ｃ，Ｖ２Ｓと同様の手順で測定してもよい。 Condition (1)
Of the upstream circulating flow 100 of the molten glass formed upstream of the bubbler 13, the flow in the vicinity of the surface of the molten glass that moves in the upstream direction of the melting tank 10A is defined as the upstream surface flow 102 of the molten glass, When the average flow velocity of the upstream surface layer flow in the vicinity of the center in the width direction of the dissolution tank 10A is V 1C , V 1C is more than 0 m / h and 20 m / h or less.
The reason why V 1C is set in the above range is to suppress the advance of a heterogeneous layer (scum layer) having a light specific gravity caused by undissolved material in the glass raw material or volatilization on the surface of the molten glass, and to promote homogenization of the molten glass. It is.
In the molten glass producing method of the present embodiment, V 1C can be measured, for example by taking molten glass surface of bubbles and unmelted raw materials in the camera.
However, you may measure in the procedure similar to V2C and V2S mentioned later.
　本実施形態の溶融ガラス製造方法において、溶解槽１０Ａでの溶融ガラスの流路方向におけるＶ１Ｃの測定位置、すなわち、上流側表層流をカメラで撮影する位置は、溶融ガラス流路の上流端＋５００ｍｍ～０．３５ＬＦの位置であることが好ましい。この理由は、溶融ガラスの表面付近を溶解槽１０Ａの上流方向に移動する上流側表層流のみを捉えるのに適しているからである。なお、前記Ｖ１Ｃの測定位置は、記載した範囲内での任意の位置を意味する(以下、本明細書において同様。）。 In the molten glass manufacturing method of this embodiment, the measurement position of V 1C in the flow direction of the molten glass in the melting tank 10A, that is, the position where the upstream surface layer flow is photographed with the camera is the upstream end of the molten glass flow channel +500 mm. A position of ~ 0.35L F is preferred. This is because it is suitable for capturing only the upstream surface flow that moves in the upstream direction of the melting tank 10A near the surface of the molten glass. Note that the measurement position of the V 1C means an arbitrary position within the described range (hereinafter, the same applies in this specification).
　本実施形態の溶融ガラス製造方法において、Ｖ１Ｃは、バブラー１３からのガス１６の流量により調節できる。具体的には、バブラー１３からのガス１６の流量を増やすと、Ｖ１Ｃが増加し、ガス１６の流量を減らすと、Ｖ１Ｃが減少する。
　また、Ｖ１Ｃは、バブラー１３の上方の雰囲気温度Ｔ１によっても調節できる。具体的には、バブラー１３の上方の雰囲気温度Ｔ１を高くすると、Ｖ１Ｃが増加し、雰囲気温度Ｔ１を低くすると、Ｖ１Ｃが減少する。 In the molten glass manufacturing method of the present embodiment, V 1C can be adjusted by the flow rate of the gas 16 from the bubbler 13. Specifically, increasing the flow rate of the gas 16 from the bubbler 13 increases V 1C , and decreasing the flow rate of the gas 16 decreases V 1C .
V 1C can also be adjusted by the ambient temperature T 1 above the bubbler 13. Specifically, when the ambient temperature T 1 above the bubbler 13 is increased, V 1C increases, and when the ambient temperature T 1 is decreased, V 1C decreases.
　本実施形態の溶融ガラス製造方法において、バブラー１３からのガス１６の平均流量Ｆが０．５～２０リットル／分であることが好ましく、０．７～５リットル／分であることがより好ましく、０．９～３リットル／分であることがさらに好ましい。 In the molten glass production method of the present embodiment, the average flow rate F of the gas 16 from the bubbler 13 is preferably 0.5 to 20 liters / minute, more preferably 0.7 to 5 liters / minute, More preferably, it is 0.9 to 3 liters / minute.
　本実施形態の溶融ガラス製造方法において、バブラー１３の上方の雰囲気温度Ｔ１及び後述するＴ２は１５９０～１７１０℃であることが好ましく、１６００～１６９５℃であることがより好ましい。
　本明細書における雰囲気温度Ｔ１は、たとえば、バブラー１３の列よりも上流側に直近のバーナーと、該バーナーよりもさらに上流側に位置する直近のバーナーと、の中間位置で測定する。具体的な測定方法としては、たとえば、溶解槽の側面に設けられた観察用窓から、対面側の側面の溶解槽内壁面温度を放射温度計（例えば、ＣＨＩＮＯ　ＩＲ－ＡＨ３ＳＵ（測定波長：０．６５μｍ、ε＝１．０））で測定する（以下の測定においても同様）。 In the molten glass production method of the present embodiment, the atmospheric temperature T 1 above the bubbler 13 and T 2 described later are preferably 1590 to 1710 ° C., more preferably 1600 to 1695 ° C.
Ambient temperatures T 1 herein, for example, the nearest burner upstream of the row of bubblers 13, and the nearest burner located further upstream of the burner, measured at the middle position. As a specific measurement method, for example, from the observation window provided on the side surface of the dissolution tank, the inner wall surface temperature of the facing side surface is measured with a radiation thermometer (for example, CHINO IR-AH3SU (measurement wavelength: 0. 65 μm, ε = 1.0)) (the same applies to the following measurements).
　Ｖ１Ｃを調節する際の雰囲気温度Ｔ１は、バブラー１３の列よりも上流側のバーナー１５による加熱により調節できる。バーナー１５での燃焼は、燃料を酸素ガスと混合して燃焼させたり、燃料を酸素ガスおよび空気と混合して燃焼させたりすることができる。これらの方法を用いることにより、溶融ガラスに水分を含有させることができる。溶解槽１０Ａから下流側の導管２０へと送られた溶融ガラスの後工程において、溶融ガラス中の泡を減圧脱泡により脱泡する場合には、溶融ガラスが水分を含んでいることが好ましいことから、上記のような燃焼が好ましい。 The ambient temperature T 1 when adjusting V 1C can be adjusted by heating with the burner 15 upstream of the row of bubblers 13. Combustion in the burner 15 can be performed by mixing the fuel with oxygen gas and burning it, or mixing the fuel with oxygen gas and air and burning it. By using these methods, moisture can be contained in the molten glass. In the post-process of the molten glass sent from the melting tank 10A to the downstream conduit 20, when the bubbles in the molten glass are defoamed by vacuum degassing, it is preferable that the molten glass contains moisture. Therefore, the combustion as described above is preferable.
条件（２）
（２）バブラー１３よりも下流側に形成される溶融ガラスの下流側循環流１０１のうち、溶解槽１０の下流方向に移動する溶融ガラスの表面付近の流れを、溶融ガラスの下流側表層流１０３とし、溶解槽１０Ａの幅方向における中央付近における、該下流側表層流１０３の平均流速をＶ２Ｃとするとき、Ｖ２Ｃ＝０．１～３０ｍ／ｈ。
条件（３）
　溶解槽１０Ａの幅方向における側部付近における、下流側表層流１０３の平均流速をＶ２Ｓとするとき、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．５。 Condition (2)
(2) Out of the downstream circulating flow 101 of the molten glass formed downstream of the bubbler 13, the flow near the surface of the molten glass moving in the downstream direction of the melting tank 10 is used as the downstream surface layer flow 103 of the molten glass. and then, in the vicinity of the center in the width direction of the melting tank 10A, when the average flow velocity of the downstream side surface current 103 V 2C, V 2C = 0.1 ~ 30m / h.
Condition (3)
When the average flow velocity of the downstream surface layer flow 103 in the vicinity of the side portion in the width direction of the dissolution tank 10A is V 2S , | (V 2C −V 2S ) / V 2C | = 0 to 0.5.
　本願発明者らは、溶解槽１０Ａ内での溶融ガラスＧの流れと、製造されるガラスの品質と、の関係について鋭意検討した結果、下流側循環流１０１のうち、溶融ガラスの表面付近を、溶解槽１０Ａの下流方向に移動する下流側表層流１０３の挙動が、製造されるガラスの品質に大きく影響することを見出した。本願発明者らが得た知見は以下の通り。
（ａ）下流側表層流１０３の流速が高いと、溶解槽１０Ａ内での溶融ガラスの滞留時間が短くなるため、製造されるガラスの品質が低下する。製造されるガラスの品質を向上させるためには、下流側表層流１０３の流速を低くして、溶解槽１０Ａ内での溶融ガラスの滞留時間を増加させる必要がある。
（ｂ）製造後間もない段階の溶解槽１０Ａは、溶解槽１０Ａの側壁による断熱作用が十分発揮されるため、溶解槽１０Ａの幅方向における中央付近と、側部付近と、で、溶融ガラスの温度差はほとんどない。このため、溶解槽１０Ａの幅方向における中央付近と、側部付近と、で、下流側表層流１０３に流速差がつきにくい。
　しかしながら、使用開始から時間が経過すると、溶解槽１０Ａの側壁が溶融ガラスにより侵食されて、その断熱作用が徐々に低下するため、溶解槽１０Ａの幅方向における中央付近と、側部付近と、で、溶融ガラスに温度差が生じるようになる。具体的には、溶解槽１０Ａの幅方向における中央付近に比べて、側部付近の溶融ガラスの温度が低くなる。この結果、溶解槽１０Ａの幅方向における中央付近と、側部付近と、で、下流側表層流１０３に流速差がつくようになる。具体的には、溶解槽１０Ａの幅方向における中央付近に比べて、側部付近の下流側表層流１０３の流速が低くなる。
　溶解槽１０Ａの幅方向における中央付近と、側部付近と、で、下流側表層流１０３の流速の差が大きくなると、製造されるガラスの品質が低下する。 As a result of earnestly examining the relationship between the flow of the molten glass G in the melting tank 10A and the quality of the produced glass, the inventors of the present application, as a result of the downstream circulating flow 101, near the surface of the molten glass, It has been found that the behavior of the downstream surface layer flow 103 moving in the downstream direction of the melting tank 10A greatly affects the quality of the glass to be produced. The knowledge obtained by the present inventors is as follows.
(A) When the flow velocity of the downstream surface layer flow 103 is high, the residence time of the molten glass in the melting tank 10A is shortened, so that the quality of the produced glass is deteriorated. In order to improve the quality of the produced glass, it is necessary to decrease the flow rate of the downstream surface layer flow 103 and increase the residence time of the molten glass in the melting tank 10A.
