WO2013145922A1 - Method for producing glass plate - Google Patents

Method for producing glass plate Download PDF

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Publication number
WO2013145922A1
WO2013145922A1 PCT/JP2013/053756 JP2013053756W WO2013145922A1 WO 2013145922 A1 WO2013145922 A1 WO 2013145922A1 JP 2013053756 W JP2013053756 W JP 2013053756W WO 2013145922 A1 WO2013145922 A1 WO 2013145922A1
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WIPO (PCT)
Prior art keywords
glass
molten
brick
oxide
glass plate
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PCT/JP2013/053756
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French (fr)
Japanese (ja)
Inventor
丈宜 三浦
史朗 谷井
泰夫 林
Original Assignee
旭硝子株式会社
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Priority to CN201380000355.4A priority Critical patent/CN103492329B/en
Priority to KR1020137012611A priority patent/KR101384375B1/en
Publication of WO2013145922A1 publication Critical patent/WO2013145922A1/en

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    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B18/00Shaping glass in contact with the surface of a liquid
    • C03B18/02Forming sheets
    • C03B18/16Construction of the float tank; Use of material for the float tank; Coating or protection of the tank wall
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B18/00Shaping glass in contact with the surface of a liquid
    • C03B18/02Forming sheets
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL 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
    • C03C3/00Glass compositions
    • C03C3/04Glass compositions containing silica
    • C03C3/076Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/089Glass compositions containing silica with 40% to 90% silica, by weight containing boron
    • C03C3/091Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
    • C03C3/093Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium containing zinc or zirconium
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C04B35/101Refractories from grain sized mixtures
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C04B35/101Refractories from grain sized mixtures
    • C04B35/106Refractories from grain sized mixtures containing zirconium oxide or zircon (ZrSiO4)
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3201Alkali metal oxides or oxide-forming salts thereof
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3205Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
    • C04B2235/3206Magnesium oxides or oxide-forming salts thereof
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3205Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
    • C04B2235/3208Calcium oxide or oxide-forming salts thereof, e.g. lime
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00Technologies relating to the processing of minerals
    • Y02P40/50Glass production, e.g. reusing waste heat during processing or shaping
    • Y02P40/57Improving the yield, e-g- reduction of reject rates

Definitions

  • the present invention relates to a method for producing a glass plate.
  • the float method is widely used as a glass plate forming method.
  • molten glass continuously supplied onto molten tin in a bathtub is caused to flow on molten tin to be formed into a strip shape (for example, see Patent Document 1).
  • the atmosphere on the molten tin is a reducing atmosphere containing hydrogen gas in order to prevent oxidation of the molten tin.
  • the bathtub is composed of, for example, a box-shaped metal case opened upward, and a bottom brick and a side brick installed in the metal case.
  • alumina (Al 2 O 3 ) -silica (SiO 2 ) brick is generally used as the bottom brick and the side brick.
  • the molten tin in the bathtub is heated from above, the temperature becomes lower as it goes downward. Therefore, gas components (for example, oxygen, hydrogen, water, etc.) dissolved in the molten tin are supersaturated on the upper surface of the relatively low temperature bottom brick to form bubbles. Moreover, the gas which permeate
  • gas components for example, oxygen, hydrogen, water, etc.
  • the yield of glass plates was low because the locations where FOBBs occurred were dispersed.
  • the present inventors have found that the glass of the glass plate is conspicuous in the case of alkali-free glass having a high molding temperature as compared with general soda lime glass.
  • This invention was made in view of the said subject, Comprising: It aims at provision of the manufacturing method of the glass plate of an alkali free glass with a favorable yield.
  • a method for producing a glass plate includes: In the method for producing a glass plate, the method includes a step of forming molten glass that is continuously supplied onto molten tin in a bath and flowing on the molten tin.
  • the glass of the glass plate is alkali-free glass, and the temperature of the molten glass at which the viscosity of the molten glass is 10 4 dPa ⁇ s is 1200 ° C.
  • Each bottom brick of the bathtub has a total content of low melting point elements of 20% by mass or less in terms of oxide,
  • the low melting point element is an element having a lower eutectic point in the binary system of the oxide of the low melting point element and tin oxide (SnO) than the maximum temperature of the upper surface of the corresponding bottom brick.