(B) Since the melting tank 10A at the stage immediately after the production sufficiently exhibits the heat insulating action by the side wall of the melting tank 10A, the molten glass is formed near the center in the width direction of the melting tank 10A and near the side portion. There is almost no temperature difference. For this reason, it is difficult for the downstream surface layer flow 103 to have a flow velocity difference between the vicinity of the center in the width direction of the dissolution tank 10A and the vicinity of the side portion.
However, as time elapses from the start of use, the side wall of the melting tank 10A is eroded by the molten glass, and its heat insulating action gradually decreases, so the vicinity of the center and the side in the width direction of the melting tank 10A As a result, a temperature difference occurs in the molten glass. Specifically, the temperature of the molten glass near the side portion is lower than that near the center in the width direction of the melting tank 10A. As a result, a flow velocity difference is generated in the downstream surface layer flow 103 between the vicinity of the center in the width direction of the dissolution tank 10A and the vicinity of the side portion. Specifically, the flow velocity of the downstream surface layer flow 103 near the side portion is lower than that near the center in the width direction of the dissolution tank 10A.
When the difference in the flow velocity of the downstream surface layer flow 103 between the vicinity of the center in the width direction of the dissolution tank 10A and the vicinity of the side portion becomes large, the quality of the manufactured glass deteriorates.
　条件（２）において、Ｖ２Ｃが３０ｍ／ｈ超だと、溶解槽１０Ａ内での溶融ガラスの滞留時間が短くなるため、製造されるガラスの品質が低下する。このため、３０ｍ／ｈ以下とする。好ましくは１５ｍ／ｈ以下、さらに好ましくは１０ｍ／ｈ以下である。
　但し、Ｖ２Ｃが０．１ｍ／ｈ未満だと、溶融ガラス表面からの揮散が増加し、製造されるガラスの品質が低下する。好ましくは１ｍ／ｈ以上、さらに好ましくは２ｍ／ｈ以上である。 In the condition (2), if V 2C exceeds 30 m / h, the residence time of the molten glass in the melting tank 10A is shortened, so that the quality of the produced glass is deteriorated. For this reason, it shall be 30 m / h or less. Preferably it is 15 m / h or less, More preferably, it is 10 m / h or less.
However, if V2C is less than 0.1 m / h, volatilization from the surface of the molten glass increases, and the quality of the glass to be produced decreases. Preferably it is 1 m / h or more, More preferably, it is 2 m / h or more.
　条件（３）において、溶解槽１０Ａの幅方向における中央付近と、側部付近と、で、下流側表層流１０３の流速差がない場合は、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０となる。これに対し、下流側表層流１０３の流速差が大きくなると、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│の値が大きくなり、０．５超となると、製造されるガラスの品質が低下する。
　なお、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│と、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃの絶対値で規定しているのは、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃが負の数値になる場合、すなわち、溶解槽１０の幅方向における中央付近に比べて、側部付近の下流側表層流１０３の流速が高くなる場合も許容されるからである。
　好ましくは、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．３、より好ましくは、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．１、さらに好ましくは、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．０１である。 In the condition (3), when there is no flow velocity difference between the downstream surface layer flow 103 between the center in the width direction of the dissolution tank 10A and the vicinity of the side portion, | (V 2C −V 2S ) / V 2C | = 0. On the other hand, when the flow velocity difference of the downstream surface layer flow 103 increases, the value of | (V 2C −V 2S ) / V 2C | increases, and when it exceeds 0.5, the quality of the glass to be manufactured decreases. .
The absolute value of | (V 2C −V 2S ) / V 2C | and (V 2C −V 2S ) / V 2C is defined as (V 2C −V 2S ) / V 2C is negative. This is because when the numerical value is reached, that is, when the flow velocity of the downstream surface layer flow 103 near the side portion is higher than that near the center of the dissolution tank 10 in the width direction.
Preferably, │ (V 2C −V 2S ) / V 2C │ = 0 to 0.3, more preferably │ (V 2C −V 2S ) / V 2C │ = 0 to 0.1, and more preferably, (V 2C −V 2S ) / V 2C | = 0 to 0.01.
　本実施形態の溶融ガラス製造方法において、Ｖ２ＣおよびＶ２Ｓは、下流側表層流をカメラで連続的に撮影し、この画像を用いて測定することができる。具体的には、カメラで撮影した画像に対して、背景差分処理することで動的領域を抽出し、これをオプティカルフロー処理し、さらに、幾何補正処理を施して、実空間（三次元）速度を求める。但し、この数値にはある程度ばらつきがあるため、指定した領域において測定された速度の分布より推定される期待値として、Ｖ２ＣおよびＶ２Ｓを求める。 In the molten glass manufacturing method of the present embodiment, V 2C and V 2S can be measured by continuously capturing a downstream surface layer flow with a camera and using this image. Specifically, a dynamic region is extracted by performing background difference processing on an image captured by a camera, this is subjected to optical flow processing, and further subjected to geometric correction processing to obtain a real space (three-dimensional) speed. Ask for. However, since this numerical value varies to some extent, V 2C and V 2S are obtained as expected values estimated from the distribution of speeds measured in the specified region.
　本実施形態の溶融ガラス製造方法において、溶解槽１０Ａでの溶融ガラスの流路方向におけるＶ２ＣおよびＶ２Ｓの測定位置、すなわち、下流側表層流をカメラで撮影する位置は、溶融ガラス流路の上流端から０．６ＬＦ～ＬＦ－５００ｍｍの位置であることが好ましい。この理由は、溶融ガラスの表面付近を溶解槽１０の下流方向に移動する下流側表層流のみを捉えるのに適しているからである。 In the molten glass manufacturing method of the present embodiment, the measurement position of V 2C and V 2S in the molten glass channel direction in the melting tank 10A, that is, the position where the downstream surface layer flow is photographed by the camera is the position of the molten glass channel. The position is preferably 0.6 L F to L F −500 mm from the upstream end. This is because it is suitable for capturing only the downstream surface layer flow that moves in the vicinity of the surface of the molten glass in the downstream direction of the melting tank 10.
　本実施形態の溶融ガラス製造方法において、溶解槽１０Ａの幅方向におけるＶ２Ｃの測定位置は、溶解槽１０Ａの溶融ガラス流路の幅をＷ（ｍｍ）とするとき、２／５Ｗ～３／５Ｗの位置であることが好ましく、９／２０Ｗ～１１／２０Ｗの位置であることがより好ましい。
　一方、溶解槽１０Ａの幅方向におけるＶ２Ｓの測定位置は、０～１／４Ｗの位置であることが好ましい。ここで、０とは、溶解槽１０の側壁近傍、具体的には、側壁から２０ｍｍ以内の位置を指す。
　なお、Ｖ１ＣをＶ２Ｃと同様の手順で測定する場合は、溶解槽１０の幅方向におけるＶ１Ｃの測定位置は、２／５Ｗ～３／５Ｗの位置であることが好ましく、９／２０Ｗ～１１／２０Ｗの位置であることがより好ましい。 In the molten glass manufacturing method of the present embodiment, the measurement position of V 2C in the width direction of the melting tank 10A is 2/5 W to 3/5 W when the width of the molten glass flow path of the melting tank 10A is W (mm). The position is preferably 9/20 W to 11/20 W.
On the other hand, the measurement position of V 2S in the width direction of the dissolution tank 10A is preferably a position of 0 to 1 / 4W. Here, 0 indicates the vicinity of the side wall of the dissolution tank 10, specifically, a position within 20 mm from the side wall.
When V 1C is measured in the same procedure as V 2C , the measurement position of V 1C in the width direction of the dissolution tank 10 is preferably a position of 2 / 5W to 3 / 5W, preferably 9 / 20W to A position of 11/20 W is more preferable.
　本実施形態の溶融ガラス製造方法では、上記の手順でＶ２ＣおよびＶ２Ｓを測定するために、下流側表層流の画像をある程度の範囲で捉える必要がある。
　Ｖ２Ｃを測定する目的では、下流側表層流の画像を捉える範囲は、以下の範囲であることが好ましい。
溶融ガラスの流路方向：１００ｍｍ～３０００ｍｍ、より好ましくは、２００ｍｍ～１０００ｍｍ、さらに好ましくは、３００ｍｍ～５００ｍｍ
溶解槽１０Ａの幅方向：Ｗ／７５～Ｗ／５、より好ましくは、Ｗ／３０～Ｗ／７、さらに好ましくは、Ｗ／１６～Ｗ／１４
　なお、Ｖ１ＣをＶ２Ｃと同様の手順で測定する場合は、上流側表層流の画像を捉える範囲は、上記と同様であることが好ましい。
　Ｖ２Ｓを測定する目的では、下流側表層流の画像を捉える範囲は、以下の範囲であることが好ましい。
溶融ガラスの流路方向：２００ｍｍ～３０００ｍｍ、より好ましくは、３００ｍｍ～１５００ｍｍ、さらに好ましくは、４００ｍｍ～９００ｍｍ
溶解槽１０の幅方向：Ｗ／３０～Ｗ／２、より好ましくは、Ｗ／１０～Ｗ／４、さらに好ましくは、Ｗ／７～Ｗ／５ In the molten glass manufacturing method of the present embodiment, in order to measure V 2C and V 2S by the above procedure, it is necessary to capture an image of the downstream surface layer flow within a certain range.
For the purpose of measuring the V 2C, the range to capture the image of the downstream surface current is preferably in the following ranges.
Flow path direction of molten glass: 100 mm to 3000 mm, more preferably 200 mm to 1000 mm, still more preferably 300 mm to 500 mm
Dissolving tank 10A width direction: W / 75 to W / 5, more preferably W / 30 to W / 7, and still more preferably W / 16 to W / 14
In the case where V 1C is measured in the same procedure as V 2C , it is preferable that the range in which the upstream surface flow image is captured is the same as described above.
For the purpose of measuring the V 2S, range to capture the image of the downstream surface current is preferably in the following ranges.
Flow path direction of molten glass: 200 mm to 3000 mm, more preferably 300 mm to 1500 mm, still more preferably 400 mm to 900 mm
The width direction of the dissolution tank 10: W / 30 to W / 2, more preferably W / 10 to W / 4, still more preferably W / 7 to W / 5
　また、下流側表層流の画像を捉える範囲は、フレームの写りこみによる、激しい明度の変化を伴わない範囲であることが好ましい。 In addition, it is preferable that the range in which an image of the downstream surface layer flow is captured is a range that does not involve a drastic change in brightness due to the reflection of the frame.
　条件（２）におけるＶ２Ｃは、バブラー１３からのガス１６の流量により調節できる。具体的には、バブラー１３からのガス１６の流量を増やすと、Ｖ２Ｃが増加し、ガス１６の流量を減らすと、Ｖ２Ｃが減少する。
　また、Ｖ２Ｃは、バブラー１３の上方の雰囲気温度Ｔ２によっても調節できる。具体的には、バブラー１３の上方の雰囲気温度Ｔ２を高くすると、Ｖ２Ｃが増加し、雰囲気温度Ｔ２を低くすると、Ｖ２Ｃが減少する。
　本実施形態の溶融ガラス製造方法において、バブラー１３からのガス１６の平均流量Ｆの好適範囲、および、バブラー１３の上方の雰囲気温度Ｔ２の好適範囲については上述した通りである。
　Ｖ２Ｃを調節する際の雰囲気温度Ｔ２は、バブラー１３の列と、該バブラーよりも下流側に直近のバーナーと、の中間位置で測定する。
　Ｖ２Ｃを調節する際の雰囲気温度Ｔ２は、バブラー１３の列よりも下流側のバーナー１５による加熱により調節できる。バーナー１５での燃焼については、上述した通りである。 V 2C in the condition (2) can be adjusted by the flow rate of the gas 16 from the bubbler 13. Specifically, when the flow rate of the gas 16 from the bubbler 13 is increased, V 2C increases, and when the flow rate of the gas 16 is decreased, V 2C decreases.
V 2C can also be adjusted by the ambient temperature T 2 above the bubbler 13. Specifically, the higher the upper atmospheric temperature T 2 of the bubbler 13, an increase in V 2C, the lower the ambient temperature T 2, V 2C is reduced.
In the molten glass producing method of the present embodiment, the preferred range of the average flow rate F of the gas 16 from the bubbler 13, and is as described above for the preferred range of ambient temperature T 2 above the bubbler 13.
Ambient temperature T 2 in regulating V 2C includes a row of bubblers 13, and the nearest burner downstream from said bubbler, measured at an intermediate position.
The atmospheric temperature T 2 when adjusting V 2C can be adjusted by heating by the burner 15 on the downstream side of the row of bubblers 13. The combustion in the burner 15 is as described above.
　条件（３）におけるＶ２ＣとＶ２Ｓとの関係は、バブラー１３の列よりも下流側のバーナー１５による加熱により調節できる。
　上述したように、Ｖ２ＣとＶ２Ｓとで差が生じるのは、溶解槽１０Ａの幅方向における中央付近と、側部付近と、で溶融ガラスに温度差が生じること、具体的には、溶解槽１０Ａの幅方向における中央付近に比べて、側部付近の溶融ガラスの温度が低くなるのが原因である。バブラー１３の列よりも下流側のバーナー１５による加熱により、側部付近の溶融ガラスの温度を上昇させて、溶解槽１０Ａの幅方向における中央付近と、側部付近と、の溶融ガラスの温度差を減らすことができる。これにより、Ｖ２ＣとＶ２Ｓとの差が減少し、｜（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ｜の値が小さくなる。 The relationship between V 2C and V 2S in the condition (3) can be adjusted by heating with the burner 15 on the downstream side of the row of bubblers 13.
As described above, the difference between V 2C and V 2S is caused by a temperature difference in the molten glass between the center in the width direction of the melting tank 10A and the vicinity of the side, specifically, melting. This is because the temperature of the molten glass near the side portion is lower than that near the center in the width direction of the tank 10A. The temperature of the molten glass near the side is increased by heating by the burner 15 on the downstream side of the row of bubblers 13, and the temperature difference between the molten glass near the center and the side in the width direction of the melting tank 10A. Can be reduced. As a result, the difference between V 2C and V 2S decreases, and the value of | (V 2C −V 2S ) / V 2C | decreases.
　また、条件（３）におけるＶ２ＣとＶ２Ｓとの関係は、バブラー１３からのガス１６の流量によっても調節できる。具体的には、溶解槽１０Ａの幅方向における中央付近のバブラー１３からのガス１６の流量に対し、側部付近のバブラー１３からのガス１６の流量を大きくすることで、Ｖ２ＣとＶ２Ｓとの差が減少し、｜（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ｜の値が小さくなる。
　なお、溶解槽１０の幅方向における中央付近のバブラー１３からのガス１６の流量に対し、側部付近のバブラー１３からのガス１６の流量を大きくすることにより、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃを負の数値とすること、すなわち、溶解槽１０の幅方向における中央付近に比べて、側部付近の下流側表層流１０３の流速が高くすることも可能である。 Further, the relationship between V 2C and V 2S in the condition (3) can be adjusted by the flow rate of the gas 16 from the bubbler 13. Specifically, by increasing the flow rate of the gas 16 from the bubbler 13 near the side relative to the flow rate of the gas 16 from the bubbler 13 near the center in the width direction of the dissolution tank 10A, V 2C and V 2S And the value of | (V 2C −V 2S ) / V 2C | becomes smaller.
In addition, by increasing the flow rate of the gas 16 from the bubbler 13 near the side with respect to the flow rate of the gas 16 from the bubbler 13 near the center in the width direction of the dissolution tank 10, (V 2C −V 2S ) / V It is also possible to make 2C a negative value, that is, the flow velocity of the downstream surface layer flow 103 near the side portion is higher than that near the center in the width direction of the dissolution tank 10.
　図３は、本発明の溶融ガラス製造方法に用いる溶解槽の別の一実施形態の断面図であり、図４は、図３に示す溶解槽の平面図である。 FIG. 3 is a cross-sectional view of another embodiment of the melting tank used in the molten glass production method of the present invention, and FIG. 4 is a plan view of the melting tank shown in FIG.
　図３、４に示す溶解槽１０Ｂでは、上述した溶解槽１０Ａの複数のバブラー１３の代わりに、溶解槽１０Ｂの溶融ガラス流路方向における位置が互いに異なる、複数の第１のバブラー１３Ａ、および、複数の第２のバブラー１３Ｂが設けられている。第１のバブラー１３Ａは、第２のバブラー１３Ｂよりも溶融ガラス流路の上流側に設けられており、第１のバブラー１３Ａの列と第２のバブラー１３Ｂの列との間には所定の間隔が設けられている。
　なお、第１のバブラー１３Ａ、および、第２のバブラー１３Ｂの列方向における個々のバブラーのピッチについては、上述した溶解槽１０Ａのバブラー１３について記載したのと同様である。第１のバブラー１３Ａの列と第２のバブラー１３Ｂ列との距離の好適範囲については後述する。 In the dissolution tank 10B shown in FIGS. 3 and 4, instead of the plurality of bubblers 13 of the dissolution tank 10A described above, a plurality of first bubblers 13A having different positions in the molten glass flow path direction of the dissolution tank 10B, and A plurality of second bubblers 13B are provided. The first bubbler 13A is provided on the upstream side of the molten glass flow path with respect to the second bubbler 13B, and a predetermined distance is provided between the first bubbler 13A row and the second bubbler 13B row. Is provided.
Note that the pitches of the individual bubblers in the row direction of the first bubbler 13A and the second bubbler 13B are the same as those described for the bubbler 13 of the dissolution tank 10A. A preferable range of the distance between the first bubbler 13A row and the second bubbler 13B row will be described later.
　図３、４に示す溶解槽１０Ｂの両側面には、該溶解槽１０Ｂ内に保持された溶融ガラスＧよりも上方に位置するようにバーナー１５が配置されている。バーナー１５は、後述する例外部分を除いて、溶解槽１０Ｂの長さ方向全体にわたって等間隔で設けられている。 3 and 4, burners 15 are arranged on both sides of the melting tank 10B so as to be positioned above the molten glass G held in the melting tank 10B. The burners 15 are provided at regular intervals throughout the entire length of the dissolution tank 10B, except for exceptions described later.
　図３、４に示す溶解槽１０Ｂは、第１，２のバブラー１３Ａ，１３Ｂ、および、バーナー１５を後述する特定の配置にすることにより、溶融ガラス流路の底部に特許文献１、２に記載されているような溶融ガラス流に影響を与える段差構造を設けることなしに、溶解槽１０Ｂ内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進できる点でより優れている。
　したがって、図１，２に示す溶解槽１０Ａと同様に、Ｔηが１５００～１７６０℃であり、ソーダライムガラス等のアルカリ含有ガラスに比べて１００℃以上高い無アルカリガラスの製造に好適である。 The melting tank 10B shown in FIGS. 3 and 4 is described in Patent Documents 1 and 2 at the bottom of the molten glass flow path by arranging the first and second bubblers 13A and 13B and the burner 15 in a specific arrangement described later. The formation of a circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10B can be promoted without providing a step structure that affects the molten glass flow. It is better in terms.
Accordingly, similarly to the melting tank 10A shown in FIGS. 1 and 2, T η is 1500 to 1760 ° C., which is suitable for the production of alkali-free glass that is 100 ° C. or higher compared to alkali-containing glass such as soda lime glass.
　図３、４に示す溶解槽１０Ｂは、該溶解槽１０Ｂの溶融ガラス流路の長さをＬＦとするとき、溶融ガラス流路の上流端から第１のバブラー１３Ａの列までの距離が、０．４ＬＦ～０．５ＬＦであり、溶融ガラス流路の下流端から第２のバブラー１３Ｂの列までの距離が０．４５ＬＦ～０．５５ＬＦである。
　したがって、溶解槽１０Ａと同様に、特許文献１，２に記載されているような従来の溶解槽（溶融炉）に比べて、溶解槽１０Ｂの長さが短く、溶解槽における下流側循環流を形成する部位の長さも短い。 Dissolving tank 10B shown in FIGS. 3 and 4, when the length of molten glass flow path of the dissolution tank 10B and L F, the distance from the upstream end of the molten glass flow path to the row of first bubbler 13A, a 0.4L F ~ 0.5L F, the distance from the downstream end of the molten glass flow path to the row of the second bubblers 13B is 0.45L F ~ 0.55L F.