  • FIG. 3 is a SEM photograph of a cut surface of a crucible according to Comparative Example 1. It is the SEM photograph which expanded a part of FIG. It is the map of Sn element which carried out the element analysis of the same area
  • the glass plate manufacturing method according to the present embodiment includes, for example, a melting step, a forming step, a slow cooling step, and a cutting step.
  • glass raw materials prepared by mixing a plurality of types of raw materials are melted to obtain molten glass.
  • the glass raw material is put into the melting furnace, it is melted by the radiant heat of the flame injected from the burner to become molten glass.
  • the molten glass obtained in the melting step is continuously supplied onto the molten tin in the bathtub, and the molten glass is flowed on the molten tin to be molded to obtain a plate-like glass (so-called glass ribbon).
  • the plate glass is cooled while flowing in a predetermined direction, and pulled up from the molten tin.
  • the glass sheet obtained in the molding step is slowly cooled in a slow cooling furnace.
  • the plate glass is gradually cooled while being transported horizontally on the roll from the inlet to the outlet of the slow cooling furnace in the slow cooling furnace.
  • the sheet glass slowly cooled in the slow cooling step is cut into a predetermined size by a cutting machine.
  • both edges (so-called ears) in the width direction of the sheet glass are cut off. This is because both edges in the width direction of the plate-like glass become thick due to the influence of surface tension and the like.
  • the glass of the glass plate is an alkali-free glass that does not substantially contain an alkali metal oxide (Na 2 O, K 2 O, Li 2 O, etc.).
  • the alkali-free glass may have a total content of alkali metal oxides of 0.1% by mass or less, and is used, for example, as a substrate for a liquid crystal display.
  • the alkali-free glass is, for example, SiO 2 : 50% to 73% (preferably 50 to 66%), Al 2 O 3 : 10.5% to 24%, B 2 O 3 in terms of mass% based on oxide. : 0% to 12%, MgO: 0% to 8%, CaO: 0% to 14.5%, SrO: 0% to 24%, BaO: 0% to 13.5%, ZrO 2 : 0% to 5% MgO + CaO + SrO + BaO: 8% to 29.5% (preferably 9% to 29.5%).
  • SiO 2 58% to 66%
  • Al 2 O 3 15% to 22%, expressed by mass% based on oxide.
  • B 2 O 3 5% ⁇ 12%
  • CaO 0% ⁇ 9%
  • SrO 3% ⁇ 12.5%
  • BaO 0% ⁇ containing 2%
  • MgO + CaO + SrO + BaO 9% to 18%.
  • the alkali-free glass is preferably expressed in terms of mass% 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% to 8%, CaO: 0% to 9%, SrO: 0% to 16%, BaO: 0% to 2.5%, MgO + CaO + SrO + BaO: 8 % To 26%.
  • the temperature of the molten glass at which the viscosity of the molten glass is 10 4 dPa ⁇ s (poise) is 1200 ° C. or higher.
  • the place where the viscosity of the molten glass is about 10 4 dPa ⁇ s is usually set near the inlet 12 of the float bath 10 (see FIG. 1) used in the molding process.
  • the molten glass supplied onto the molten tin M at the inlet 12 of the float bath 10 is molded while flowing in a predetermined direction.
  • FIG. 1 is an explanatory diagram of a float bath used in a glass plate forming process according to an embodiment of the present invention.
  • Float bath 10 (hereinafter simply referred to as “bath 10”) is formed by causing molten glass G continuously supplied onto molten tin M in bathtub 22 to flow on molten tin M.
  • the molten glass G is supplied onto the molten tin M near the inlet 12 of the bath 10, cooled while flowing in a predetermined direction, and pulled up from the molten tin M near the outlet 14 of the bath 10.
  • the bath 10 includes a bathtub 22 that accommodates molten tin M, a side wall 24 that is installed along the outer peripheral upper edge of the bathtub 22, a ceiling 26 that is connected to the side wall 24 and covers the top of the bathtub 22.
  • the ceiling 26 is provided with a gas supply path 30 for supplying a reducing gas to a space 28 formed between the bathtub 22 and the ceiling 26.
  • a heater 32 as a heating source is inserted into the gas supply path 30.
  • the gas supply path 30 supplies a reducing gas to the space 28 in the bus 10 in order to prevent the molten tin M from being oxidized.
  • the reducing gas contains, for example, 1 to 15% by volume of hydrogen gas and 85 to 99% by volume of nitrogen gas.
  • the space 28 in the bus 10 is set to a pressure higher than the atmospheric pressure in order to prevent air from being mixed in through a gap between bricks constituting the side wall 24.
  • a plurality of heaters 32 are provided, for example, at intervals in the flow direction (X direction) and the width direction (Y direction) of the molten glass G.
  • the output of the heater 32 is controlled so that the temperature of the molten glass G decreases as it goes from the inlet 12 to the outlet 14 of the bus 10.
  • the output of the heater 32 is controlled so that the thickness of the molten glass G is uniform in the width direction (Y direction).
  • the bathtub 22 includes a box-shaped metal case 34 opened upward, and a bottom brick 36 and a side brick 38 installed in the metal case 34.
  • the metal case 34 prevents air from entering the bathtub 22 from the side or from below.
  • the plurality of bottom bricks 36 are two-dimensionally arranged at a slight interval so as not to contact each other due to thermal expansion.
  • the plurality of bottom bricks 36 are surrounded by a plurality of side bricks 38 arranged in a ring shape.
  • the molten tin M in the bathtub 22 is heated from above by the heater 32, the temperature becomes lower as it goes downward. Therefore, gas components (for example, oxygen, hydrogen, water, etc.) dissolved in the molten tin M are supersaturated on the upper surface 36a of the relatively low temperature bottom brick 36 to form bubbles B. Further, gas (for example, hydrogen) that has permeated through the bottom brick 36 forms bubbles B on the upper surface 36 a of the bottom brick 36.
  • gas components for example, oxygen, hydrogen, water, etc.
  • the inventors of the present invention focused on the fact that the number of bubbles B decreases as the size of each bubble B increases, when the total mass of bubbles B generated per unit time is the same. In order for the bubbles B to grow greatly on the bottom brick 36, it is important to reduce the wettability of the molten tin M with respect to the bottom brick 36.
  • FIG. 2 is a diagram showing the relationship between the wettability of molten tin with respect to the bottom brick and the shape of the bubbles formed on the bottom brick according to an embodiment of the present invention.
  • FIG. 3 is a diagram showing the relationship between the wettability of molten tin with respect to a conventional bottom brick and the shape of bubbles formed on the bottom brick.
  • the wettability of molten tin with respect to the bottom brick of the present embodiment of FIG. 2 is lower than the wettability of molten tin with respect to the conventional bottom brick of FIG.
  • Low wettability means that molten tin is difficult to wet with respect to the bottom brick
  • high wettability means that molten tin is easily wetted with respect to the bottom brick.
  • the wettability of the molten metal to the oxide is low, the wettability of the molten tin M to the bottom brick 6 is low at the start of production of the glass plate.
  • tin oxide slightly contained as an impurity in the molten tin M reacts with the bottom brick 6, and a reaction layer (modified layer) is formed on the surface of the bottom brick 6. Will be higher.
  • each bottom brick 36 is a brick whose total content of low melting point elements is 20% by mass or less in terms of oxide.
  • the “low melting point element” is an element whose eutectic point in the binary system of the low melting point element oxide and tin oxide (SnO) is lower than the maximum temperature of the upper surface 36a of the corresponding bottom brick 36. is there. When the temperature becomes higher than the eutectic point, a liquid phase is formed, and the reaction between the oxide of the low melting point element and tin oxide proceeds rapidly.
  • Tin oxide is contained in the molten tin M in a small amount as an impurity, and the tin oxide in the molten tin M selectively reacts with the portion of the bottom brick 36 where the concentration of the low melting point element is high.
  • the tin oxide contained in the molten tin M is air that has entered the bus 10 when the side wall 24 is opened to the atmosphere for production reasons, or air that has entered the bus 10 from the gaps between the bricks constituting the side wall 24. It is formed by exposing molten tin M.