Therefore, similarly to the dissolution tank 10A, the length of the dissolution tank 10B is shorter than the conventional dissolution tank (melting furnace) as described in Patent Documents 1 and 2, and the downstream circulating flow in the dissolution tank is reduced. The length of the site to be formed is also short.
　図３、４に示す溶解槽１０Ｂにおいて、溶融ガラス流路の上流端から第１のバブラー１３Ａの列までの距離が０．４３ＬＦ～０．４６ＬＦであることが好ましく、溶融ガラス流路の下流端から第２のバブラー１３Ｂの列までの距離が０．４７ＬＦ～０．５４ＬＦであることが好ましい。 In the melting tank 10B shown in FIGS. 3 and 4, the distance from the upstream end of the molten glass channel to the row of the first bubblers 13A is preferably 0.43L F to 0.46L F. The distance from the downstream end to the row of second bubblers 13B is preferably 0.47L F to 0.54L F.
　図３、４に示す溶解槽１０Ｂにおいて、第１のバブラー１３Ａの列と、第２のバブラー１３Ｂの列との距離をＬPとするとき、ＬPが５００～１０００ｍｍである。ＬPが、上記の範囲を満たしていると、溶解槽１０Ｂ内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進する効果に優れ、かつ、上流側循環流１００の流速、および、下流側循環流１０１の流速を後述する特定の範囲に制御できる。
　ＬPが５００ｍｍ未満だと、第１のバブラー１３Ａの列と、第２のバブラー１３Ｂの列との距離が近すぎるため、溶解槽１０Ｂ内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進する効果に乏しく、かつ、上流側循環流１００の流速、および、下流側循環流１０１の流速を後述する特定の範囲に制御するのが困難である。
　ＬPが１０００ｍｍ超の場合も、第１のバブラー１３Ａの列と、第２のバブラー１３Ｂの列との距離が広すぎるため、溶解槽１０Ｂ内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進する効果に乏しく、かつ、上流側循環流１００の流速、および、下流側循環流１０１の流速を後述する特定の範囲に制御するのが困難である。
　溶解槽１０Ｂにおいて、ＬPが６００～８００ｍｍであることが好ましい。 In the dissolution tank 10B shown in FIGS. 3 and 4, when the distance between the row of the first bubblers 13A and the row of the second bubblers 13B is L P , L P is 500 to 1000 mm. When L P satisfies the above range, it is excellent in the effect of promoting the formation of the circulating flow (upstream circulating flow 100, downstream circulating flow 101) of the molten glass G in the melting tank 10B, and upstream. The flow velocity of the side circulation flow 100 and the flow velocity of the downstream circulation flow 101 can be controlled within a specific range described later.
If L P is less than 500 mm, the distance between the row of the first bubblers 13A and the row of the second bubblers 13B is too close, so that the circulating flow of the molten glass G in the melting tank 10B (upstream circulating flow 100 In addition, the effect of promoting the formation of the downstream circulation flow 101) is poor, and it is difficult to control the flow rate of the upstream circulation flow 100 and the flow rate of the downstream circulation flow 101 to a specific range described later.
Even when L P is greater than 1000 mm, the distance between the row of the first bubblers 13A and the row of the second bubblers 13B is too wide, so that the circulating flow of the molten glass G in the melting tank 10B (upstream circulating flow) 100, the effect of promoting the formation of the downstream circulation flow 101) is poor, and it is difficult to control the flow rate of the upstream circulation flow 100 and the flow rate of the downstream circulation flow 101 to a specific range described later. .
In the dissolution tank 10B, L P is preferably 600 to 800 mm.
　第１のバブラー１３Ａおよび第２のバブラー１３Ｂにおいて、バブラーの列方向における個々のバブラー間のピッチｐについては、溶解槽１０Ａのバブラー１３について記載したのと同様である。 In the first bubbler 13A and the second bubbler 13B, the pitch p between individual bubblers in the row direction of the bubblers is the same as that described for the bubbler 13 of the dissolution tank 10A.
　図３、４に示す溶解槽１０Ｂにおける溶融ガラスの流路方向を軸とするとき、第１のバブラー１３Ａと第２のバブラー１３Ｂとが同軸上に存在しないように配置されていることが好ましい。
　図４に示す溶解槽１０Ｂにおいて、第１のバブラー１３Ａと第２のバブラー１３Ｂとが千鳥状に配置されており、第１のバブラー１３Ａの突出口と第２のバブラー１３Ｂの突出口とが同軸上に存在しない。
　このような配置にした場合、第１のバブラー１３Ａの突出口のいずれかが機能しなくなった場合であっても、下流側に千鳥状に配置された第２のバブラー１３Ｂの突出口の存在により、溶解槽１０Ｂ内での溶融ガラスＧの循環流（上流側循環流１００、下流側循環流１０１）の形成を促進する効果が損なわれることがない。 It is preferable that the first bubbler 13 </ b> A and the second bubbler 13 </ b> B are arranged so as not to be coaxial with respect to the flow direction of the molten glass in the melting tank 10 </ b> B shown in FIGS.
In the dissolution tank 10B shown in FIG. 4, the first bubbler 13A and the second bubbler 13B are arranged in a staggered manner, and the protruding port of the first bubbler 13A and the protruding port of the second bubbler 13B are coaxial. Does not exist above.
In such an arrangement, even if one of the protruding ports of the first bubbler 13A stops functioning, the presence of the protruding ports of the second bubbler 13B arranged in a staggered pattern on the downstream side. The effect of promoting the formation of the circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10B is not impaired.
　なお、第１のバブラー１３Ａおよび第２のバブラー１３Ｂから供給するガス１６Ａ、１６Ｂについては、溶解槽１０Ａのバブラー１３から供給するガス１６について記載したのと同様である。 Note that the gases 16A and 16B supplied from the first bubbler 13A and the second bubbler 13B are the same as described for the gas 16 supplied from the bubbler 13 of the dissolution tank 10A.
　図３、４に示す溶解槽１０Ｂの両側面には、該溶解槽１０Ｂの長さ方向全体にわたってバーナー１５が等間隔で設けられている。但し、第２のバブラー１３Ｂの上方にはバーナー１５が設けられていない。これは、第２のバブラー１３Ｂの上方の雰囲気温度Ｔ２を第１のバブラー１３Ａの上方の雰囲気温度Ｔ１よりも低くするためである。これにより、下流側循環流１０１の単位時間当たりの流量を上流側循環流１００より低くできる。これは、主として、ガラス原料の溶融と清澄を目的とする上流側循環流１００よりも、溶融ガラスの均質化を目的とする下流側循環流１０１のほうが、単位時間当たりの流量を低くすることが好ましいからである。 Burners 15 are provided at equal intervals over the entire length of the dissolution tank 10B on both sides of the dissolution tank 10B shown in FIGS. However, the burner 15 is not provided above the second bubbler 13B. This is to be lower than the ambient temperature T 1 of the upper atmosphere temperature T 2 above the second bubbler 13B first bubbler 13A. Thereby, the flow rate per unit time of the downstream circulation flow 101 can be made lower than that of the upstream circulation flow 100. This is because the flow rate per unit time is lower in the downstream circulation flow 101 for the purpose of homogenizing the molten glass than in the upstream circulation flow 100 for the purpose of melting and clarifying the glass raw material. It is because it is preferable.
　第２のバブラー１３Ｂの上方の雰囲気温度Ｔ２を第１のバブラー１３Ａの上方の雰囲気温度Ｔ１よりも低くするためには、図４に示すように、第２のバブラー１３Ｂの列と該列の下流側に直近のバーナー１５ｎとをある程度離して配置する必要がある。このため、第２のバブラー１３Ｂの列と該列の下流側に直近のバーナー１５との距離ＬＢ２を８００ｍｍ以上とする必要がある。
　但し、第２のバブラー１３Ｂの列と該列の下流側に直近のバーナー１５ｎとを離しすぎると、第２のバブラー１３Ｂの上方の雰囲気温度Ｔ２が低くなりすぎて、却って溶融ガラスの均質化が不十分になる等の問題が生じる。また、溶解槽１０Ｂの下流側の端部１０ｅに設けられた払出し口１２から払出される溶融ガラスＧの温度が低くなり、後工程において減圧脱泡を行う場合に脱泡し難くなる等の問題が生じる。このため、ＬＢ２を２５００ｍｍ以下とする必要がある。
　したがって、ＬＢ２＝８００～２５００ｍｍである。なお、ＬＢ２＝１０００～２０００ｍｍであることが好ましく、ＬＢ２＝１０００～１６００ｍｍであることがより好ましい。 To lower the upper atmospheric temperature T 2 of the second bubbler 13B than the atmosphere above the temperature T 1 of the first bubbler 13A, as shown in FIG. 4, columns of the second bubbler 13B and said column It is necessary to dispose the burner 15n closest to the downstream side of the heater to some extent. For this reason, the distance L B2 between the row of the second bubblers 13B and the burner 15 closest to the downstream side of the row needs to be 800 mm or more.
However, too away and the nearest burner 15n on the downstream side of the column and said column of the second bubbler 13B, ambient temperature T 2 above the second bubbler 13B is too low, rather homogenization of molten glass This causes problems such as insufficient. Moreover, the temperature of the molten glass G discharged | emitted from the discharge port 12 provided in the downstream edge part 10e of the melting tank 10B becomes low, and when depressurization defoaming is performed in a post process, it is difficult to defoam. Occurs. For this reason, L B2 needs to be 2500 mm or less.
Therefore, L B2 = 800 to 2500 mm. Note that L B2 = 1000 to 2000 mm is preferable, and L B2 = 1000 to 1600 mm is more preferable.