  • “the total content of low melting point elements” is the content of one low melting point element when the number of low melting point elements is one, and when there are a plurality of low melting point elements, The total content of elements.
  • the kind of the low melting point element may be different for each bottom brick 36.
  • the low melting point element may not be present in the bottom brick 36.
  • low melting point element examples include silicon (Si).
  • the eutectic point of silicon oxide (SiO 2 ) and tin oxide is about 850 ° C., which is lower than the maximum temperature of the upper surface 36 a of most bottom bricks 36.
  • the total content of the low melting point elements is 20% by mass or less (preferably 15% by mass or less, more preferably 10% by mass or less) in terms of oxide.
  • the brick 36 and the molten tin M hardly react. If the total content of the low melting point elements is 20% by mass or less in terms of oxide, most of the low melting point elements constitute oxides with other elements in the bottom brick 36, and the melting point of the oxides. This is because the temperature is higher than the maximum temperature of the upper surface 36 a of the bottom brick 36. Since each bottom brick 36 and molten tin M hardly react, the wettability of molten tin M with respect to each bottom brick 36 is low even when time elapses from the start of glass plate production.
  • the total content of low melting point elements in each bottom brick 36 is 20% by mass or less in terms of oxides, but the total content of low melting point elements in all bottom bricks 36 is in terms of oxides. It may not be 20 mass% or less.
  • the maximum temperature of the upper surface of the bottom brick is equal to or lower than the temperature of the molten glass G at which the viscosity of the molten glass G is 10 4 dPa ⁇ s, and the eutectic point in the binary system of the low melting point element oxide and tin oxide
  • the total content of the low melting point elements may be 20% by mass or less in terms of oxide, and may exceed 0% by mass, at least one bottom brick having a temperature exceeding.
  • the size of each bubble B increases, if the total mass of bubbles B generated per unit time is the same, the number of bubbles B generated per unit time decreases.
  • the number of FOBBs formed on the bottom surface of the glass plate is reduced, and the yield of FOBB is increased.
  • the alkali-free glass has a higher molding temperature of the molten glass G and a higher temperature of the upper surface 36a of the bottom brick 36 than a general soda lime glass. Therefore, when the chemical composition of the bottom brick 36 is the same, the reaction between the bottom brick 36 and the molten tin M is likely to proceed.
  • alkali-free glass does not substantially contain alkali metal elements (for example, Na, K), so that the bottom brick 36 is hardly converted to nepheline ((Na, K) AlSiO 4 ).
  • alkali metal elements for example, Na, K
  • nepheline (Na, K) AlSiO 4
  • Nephelinization forms a dense glass layer on the bottom brick 36 and suppresses gas permeation from the inside of the bottom brick 36 to the upper surface 36a.
  • nephelinization hardly occurs, so that the total mass of bubbles B generated per unit time increases.
  • the bottom bricks 36 and the molten tin M hardly react with each other, so that the alteration of the upper surface 36a of the bottom brick 36 is suppressed, and the detachment of the altered particles is suppressed. Since the desorbed particles float up to the interface between the molten tin M and the molten glass G and become a defect of the molten glass G, the quality of the glass plate can be improved by suppressing the desorption of the particles.
  • a viscous fired brick such as alumina (Al 2 O 3 ) -calcia (CaO) brick or alumina (Al 2 O 3 ) -zirconia (ZrO 2 ) brick is used.
  • SiO 2 or the like is used as a sintering aid, and there is a portion having a high SiO 2 concentration.
  • the alumina-calcia brick contains, for example, Al 2 O 3 : 40% to 85%, CaO: 10% to 40%, and SiO 2 : 0.5% to 20% in terms of mass% based on oxide.
  • the SiO 2 content is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 7% by mass or less, particularly preferably 3% by mass or less, and even more preferably 1% by mass or less.
  • Alumina-zirconia bricks contain, for example, Al 2 O 3 : 40% to 55%, ZrO 2 : 30% to 45%, SiO 2 : 0.5% to 20% in terms of mass% based on oxide. .
  • the SiO 2 content is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 7% by mass or less, particularly preferably 3% by mass or less, and even more preferably 1% by mass or less.
  • the side brick 38 may have a total content of low melting point elements of 20% by mass or less in terms of oxide, or may exceed 20% by mass, as with the bottom brick 36. Since the molten glass G is inside the side brick 38 at the time of molding, the bubbles formed on the inner wall surface of the side brick 38 do not cause FOBB.
  • the glass plate of the said embodiment is used as a board
  • a use may be various.
  • the glass plate may be used as a substrate for an organic EL display or a cover glass for a touch panel.
  • Example 1 First, a brick is processed to prepare a crucible, and metal tin is put into the prepared crucible, installed in an electric furnace, the atmosphere in the electric furnace is replaced, and then the metal tin is melted at 1000 ° C. for 60 minutes. The reactivity between molten tin and crucible was investigated.
  • brick A which is an alumina (Al 2 O 3 ) -calcia (CaO) brick
  • Brick A is expressed in terms of mass% on an oxide basis, SiO 2 : 5.7%, Al 2 O 3 : 66.0%, CaO: 26.0%, MgO: 1.5%, Na 2 O: 0. .3%, Fe 2 O 3 : 0.1%, and other components are each less than 0.1%.
  • the chemical composition of the brick A was measured with a fluorescent X-ray analyzer (manufactured by Rigaku Denki Kogyo Co., Ltd., ZSX100e).
  • the crucible was processed into a bottomed cylindrical shape (inner diameter 6 mm, inner dimension height 6 mm, bottom wall thickness 3 mm, side wall thickness 2 mm).
  • Metal tin with a purity of 99.95% by mass (manufactured by Kanto Chemical Co., Ltd., special grade) was used. Metal tin was weighed so that the thickness of molten tin was 5 mm and placed in a crucible.
  • the atmosphere in the electric furnace was replaced by evacuating the electric furnace to 1 kPa with a vacuum pump and then supplying gas into the electric furnace through a gas supply pipe.
  • gas nitrogen gas with an oxygen concentration of 1000 ppm by volume was used. Nitrogen gas was used because nitrogen gas has low reactivity with oxygen gas and does not affect the oxygen concentration.
  • the reactivity between the molten tin and the crucible was examined by solidifying the crucible cooled to room temperature with a resin and then cutting it, and observing the cut surface with an SEM (Scanning Electron Microscope, manufactured by Keyence Corporation, VE-9800).
  • FIG. 4 shows an SEM photograph of the cut surface of the crucible according to Example 1. As apparent from FIG. 4, no reaction layer with molten tin 44 was observed on the inner bottom surface of the crucible 41. Further, a gap 45 is partially formed between the crucible 41 and the molten tin 44, and it can be seen that the wettability of the molten tin 44 with respect to the crucible 41 is low.
  • FIG. 5 shows a test for examining the number of defects formed in the glass for evaluation in Example 1.
  • a crucible 51 in which brick A was processed was prepared, metal tin was put into the prepared crucible 51, and an evaluation glass 53 was placed on a carbon jig 52.
  • the crucible 51 is installed in the electric furnace of the glove box, the atmosphere in the electric furnace is replaced, the temperature in the electric furnace is increased, and the evaluation glass 53 is thermally deformed by its own weight to be formed on the molten tin 54. I put it.
  • the temperature in the electric furnace at 1100 ° C.
  • the temperature in the electric furnace was lowered to 800 ° C., and the solidified evaluation glass 53 was manually pulled up from the molten tin 54. Subsequently, the glass for evaluation 53 was gradually cooled in an electric furnace, and the number of FOBBs formed in the portion of the glass for evaluation 53 in contact with the molten tin 54 was examined.
  • the crucible 51 was processed into a bottomed cylindrical shape (inner diameter 60 mm, inner dimension height 40 mm, bottom wall thickness 10 mm, side wall thickness 10 mm).
  • Metal tin with a purity of 99.95% by mass (manufactured by Kanto Chemical Co., Ltd., special grade) was used. Metal tin was weighed so that the thickness of molten tin was 20 mm and placed in a crucible.
  • the alkali free glass plate (length 40mm, width 40mm, thickness 0.7mm) was prepared.