　また、第２のバブラー１３Ｂの上方の雰囲気温度Ｔ２を第１のバブラー１３Ａの上方の雰囲気温度Ｔ１よりも低くするためには、図４に示す溶解槽１０Ｂでは、溶解槽１０Ｂでの溶融ガラスの流路方向における、第１のバブラー１３Ａの列と該列の上流側に直近のバーナー１５との距離ＬＢ１と、第２のバブラー１３Ｂの列と該列の下流側に直近のバーナー１５との距離ＬＢ２と、が、ＬＢ２＞ＬＢ１の関係になることが必要である。すなわち、第１のバブラー１３Ａの上方にバーナー１５が設けられているのに対して、第２のバブラー１３Ｂの上方にはバーナー１５が設けない。図４に示す溶解槽１０Ｂでは、このような配置とすることによって、第２のバブラーの上方の雰囲気温度Ｔ２を第１のバブラーの上方の雰囲気温度Ｔ１よりも低くすることができる。
　本実施形態において、ＬＢ２－ＬＢ１≧３００ｍｍであることが好ましく、ＬＢ２－ＬＢ１≧５００ｍｍであることがより好ましく、ＬＢ２－ＬＢ１≧８００ｍｍであることがさらに好ましい。 Further, in order to lower the upper atmospheric temperature T 2 of the second bubbler 13B than the atmosphere above the temperature T 1 of the first bubbler 13A is the dissolving tank 10B shown in FIG. 4, the melt in the melting tank 10B The distance L B1 between the row of first bubblers 13A and the burner 15 closest to the upstream side of the row in the glass flow path direction, and the burner 15 nearest to the row of second bubblers 13B and the downstream side of the row It is necessary that the distance L B2 to be in a relationship of L B2 > L B1 . That is, the burner 15 is provided above the first bubbler 13A, whereas the burner 15 is not provided above the second bubbler 13B. In dissolving tank 10B shown in FIG. 4, by this arrangement, it can be made lower than the ambient temperature T 1 of the upper atmosphere temperature T 2 above the second bubbler first bubbler.
In the present embodiment, L B2 −L B1 ≧ 300 mm is preferable, L B2 −L B1 ≧ 500 mm is more preferable, and L B2 −L B1 ≧ 800 mm is further preferable.
　一方、図４に示す溶解槽１０Ｂでは、第１のバブラー１３Ａの列の上方にバーナー１５が設けられているが、ＬＢ２＞ＬＢ１の関係を満たす限り、第１のバブラー１３Ａの列と該列の上流側に直近のバーナー１５とをある程度離して配置してもよい。但し、第１のバブラー１３Ａの列と該列の上流側に直近のバーナー１５とを離しすぎると、第１のバブラー１３Ａの上方の雰囲気温度が低くなりすぎて上流側循環流１００が弱まり、ガラス原料の溶解が不十分になる、また、それにより、溶解槽１０の下流域での溶融ガラスＧの均質化が不十分になる等の問題が生じる。このため、ＬＢ１＝２０００ｍｍ以下とする必要がある。
　したがって、ＬＢ１＝０～２０００ｍｍである。なお、ＬＢ１＝５００～１５００ｍｍであることが好ましい。
　なお、隣り合うバーナー１５間のピッチについては、図２に示す溶解槽１０Ａについて記載したのと同様である。 On the other hand, in the dissolution tank 10B shown in FIG. 4, the burner 15 is provided above the row of the first bubblers 13A. However, as long as the relationship of L B2 > L B1 is satisfied, the row of the first bubblers 13A The nearest burner 15 may be arranged some distance away from the upstream side of the row. However, if the row of the first bubblers 13A and the burner 15 closest to the upstream side of the row are separated too much, the ambient temperature above the first bubbler 13A becomes too low and the upstream circulation flow 100 becomes weak, and the glass Problems such as insufficient melting of the raw materials and insufficient homogenization of the molten glass G in the downstream region of the melting tank 10 occur. For this reason, it is necessary to set L B1 = 2000 mm or less.
Therefore, L B1 = 0 to 2000 mm. Note that L B1 = 500 to 1500 mm is preferable.
In addition, about the pitch between the adjacent burners 15, it is the same as having described about the dissolution tank 10A shown in FIG.
　本実施形態の溶融ガラス製造方法において、図３、４に示す溶解槽１０Ｂでの溶融ガラスＧの流れが、下記（１）～（３）を満たす条件で溶融ガラスを製造する。 In the molten glass manufacturing method of the present embodiment, molten glass is manufactured under the condition that the flow of the molten glass G in the melting tank 10B shown in FIGS. 3 and 4 satisfies the following (1) to (3).
条件（１）
　第１のバブラー１３Ａよりも上流側に形成される溶融ガラスの上流側循環流１００のうち、溶解槽１０Ｂの上流方向に移動する、溶融ガラスの表面付近の流れを、溶融ガラスの上流側表層流１０２とし、溶解槽１０Ｂの幅方向における中央付近における、該上流側表層流の平均流速をＶ１Ｃとするとき、Ｖ１Ｃが０ｍ／ｈ超２０ｍ／ｈ以下。
　Ｖ１Ｃを上記範囲とする理由は、ガラス原料中の未溶解物や溶融ガラス表面での揮散等によってできる比重の軽い異質層（スカム層）の前進を抑え、溶融ガラスの均質化を促進するためである。
　Ｖ１Ｃの測定方法、および、測定位置については、溶解槽１０Ａについて記載したのと同様である。 Condition (1)
Among the upstream circulating flow 100 of the molten glass formed upstream of the first bubbler 13A, the flow near the surface of the molten glass that moves in the upstream direction of the melting tank 10B is the upstream surface flow of the molten glass. and 102, in the vicinity of the center in the width direction of the melting tank 10B, when the average flow velocity of the upstream side surface current and V 1C, V 1C is less 0 m / h super 20 m / h.
The reason why V 1C is set in the above range is to suppress the advance of a heterogeneous layer (scum layer) having a light specific gravity caused by undissolved material in the glass raw material or volatilization on the surface of the molten glass, and to promote homogenization of the molten glass. It is.
About the measuring method of V1C and a measurement position, it is the same as having described about 10 A of dissolution tanks.
　本実施形態の溶融ガラス製造方法において、Ｖ１Ｃは、第１のバブラー１３Ａからのガス１６Ａの流量により調節できる。具体的には、第１のバブラー１３Ａからのガス１６Ａの流量を増やすと、Ｖ１Ｃが増加し、ガス１６Ａの流量を減らすと、Ｖ１Ｃが減少する。
　また、Ｖ１Ｃは、第１のバブラー１３Ａの上方の雰囲気温度Ｔ１によっても調節できる。具体的には、第１のバブラー１３Ａの上方の雰囲気温度Ｔ１を高くすると、Ｖ１Ｃが増加し、雰囲気温度Ｔ１を低くすると、Ｖ１Ｃが減少する。 In the molten glass manufacturing method of the present embodiment, V 1C can be adjusted by the flow rate of the gas 16A from the first bubbler 13A. Specifically, when the flow rate of the gas 16A from the first bubbler 13A is increased, V 1C increases, and when the flow rate of the gas 16A is decreased, V 1C decreases.
V 1C can also be adjusted by the ambient temperature T 1 above the first bubbler 13A. Specifically, the higher the ambient temperature T 1 of the upper first bubbler 13A, increased V 1C, the lower the ambient temperatures T 1, V 1C is reduced.
　本実施形態の溶融ガラス製造方法において、第１のバブラー１３Ａからのガス１６Ａの平均流量Ｆ１が０．５～２０リットル／分であることが好ましく、０．７～５リットル／分であることがより好ましく、０．９～３リットル／分であることがさらに好ましい。 In the molten glass producing method of the present embodiment, it is preferable that the average flow rate F 1 of the gas 16A from the first bubbler 13A is 0.5 to 20 l / min, is from 0.7 to 5 l / min Is more preferably 0.9 to 3 liters / minute.
　本実施形態の溶融ガラス製造方法において、第１のバブラー１３Ａの上方の雰囲気温度Ｔ１は１５９０～１７１０℃であることが好ましく、１６００～１６９５℃であることがより好ましい。
　本明細書における雰囲気温度Ｔ１は、たとえば、第１のバブラー１３Ａの列よりも上流側に直近のバーナーと、該バーナーよりもさらに上流側に位置する直近のバーナーと、の中間位置で測定する。具体的な測定方法については、溶解槽１０Ａの雰囲気温度Ｔ１について記載したのと同様である。 In the molten glass manufacturing method of the present embodiment, the atmospheric temperature T 1 above the first bubbler 13A is preferably 1590 to 1710 ° C., more preferably 1600 to 1695 ° C.
The ambient temperature T 1 in this specification is measured at an intermediate position between, for example, the burner closest to the upstream side of the row of the first bubblers 13A and the burner closest to the upstream side of the burner. . A specific measurement method is as described for the atmospheric temperature T 1 of the melting tank 10A.
　雰囲気温度Ｔ１は、第１のバブラー１３Ａの列よりも上流側のバーナー１５による加熱により調節できる。バーナー１５での燃焼については、溶解槽１０Ａについて記載したのと同様である。 Ambient temperatures T 1 may be adjusted by heating by the upstream side of the burner 15 than the row of the first bubbler 13A. The combustion in the burner 15 is the same as that described for the dissolution tank 10A.
条件（２）
（２）第２のバブラー１３Ｂよりも下流側に形成される溶融ガラスの下流側循環流１０１のうち、溶解槽１０Ｂの下流方向に移動する溶融ガラスの表面付近の流れを、溶融ガラスの下流側表層流１０３とし、溶解槽１０Ｂの幅方向における中央付近における、該下流側表層流１０３の平均流速をＶ２Ｃとするとき、Ｖ２Ｃ＝０．１～３０ｍ／ｈ。
条件（３）
　溶解槽１０Ｂの幅方向における側部付近における、下流側表層流１０３の平均流速をＶ２Ｓとするとき、｜（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ｜＝０～０．５。 Condition (2)
(2) Of the downstream circulating flow 101 of the molten glass formed on the downstream side of the second bubbler 13B, the flow in the vicinity of the surface of the molten glass moving in the downstream direction of the melting tank 10B is the downstream side of the molten glass. When the average flow velocity of the downstream surface layer flow 103 in the vicinity of the center in the width direction of the dissolution tank 10B is V 2C , V 2C = 0.1 to 30 m / h.
Condition (3)
When the average flow velocity of the downstream surface layer flow 103 in the vicinity of the side portion in the width direction of the dissolution tank 10B is V 2S , | (V 2C −V 2S ) / V 2C | = 0 to 0.5.