  • This non-alkali glass plate is expressed in terms of mass% based on oxide, SiO 2 : 60.0%, Al 2 O 3 : 17.0%, B 2 O 3 : 8.0%, MgO: 3.0% CaO: 4.5% and SrO: 7.5%.
  • the chemical composition of the glass plate was measured with a fluorescent X-ray analyzer (manufactured by Rigaku Denki Kogyo Co., Ltd., ZSX100e).
  • the atmosphere in the electric furnace was replaced by evacuating the electric furnace to 1 kPa with a vacuum pump and then supplying gas into the electric furnace through a gas supply pipe.
  • gas nitrogen gas having a hydrogen concentration of 10% by volume was used.
  • the number of defects (FOBB) formed in the glass for evaluation 53 was measured by cooling the glass for evaluation 53 to room temperature, and then observing the portion (5 mm ⁇ 5 mm) in contact with the molten tin 54 of the glass for evaluation 53 with an optical microscope. I investigated. The number of large defects (diameter over 300 ⁇ m) was 0, and the number of small defects (diameter 10 to 300 ⁇ m) was 2. The total number of small defects and large defects was 10% or less as compared with the case of Comparative Example 1 described later.
  • the reason for the small number of defects is that the brick A, which is the material of the crucible 51, has a low content of Si, which is a low melting point element. Since the Si content is small, the crucible 41 and the molten tin 44 hardly react as shown in FIG. 4, and the wettability of the molten tin 44 with respect to the crucible 41 is low. Since the wettability is low, as shown in FIG. 3, the bubbles formed on the inner bottom surface of the crucible do not easily float and grow large while retaining the bubbles, and as a result, the number of small defects is small.
  • Example 2 In Example 2, brick B, which is an alumina (Al 2 O 3 ) -calcia (CaO) brick, was prepared, and the number of defects formed in the evaluation glass was examined in the same manner as in Example 1. Brick B is expressed in terms of mass% based on oxide, SiO 2 : 5.8%, Al 2 O 3 : 82.4%, CaO: 10.2%, MgO: 1.2%, Na 2 O: 0 0.2%, Fe 2 O 3 : 0.2%, and other components are each less than 0.1%.
  • Brick B is expressed in terms of mass% based on oxide, SiO 2 : 5.8%, Al 2 O 3 : 82.4%, CaO: 10.2%, MgO: 1.2%, Na 2 O: 0 0.2%, Fe 2 O 3 : 0.2%, and other components are each less than 0.1%.
  • the number of large defects is 0, and the number of small defects (diameter 10 to 300 ⁇ m) is 10 or less.
  • Example 3 In Example 3, the number of defects formed in the glass for evaluation was examined in the same manner as in Example 1 except that brick C, which is an alumina (Al 2 O 3 ) -zirconia (ZrO 2 ) -based brick, was prepared. It was. Brick C contains SiO 2 : 13.5%, ZrO 2 : 33.0%, Al 2 O 3 : 52.0%, Na 2 O: 1.3% in terms of mass% based on oxide. The other components are each less than 0.1%.
  • brick C which is an alumina (Al 2 O 3 ) -zirconia (ZrO 2 ) -based brick, was prepared. It was. Brick C contains SiO 2 : 13.5%, ZrO 2 : 33.0%, Al 2 O 3 : 52.0%, Na 2 O: 1.3% in terms of mass% based on oxide. The other components are each less than 0.1%.
  • the number of large defects is 0, and the number of small defects (diameter 10 to 300 ⁇ m) is 15.
  • Comparative Example 1 In Comparative Example 1, the reactivity between brick and molten tin was examined in the same manner as in Example 1 except that brick D, which is an alumina (Al 2 O 3 ) -silica (SiO 2 ) brick, was prepared.
  • Brick D is expressed in terms of mass% based on oxide, SiO 2 : 58.0%, Al 2 O 3 : 37.0%, CaO: 0.4%, MgO: 0.1%, P 2 O 5 : Contains 0.4%, Na 2 O: 0.1%, K 2 O: 0.9%, Fe 2 O 3 : 1.2%, TiO 2 : 0.9%, ZrO 2 : 0.1%
  • the other components are each less than 0.1%.
  • FIG. 6 shows a SEM photograph of the cut surface of the crucible according to Comparative Example 1.
  • FIG. 7 shows an SEM photograph in which a part of FIG. 6 is enlarged.
  • a reaction layer 66 with molten tin 64 was found on the inner bottom of the crucible 61. Further, it is understood that the crucible 61 and the molten tin 64 are in close contact with each other, and the wettability of the molten tin 64 with respect to the crucible 61 is high.
  • FIG. 8 is a map of Sn element obtained by elemental analysis of the same region as the SEM photograph of FIG. 7 by EDS
  • FIG. 9 is a map of Al element obtained by elemental analysis of the same region as the SEM photograph of FIG. 7 by EDS
  • EDS Energy Dispersive X-ray Spectrometry
  • Comparative Example 1 the number of defects formed in the glass for evaluation was examined in the same manner as in Example 1 except that the brick D was used as a brick. As a result, the number of large defects (diameter exceeding 300 ⁇ m) was 0, and the number of small defects (diameter 10 to 300 ⁇ m) was 60.
  • the brick D which is a material for the crucible, has a high content of Si, which is a low melting point element. Since the Si content is large, a reaction layer 66 with molten tin 64 is formed on the crucible 61 as shown in FIGS. 6 and 7, and the wettability of the molten tin 64 with respect to the crucible 61 is high. Since the wettability is high, the bubbles formed on the inner bottom surface of the crucible float in a small state as shown in FIG. 2, and as a result, the number of small defects is large.
  • brick E which is an alumina (Al 2 O 3 ) -silica (SiO 2 ) brick, was prepared, and the number of defects formed in the evaluation glass was examined in the same manner as in Comparative Example 1.
  • Brick E is expressed in terms of mass% based on oxide, SiO 2 : 58.0%, Al 2 O 3 : 37.0%, CaO: 0.2%, MgO: 0.3%, Na 2 O: 0 0.8%, K 2 O: 0.9%, Fe 2 O 3 : 1.1%, TiO 2 : 1.6%, and other components are each less than 0.1%.
  • the number of large defects (diameter exceeding 300 ⁇ m) was 0, and the number of small defects (diameter 10 to 300 ⁇ m) was 70.
  • Reference Example 1 was the same as Comparative Example 1 except that a reducing gas composed of 10% by volume hydrogen gas and 90% by volume nitrogen gas was used as the gas supplied into the electric furnace after evacuation. The reactivity between brick D and molten tin was investigated.
  • FIG. 11 shows an SEM photograph of the cut surface of the crucible according to Reference Example 1. As is clear from FIG. 11, no reaction layer with molten tin 74 was observed in the crucible 71. Further, a gap 75 is partially formed between the crucible 71 and the molten tin 74, and it can be seen that the wettability of the molten tin 74 with respect to the crucible 71 is low.
  • Example 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.
  • Table 1 the composition of bricks is shown only for SiO 2 , Al 2 O 3 , CaO, MgO, and ZrO 2 .

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Abstract

Provided is a method for producing a glass plate comprising a step of making molten glass (G) flow on molten tin (M) and molding the same, the molten glass (G) being continuously supplied onto the molten tin (M) in a bath (22), wherein the glass for the glass plate is an alkali free glass and the temperature of the molten glass (G) at which viscosity of the molten glass (G) becomes 104dPa·s is 1,200°C or more. Each bottom brick (36) of the bath (22) has a total amount of a low melting element of 20 mass% or less in terms of oxides. The low melting element is an element in which the eutectic point in a binary system of oxide of the low melting element and tin oxide (SnO) is lower than the maximum temperature of an upper face (36a) of the corresponding bottom brick (36).

Description

ガラス板の製造方法Manufacturing method of glass plate
 本発明は、ガラス板の製造方法に関する。 The present invention relates to a method for producing a glass plate.
 ガラス板の成形方法として、フロート法が広く用いられている。フロート法は、浴槽内の溶融スズ上に連続的に供給される溶融ガラスを溶融スズ上で流動させて帯板状に成形する(例えば、特許文献1参照)。 The float method is widely used as a glass plate forming method. In the float process, molten glass continuously supplied onto molten tin in a bathtub is caused to flow on molten tin to be formed into a strip shape (for example, see Patent Document 1).