　条件（２）において、Ｖ２Ｃが３０ｍ／ｈ超だと、溶解槽１０Ｂ内での溶融ガラスの滞留時間が短くなるため、製造されるガラスの品質が低下する。このため、３０ｍ／ｈ以下とする。好ましくは１５ｍ／ｈ以下、さらに好ましくは１０ｍ／ｈ以下である。
　但し、Ｖ２Ｃが０．１ｍ／ｈ未満だと、溶融ガラス表面からの揮散が増加し、製造されるガラスの品質が低下する。好ましくは１ｍ／ｈ以上、さらに好ましくは２ｍ／ｈ以上である。 In the condition (2), if V 2C exceeds 30 m / h, the residence time of the molten glass in the melting tank 10B is shortened, so that the quality of the produced glass is deteriorated. For this reason, it shall be 30 m / h or less. Preferably it is 15 m / h or less, More preferably, it is 10 m / h or less.
However, if V2C is less than 0.1 m / h, volatilization from the surface of the molten glass increases, and the quality of the glass to be produced decreases. Preferably it is 1 m / h or more, More preferably, it is 2 m / h or more.
　条件（３）において、溶解槽１０Ｂの幅方向における中央付近と、側部付近と、で、下流側表層流１０３の流速差がない場合は、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０となる。これに対し、下流側表層流１０３の流速差が大きくなると、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│の値が大きくなり、０．５超となると、製造されるガラスの品質が低下する。
　好ましくは、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２│Ｃ＝０～０．３、より好ましくは、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．１、さらに好ましくは、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．０１である。 In the condition (3), when there is no flow velocity difference of the downstream surface layer flow 103 between the center and the side in the width direction of the dissolution tank 10B, | (V 2C −V 2S ) / V 2C | = 0. On the other hand, when the flow velocity difference of the downstream surface layer flow 103 increases, the value of | (V 2C −V 2S ) / V 2C | increases, and when it exceeds 0.5, the quality of the glass to be manufactured decreases. .
Preferably, │ (V 2C -V 2S) / V 2 │ C = 0 ~ 0.3, more preferably, │ (V 2C -V 2S) / V 2C │ = 0 ~ 0.1, more preferably, │ (V 2C -V 2S ) / V 2C │ = 0 to 0.01.
　Ｖ２ＣおよびＶ２Ｓの測定方法、および、測定位置については、溶解槽１０Ａについて記載したのと同様である。 About the measuring method of V2C and V2S , and the measurement position, it is the same as having described about dissolution tank 10A.
　条件（２）におけるＶ２Ｃは、第２のバブラー１３Ｂからのガス１６Ｂの流量により調節できる。具体的には、第２のバブラー１３Ｂからのガス１６Ｂの流量を増やすと、Ｖ２Ｃが増加し、ガス１６Ｂの流量を減らすと、Ｖ２Ｃが減少する。
　また、Ｖ２Ｃは、第２のバブラー１３Ｂの上方の雰囲気温度Ｔ２によっても調節できる。具体的には、第２のバブラー１３Ｂの上方の雰囲気温度Ｔ２を高くすると、Ｖ２Ｃが増加し、雰囲気温度Ｔ２を低くすると、Ｖ２Ｃが減少する。 V 2C in the condition (2) can be adjusted by the flow rate of the gas 16B from the second bubbler 13B. Specifically, when the flow rate of the gas 16B from the second bubbler 13B is increased, V 2C increases, and when the flow rate of the gas 16B is decreased, V 2C decreases.
V 2C can also be adjusted by the ambient temperature T 2 above the second bubbler 13B. Specifically, the higher the upper atmospheric temperature T 2 of the second bubbler 13B, increased V 2C, the lower the ambient temperature T 2, V 2C is reduced.
　本実施形態の溶融ガラス製造方法において、第２のバブラー１３Ｂからのガス１６Ｂの平均流量Ｆ２が０．３～１９．８リットル／分であることが好ましく、０．４～４．８リットル／分であることがより好ましく、０．５～２リットル／分であることがさらに好ましい。 In the molten glass production method of the present embodiment, the average flow rate F 2 of the gas 16B from the second bubbler 13B is preferably 0.3 to 19.8 liters / minute, preferably 0.4 to 4.8 liters / minute. More preferably, it is 0.5 to 2 liters / minute.
　本実施形態の溶融ガラス製造方法において、第２のバブラー１３Ｂの上方の雰囲気温度Ｔ２は１５９０～１７１０℃であることが好ましく、１６００～１６９５℃であることがより好ましい。
　本明細書における雰囲気温度Ｔ２は、たとえば、第２のバブラー１３Ｂの列と、該バブラーよりも下流側に直近のバーナーと、の中間位置で測定する。 In the molten glass producing method of the present embodiment, it is preferred that ambient temperature T 2 above the second bubbler 13B is 1590 ~ 1710 ° C., and more preferably 1600 ~ 1695 ° C..
Ambient temperature T 2 in the present specification, for example, a column of the second bubbler 13B, the nearest burner downstream from said bubbler, measured at an intermediate position.
　雰囲気温度Ｔ２は、第２のバブラー１３Ｂの列よりも下流側のバーナー１５による加熱により調節できる。バーナー１５での燃焼については、上述した通りである。 Ambient temperature T 2 can be adjusted by heating by a burner 15 on the downstream side of the row of the second bubblers 13B. The combustion in the burner 15 is as described above.
　条件（３）におけるＶ２ＣとＶ２Ｓとの関係は、第２のバブラー１３Ｂの列よりも下流側のバーナー１５による加熱により調節できる。具体的には、第２のバブラー１３Ｂの列よりも下流側のバーナー１５による加熱により、側部付近の溶融ガラスの温度を上昇させて、溶解槽１０Ｂの幅方向における中央付近と、側部付近と、の溶融ガラスの温度差を減らすことができる。これにより、Ｖ２ＣとＶ２Ｓとの差が減少し、｜（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ｜の値が小さくなる。 The relationship between V 2C and V 2S in condition (3) can be adjusted by heating by the burner 15 on the downstream side of the second bubbler 13B row. Specifically, the temperature of the molten glass near the side is raised by heating by the burner 15 downstream from the row of second bubblers 13B, and the vicinity of the center in the width direction of the melting tank 10B and the vicinity of the side The temperature difference of the molten glass can be reduced. As a result, the difference between V 2C and V 2S decreases, and the value of | (V 2C −V 2S ) / V 2C | decreases.
　また、条件（３）におけるＶ２ＣとＶ２Ｓとの関係は、第２のバブラー１３Ｂからのガス１６Ｂの流量によっても調節できる。具体的には、溶解槽１０Ｂの幅方向における中央付近の第２のバブラー１３Ｂからのガス１６Ｂの流量に対し、側部付近の第２のバブラー１３Ｂからのガス１６Ｂの流量を大きくすることで、Ｖ２ＣとＶ２Ｓとの差が減少し、｜（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ｜の値が小さくなる。 Further, the relationship between V 2C and V 2S in the condition (3) can be adjusted by the flow rate of the gas 16B from the second bubbler 13B. Specifically, by increasing the flow rate of the gas 16B from the second bubbler 13B near the side portion relative to the flow rate of the gas 16B from the second bubbler 13B near the center in the width direction of the dissolution tank 10B, The difference between V 2C and V 2S decreases, and the value of | (V 2C −V 2S ) / V 2C | decreases.
　本発明の溶融ガラス製造方法に用いる溶解槽についてさらに記載する。
　溶解槽１０Ａ、１０Ｂの溶融ガラスＧを接する部分の構成材料は、耐熱性および溶融ガラスに対する耐食性に優れていることが求められることからＺｒＯ２含有の耐火レンガが用いられるが、溶融ガラス流路をなす溶解槽１０Ａ、１０Ｂの底面のうち、バブラー１３、第１のバブラー１３Ａの列から上流側に０．１ＬＦ～０．３ＬＦの部分には、質量％でＺｒＯ２が８５％以上９７％以下で、残部がＳｉＯ２を主体とするガラス質の熱溶融耐火物が用いることが好ましい。溶解槽を流通する溶融ガラスの温度は、下流側よりも上流側のほうが高く、また、溶解槽１０Ｂの場合、第２のバブラー１３Ｂからの流量よりも第１のバブラー１３Ａからの流量のほうが大きいため、耐火レンガが侵食されやすいからである。この場合、個々の熱溶融耐火物の厚さは５０～１２０ｍｍであることが好ましく、熱溶融耐火物は２～３個積層させることが好ましい。さらに、このようにして形成した熱溶融耐火物の層の外側に、他のＺｒＯ２含有の耐火レンガを２～５層積層させることができる。なお、溶解槽の溶融ガラスＧと接する部分の全てを上記組成の熱溶融耐火物で構成することが好ましい。また、各耐火レンガをアルミナ・ジルコン質等のタンプ材を介して積層することができる。 It further describes about the dissolution tank used for the molten glass manufacturing method of this invention.
The constituent material of the melting tanks 10A and 10B that contact the molten glass G is required to be excellent in heat resistance and corrosion resistance to the molten glass, and thus a refractory brick containing ZrO 2 is used. Among the bottom surfaces of the melting tanks 10A and 10B, the portion of 0.1L F to 0.3L F upstream from the row of the bubblers 13 and the first bubblers 13A has a ZrO 2 content of 85% or more and 97% by mass. In the following, it is preferable to use a glassy hot-melt refractory mainly composed of SiO 2 in the balance. The temperature of the molten glass flowing through the melting tank is higher on the upstream side than on the downstream side, and in the case of the melting tank 10B, the flow rate from the first bubbler 13A is higher than the flow rate from the second bubbler 13B. This is because the refractory brick is easily eroded. In this case, the thickness of each hot-melt refractory is preferably 50 to 120 mm, and two to three hot-melt refractories are preferably laminated. Further, 2 to 5 layers of other refractory bricks containing ZrO 2 can be laminated on the outside of the layer of the hot-melt refractory thus formed. In addition, it is preferable to comprise all the parts which contact | connect the molten glass G of a melting tank with the hot-melt refractory material of the said composition. Moreover, each refractory brick can be laminated | stacked via stamp materials, such as an alumina zircon material.
　次に、本発明の板ガラス製造方法について説明する。
　本発明の板ガラス製造方法では、上記した本発明の溶融ガラス製造方法により得られた溶融ガラスを板ガラスに成形する。溶融ガラスを成形して板ガラスとする手段としては、フロート法、ダウンドロー法等の各種成形方法を用いることができる。Ｔηが１５００～１７６０℃のガラスの場合、フロート法が特に好ましい。
　本発明の板ガラス製造方法において、上記した本発明の溶融ガラス製造方法により得られた溶融ガラスを板ガラスに成形する前に、該溶融ガラス中の泡を減圧脱泡により脱泡してもよい。
　本発明の板ガラス製造方法では、本発明の溶融ガラス製造方法により得られた均質性が高い溶融ガラスを成形して板ガラスとするので、均質性が高く、透明性が高い板ガラスを得ることができる。
　本発明の板ガラス製造装置では、様々な用途の板ガラスの製造に適用可能であるが、均質性が高く、透明性が高い板ガラスが得られることから、ＦＰＤ用のガラス基板のように、均質性についての要求がきわめて厳しい用途の板ガラスの製造に適用することが特に好ましい。 Next, the plate glass manufacturing method of the present invention will be described.
In the plate glass manufacturing method of the present invention, the molten glass obtained by the above-described molten glass manufacturing method of the present invention is formed into a plate glass. As a means for forming molten glass into plate glass, various forming methods such as a float method and a downdraw method can be used. In the case of a glass having a T η of 1500 to 1760 ° C., the float method is particularly preferable.
In the plate glass manufacturing method of the present invention, before the molten glass obtained by the above-described molten glass manufacturing method of the present invention is formed into plate glass, bubbles in the molten glass may be degassed by vacuum degassing.
In the plate glass manufacturing method of the present invention, since the molten glass having high homogeneity obtained by the molten glass manufacturing method of the present invention is formed into a plate glass, a plate glass having high homogeneity and high transparency can be obtained.
The plate glass production apparatus of the present invention can be applied to the production of plate glass for various uses. However, since a plate glass having high homogeneity and high transparency can be obtained, the homogeneity of the glass substrate for FPD can be obtained. It is particularly preferable to apply it to the production of plate glass for applications in which the demands of these are extremely strict.
　図３、４に示す溶解槽１０Ｂの投入口に所望の組成となるようにガラス原料を投入して、Ｔηが１５００～１７６０℃の無アルカリガラスを製造する。図３、４に示す溶解槽１０Ｂの各部の寸法は以下の通り。
溶融ガラス流路の長さＬＦ：１６～２５ｍ
溶融ガラス流路の幅：５．５～９ｍ
溶融ガラス流路の上流端から第１のバブラー１３Ａの列までの距離
　　：０．４３ＬＦ～０．４６ＬＦ
溶融ガラス流路の下流端から第２のバブラー１３Ｂの列までの距離
　　：０．４７ＬＦ～０．５４ＬＦ
第１のバブラー１３Ａの列と、第２のバブラー１３Ｂの列との距離ＬP：６００～８００ｍｍ
バブラーの列方向における個々のバブラー１３Ａ、１３Ｂのピッチｐ：４００～７００ｍｍ
溶解槽での溶融ガラスの流路方向における、第１のバブラー１３Ａの列と該列の上流側に直近のバーナー１５との距離ＬＢ１：５００～１５００ｍｍ
溶解槽での溶融ガラスの流路方向における、第２のバブラー１３Ｂの列と該列の下流側に直近のバーナー１５との距離ＬＢ２：１０００～２０００ｍｍ
ＬＢ２－ＬＢ１≧５００ｍｍ
溶解槽での溶融ガラスの流路方向における、個々のバーナー間の距離
　　：８００～２４００ｍｍ
　溶解槽の幅方向における中央付近における上流側表層流Ｖ１Ｃを０ｍ／ｈ超２０ｍ／ｈ以下に調整した。
　また、溶解槽の幅方向における中央付近における下流側表層流の平均流速Ｖ２Ｃを、Ｖ２Ｃ＝０．１～３０ｍ／ｈに調整した。
　溶解槽の幅方向における中央付近における下流側表層流の平均流速Ｖ２Ｃと、溶解槽の幅方向における側部付近における下流側表層流の平均流速Ｖ２Ｓと、の関係式（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃが、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＜０．０５の場合と、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＞０．５の場合について、溶融ガラス中の泡数と、測定データ数の比率と、の関係を図５に示した。図５の横軸は、溶融ガラス中の所定の泡数を１とした時の指数であり、縦軸は測定データ数の比率である。なお、溶融ガラス中の泡数は、溶解槽１０の下流側の端部１０ｅに設けられた払出し口１２に連通する導管２０に対して鉛直方向に連結されているドレイン管（図示せず）から、流下中の溶融ガラスをサンプルとして採取して測定した。具体的には、以下の通り。
　電子カメラを備えた検査装置で、溶融ガラスを所定の撮像間隔（３５ｍｓｅｃ）で間欠的に撮像し、撮像した画像を二値化処理して、溶融ガラス中の泡画像を白画像として検出した。検査装置に内蔵された演算部で、欠点画像である白画像の個数を欠点の個数として計数する。さらに泡の移動量を算出し、ドレイン管から流下する単位時間当たりの流量を算出することで、泡の個数は単位溶融ガラスの流下量当りの個数として算出した。
　また、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＜０．１の場合と、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＞０．５の場合；（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＜０．３の場合と、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＞０．５の場合；（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＜０．５の場合と、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＞０．５の場合についても同様に評価した。結果を図６、図７、図８にそれぞれ示す。
　これらの図から明らかなように、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＞０．５の場合に比べて、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＜０．５とすることで、溶融ガラス中の泡数を低減でき、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ＜０．５の範囲で、（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃの値を適宜選択することで、溶融ガラス中の泡数をさらに低減できた。 Glass raw materials are introduced into the inlet of the melting tank 10B shown in FIGS. 3 and 4 so as to have a desired composition, and alkali-free glass having T η of 1500 to 1760 ° C. is manufactured. The dimensions of each part of the dissolution tank 10B shown in FIGS. 3 and 4 are as follows.
Molten glass flow path length L F : 16 to 25 m
Molten glass channel width: 5.5-9m
Distance from the upstream end of the molten glass flow path to the first bubbler 13A row: 0.43L F to 0.46L F
Distance from the downstream end of the molten glass flow path to the row of second bubblers 13B: 0.47L F to 0.54L F
Distance L P between first row of bubblers 13A and second row of bubblers 13B: 600 to 800 mm
Pitch p of individual bubblers 13A and 13B in the row direction of the bubblers: 400 to 700 mm
Distance L B1 between the row of first bubblers 13A and the burner 15 closest to the upstream side of the row in the flow direction of the molten glass in the melting tank: 500 to 1500 mm
Distance L B2 between the row of second bubblers 13B and the burner 15 closest to the downstream side of the row in the flow direction of the molten glass in the melting tank: 1000 to 2000 mm
L B2 -L B1 ≧ 500mm
Distance between individual burners in the flow direction of the molten glass in the melting tank: 800 to 2400 mm
The upstream surface flow V 1C in the vicinity of the center in the width direction of the dissolution tank was adjusted to more than 0 m / h and 20 m / h or less.
Further, the average flow velocity V 2C of the downstream surface layer flow near the center in the width direction of the dissolution tank was adjusted to V 2C = 0.1 to 30 m / h.
A relational expression (V 2C −V 2S) between the average flow velocity V 2C of the downstream surface layer flow near the center in the width direction of the dissolution tank and the average flow velocity V 2S of the downstream surface layer flow near the side portion in the width direction of the dissolution tank. ) / V 2C for (V 2C −V 2S ) / V 2C <0.05 and (V 2C −V 2S ) / V 2C > 0.5, the number of bubbles in the molten glass, The relationship with the ratio of the number of measurement data is shown in FIG. The horizontal axis of FIG. 5 is an index when the predetermined number of bubbles in the molten glass is 1, and the vertical axis is the ratio of the number of measurement data. The number of bubbles in the molten glass is from a drain pipe (not shown) connected in the vertical direction with respect to the conduit 20 communicating with the discharge port 12 provided at the downstream end portion 10e of the melting tank 10. The molten glass under flow was collected as a sample and measured. Specifically:
The molten glass was imaged intermittently at a predetermined imaging interval (35 msec) with an inspection device equipped with an electronic camera, and the captured image was binarized to detect a bubble image in the molten glass as a white image. The number of white images, which are defect images, is counted as the number of defects by a calculation unit built in the inspection apparatus. Further, by calculating the amount of movement of bubbles and calculating the flow rate per unit time flowing down from the drain pipe, the number of bubbles was calculated as the number per unit molten glass flowing down.
Also, when (V 2C −V 2S ) / V 2C <0.1 and (V 2C −V 2S ) / V 2C >0.5; (V 2C −V 2S ) / V 2C <0. 3 and (V 2C −V 2S ) / V 2C >0.5; (V 2C −V 2S ) / V 2C <0.5 and (V 2C −V 2S ) / V 2C The case of> 0.5 was evaluated in the same manner. The results are shown in FIGS. 6, 7, and 8, respectively.
As is clear from these figures, when (V 2C −V 2S ) / V 2C <0.5, compared with the case of (V 2C −V 2S ) / V 2C > 0.5, the molten glass In the range of (V 2C -V 2S ) / V 2C <0.5, the value of (V 2C -V 2S ) / V 2C is appropriately selected, so that the bubbles in the molten glass The number could be further reduced.
　本発明を詳細に、また特定の実施態様を参照して説明したが、本発明の精神と範囲を逸脱することなく、様々な変更や修正を加えることができることは、当業者にとって明らかである。
　本出願は、２０１３年９月６日出願の日本特許出願２０１３－１８４７０５に基づくものであり、その内容はここに参照として取り込まれる。 Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2013-184705 filed on September 6, 2013, the contents of which are incorporated herein by reference.
　　１０Ａ、１０Ｂ：溶解槽
　　１０ｅ：下流側の端部
　　１１：投入口
　　１２：払出し口
　　１３：バブラー
　　１３Ａ：第１のバブラー
　　１３Ｂ：第２のバブラー
　　１５：バーナー
　　１５ｎ：第２のバブラーの列の下流側に直近のバーナー
　　１６：バブラーからのガス
　　１６Ａ：第１のバブラーからのガス
　　１６Ｂ：第２のバブラーからのガス
　　２０：導管
　　１００：上流側循環流
　　１０１：下流側循環流
　　１０２：上流側表層流
　　１０３：下流側表層流 10A, 10B: Dissolution tank 10e: Downstream end 11: Input port 12: Discharge port 13: Bubbler 13A: First bubbler 13B: Second bubbler 15: Burner 15n: Downstream side of the second bubbler row 16: Gas from the bubbler 16A: Gas from the second bubbler 16B: Gas from the second bubbler 20: Pipe 100: Upstream circulation flow 101: Downstream circulation flow 102: Upstream surface flow 103 : Downstream flow

Claims (5)

  1. 　ガラス原料を溶解するための溶解槽を有する溶融ガラス製造装置を用いて溶融ガラスを製造する溶融ガラス製造方法であって、
    　前記溶解槽は、該溶解槽の上部空間を加熱するためのバーナーを有し、
    　該溶解槽底面近傍に、溶融ガラス流路の幅方向にわたって複数のバブラーを有し、
    　前記溶解槽の溶融ガラス流路の長さをＬＦとするとき、前記溶融ガラス流路の上流端から前記複数のバブラーの列までの距離が０．４ＬＦ～０．５５ＬＦであり
    　前記溶解槽での溶融ガラスの流れが、下記（１）～（３）を満たす条件で溶融ガラスを製造することを特徴とする溶融ガラス製造方法。
    （１）前記複数のバブラーよりも上流側に形成される溶融ガラスの上流側循環流のうち、前記溶解槽の上流方向に移動する、溶融ガラスの表面付近の流れを、溶融ガラスの上流側表層流とし、前記溶解槽の幅方向における中央付近における、該上流側表層流の平均流速をＶ１Ｃとするとき、Ｖ１Ｃが０ｍ／ｈ超２０ｍ／ｈ以下。
    （２）前記複数のバブラーよりも下流側に形成される溶融ガラスの下流側循環流のうち、前記溶解槽の下流方向に移動する、溶融ガラスの表面付近の流れを、溶融ガラスの下流側表層流とし、前記溶解槽の幅方向における中央付近における、該下流側表層流の平均流速をＶ２Ｃとするとき、Ｖ２Ｃ＝０．１～３０ｍ／ｈ。
    （３）前記溶解槽の幅方向における側部付近における、前記下流側表層流の平均流速をＶ２Ｓとするとき、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．５。     A molten glass production method for producing molten glass using a molten glass production apparatus having a melting tank for melting glass raw materials,
    The dissolution tank has a burner for heating the upper space of the dissolution tank,
    In the vicinity of the bottom of the melting tank, there are a plurality of bubblers over the width direction of the molten glass flow path,
    When the length of molten glass flow path of the melting tank and L F, the distance from the upstream end of the molten glass flow path to the columns of said plurality of bubblers is 0.4 L F ~ 0.55 L F the dissolution A method for producing a molten glass, characterized in that the molten glass is produced under a condition that the flow of the molten glass in the tank satisfies the following (1) to (3).
    (1) Out of the upstream circulating flow of molten glass formed upstream of the plurality of bubblers, the flow near the surface of the molten glass that moves in the upstream direction of the melting tank is used as the upstream surface layer of the molten glass. When the average flow velocity of the upstream surface layer flow near the center in the width direction of the dissolution tank is V 1C , V 1C is more than 0 m / h and not more than 20 m / h.
    (2) Out of the downstream circulation flow of the molten glass formed downstream of the plurality of bubblers, the flow near the surface of the molten glass that moves in the downstream direction of the melting tank is used as the downstream surface layer of the molten glass. and flow, in the vicinity of the center in the width direction of the melting tank, when the average flow velocity of the downstream side surface current and V 2C, V 2C = 0.1 ~ 30m / h.
    (3) When the average flow velocity of the downstream surface layer flow in the vicinity of the side portion in the width direction of the dissolution tank is V 2S , | (V 2C −V 2S ) / V 2C | = 0 to 0.5.
  2. 　前記複数のバブラーが、前記溶解槽の溶融ガラス流路方向における位置が互いに異なる、複数の第１のバブラーと、複数の第２のバブラーと、で構成され、前記第２のバブラーは、前記第１のバブラーよりも溶融ガラス流路の下流側に位置し、
    　前記溶融ガラス流路の上流端から前記第１のバブラーの列までの距離が０．４ＬＦ～０．５ＬＦであり、前記溶融ガラス流路の下流端から前記第２のバブラーの列までの距離が０．４５ＬＦ～０．５５ＬＦであり、前記第１のバブラーの列と、前記第２のバブラーの列との距離ＬPが５００～１０００ｍｍであり、
    　前記溶解槽での溶融ガラスの流路方向における、前記第１のバブラーの列と該列の上流側に直近のバーナーとの距離ＬＢ１が０～２０００ｍｍであり、
    　前記溶解槽での溶融ガラスの流路方向における、前記第２のバブラーの列と該列の下流側に直近のバーナーとの距離ＬＢ２が８００～２５００ｍｍであり、
    　かつ、ＬＢ２＞ＬＢ１であり、
    　前記溶解槽での溶融ガラスの流れが、下記（１）～（３）を満たす条件で溶融ガラスを製造することを特徴とする請求項１に記載の溶融ガラス製造方法。
    （１）前記第１のバブラーよりも上流側に形成される溶融ガラスの上流側循環流のうち、前記溶解槽の上流方向に移動する、溶融ガラスの表面付近の流れを、溶融ガラスの上流側表層流とし、前記溶解槽の幅方向における中央付近における、該上流側表層流の平均流速をＶ１Ｃとするとき、Ｖ１Ｃが０ｍ／ｈ超２０ｍ／ｈ以下。
    （２）前記第２のバブラーよりも下流側に形成される溶融ガラスの下流側循環流のうち、前記溶解槽の下流方向に移動する、溶融ガラスの表面付近の流れを、溶融ガラスの下流側表層流とし、前記溶解槽の幅方向における中央付近における、該下流側表層流の平均流速をＶ２Ｃとするとき、Ｖ２Ｃ＝０．１～３０ｍ／ｈ。
    （３）前記溶解槽の幅方向における側部付近における、前記下流側表層流の平均流速をＶ２Ｓとするとき、│（Ｖ２Ｃ－Ｖ２Ｓ）／Ｖ２Ｃ│＝０～０．５。     The plurality of bubblers are composed of a plurality of first bubblers and a plurality of second bubblers whose positions in the molten glass flow path direction of the melting tank are different from each other, and the second bubbler includes the first bubbler, Located on the downstream side of the molten glass flow path from 1 bubbler,
    The distance from the upstream end of the molten glass flow path to the first row of bubblers is 0.4 L F to 0.5 L F , and the distance from the downstream end of the molten glass flow path to the second bubbler row The distance is 0.45L F to 0.55L F , and the distance L P between the first bubbler row and the second bubbler row is 500 to 1000 mm,
    A distance L B1 between the row of the first bubblers and the burner closest to the upstream side of the row in the flow direction of the molten glass in the melting tank is 0 to 2000 mm;
    The distance L B2 between the second bubbler row and the burner nearest to the downstream side of the row in the flow direction of the molten glass in the melting tank is 800 to 2500 mm,
    And L B2 > L B1 ,
    The method for producing molten glass according to claim 1, wherein the molten glass is produced under a condition that the flow of the molten glass in the melting tank satisfies the following (1) to (3).
    (1) Of the upstream circulating flow of the molten glass formed upstream of the first bubbler, the flow near the surface of the molten glass that moves in the upstream direction of the melting tank is the upstream side of the molten glass. When the average flow velocity of the upstream surface layer flow in the vicinity of the center in the width direction of the dissolution tank is V 1C , V 1C is more than 0 m / h and not more than 20 m / h.
    (2) Of the downstream circulating flow of the molten glass formed downstream of the second bubbler, the flow near the surface of the molten glass that moves in the downstream direction of the melting tank is the downstream side of the molten glass. V 2C = 0.1 to 30 m / h when the average flow velocity of the downstream surface layer flow near the center in the width direction of the dissolution tank is V 2C .
    (3) When the average flow velocity of the downstream surface layer flow in the vicinity of the side portion in the width direction of the dissolution tank is V 2S , | (V 2C −V 2S ) / V 2C | = 0 to 0.5.
  3. 　前記Ｖ１Ｃは、前記溶融ガラス流路の上流端＋５００ｍｍ～０．３５ＬＦの位置で測定され、
    　前記Ｖ２ＣおよびＶ２Ｓは、前記溶融ガラス流路の上流端から０．６ＬＦ～ＬＦ－５００ｍｍの位置で測定される、請求項１または２に記載の溶融ガラス製造方法。     The V 1C is measured at the upstream end of the molten glass flow path +500 mm to 0.35 L F ,
    The method for producing molten glass according to claim 1 or 2, wherein the V 2C and V 2S are measured at a position of 0.6 L F to L F -500 mm from an upstream end of the molten glass flow path.
  4. 　前記溶解槽の溶融ガラス流路の幅をＷ（ｍｍ）とするとき、前記溶解槽の幅方向において、前記Ｖ１Ｃおよび前記Ｖ２Ｃが２／５Ｗ～３／５Ｗの位置で測定され、前記Ｖ２Ｓが０～１／４Ｗの位置で測定される、請求項１～３のいずれか一項に記載の溶融ガラス製造方法。 When the width of the molten glass flow path of the melting tank is W (mm), the V 1C and the V 2C are measured at a position of 2/5 W to 3/5 W in the width direction of the melting tank, and the V The method for producing molten glass according to any one of claims 1 to 3, wherein 2S is measured at a position of 0 to 1/4 W.
  5. 　請求項１～４のいずれか一項に記載の溶融ガラス製造方法により得られた溶融ガラスを板ガラスに成形する板ガラス製造方法。 A plate glass manufacturing method in which molten glass obtained by the molten glass manufacturing method according to any one of claims 1 to 4 is formed into a plate glass.
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