 溶融スズ上の雰囲気は、溶融スズの酸化を防止するため、水素ガスを含む還元雰囲気とされる。 The atmosphere on the molten tin is a reducing atmosphere containing hydrogen gas in order to prevent oxidation of the molten tin.
 浴槽は、例えば、上方に開放された箱状の金属ケース、並びに金属ケース内に設置されるボトム煉瓦及びサイド煉瓦で構成される。ボトム煉瓦及びサイド煉瓦としては、一般的にアルミナ(Al)-シリカ(SiO)系煉瓦が使用されている。 The bathtub is composed of, for example, a box-shaped metal case opened upward, and a bottom brick and a side brick installed in the metal case. As the bottom brick and the side brick, alumina (Al 2 O 3 ) -silica (SiO 2 ) brick is generally used.
日本国特開昭50-3414号公報Japanese Unexamined Patent Publication No. 50-3414
 浴槽内の溶融スズは、上方から加熱されるので、下方に向かうほど低温になる。そのため、溶融スズに溶存したガス成分(例えば酸素や水素、水など)は、比較的低温のボトム煉瓦の上面で過飽和析出し、気泡を形成する。また、ボトム煉瓦中を透過したガスが、ボトム煉瓦の上面で気泡を形成する。 Since the molten tin in the bathtub is heated from above, the temperature becomes lower as it goes downward. Therefore, gas components (for example, oxygen, hydrogen, water, etc.) dissolved in the molten tin are supersaturated on the upper surface of the relatively low temperature bottom brick to form bubbles. Moreover, the gas which permeate | transmitted the bottom brick forms a bubble in the upper surface of a bottom brick.
 これらの気泡は、ある程度の大きさに成長すると、ボトム煉瓦の上面から離れ、溶融スズと溶融ガラスの界面まで浮上し、溶融ガラスの下面に凹状の欠陥を形成する。その結果、製品であるガラス板の溶融スズとの接触面(ボトム面)に凹状の欠陥(FOBB(Fine Open Bottom Bubble))が形成される。 When these bubbles grow to a certain size, they move away from the top surface of the bottom brick, rise to the interface between the molten tin and the molten glass, and form a concave defect on the bottom surface of the molten glass. As a result, a concave defect (FOBB (Fine Open Bottom Bubble)) is formed on the contact surface (bottom surface) of the glass plate that is the product with the molten tin.
 従来、FOBBの発生する場所が分散していたため、ガラス板の歩留まりが低かった。特に、ガラス板のガラスが、一般的なソーダライムガラスに比べて、高い成形温度の無アルカリガラスの場合に顕著であることを今回本発明者らは発見した。 Conventionally, the yield of glass plates was low because the locations where FOBBs occurred were dispersed. In particular, the present inventors have found that the glass of the glass plate is conspicuous in the case of alkali-free glass having a high molding temperature as compared with general soda lime glass.
 本発明は、上記課題に鑑みてなされたものであって、歩留まりの良好な無アルカリガラスのガラス板の製造方法の提供を目的とする。 This invention was made in view of the said subject, Comprising: It aims at provision of the manufacturing method of the glass plate of an alkali free glass with a favorable yield.
 上記課題を解決するため、本発明の一態様によるガラス板の製造方法は、
 浴槽内の溶融スズ上に連続的に供給される溶融ガラスを前記溶融スズ上で流動させて成形する工程を有するガラス板の製造方法において、
 前記ガラス板のガラスは無アルカリガラスであって、前記溶融ガラスの粘度が10dPa・sとなる前記溶融ガラスの温度が1200℃以上であり、
 前記浴槽の各ボトム煉瓦は、低融点元素の合計の含有量が酸化物換算で20質量%以下であって、
 前記低融点元素は、該低融点元素の酸化物と、酸化スズ(SnO)との2成分系での共融点が、対応する前記ボトム煉瓦の上面の最高温度よりも低い元素のことである。
In order to solve the above problems, a method for producing a glass plate according to an aspect of the present invention includes:
In the method for producing a glass plate, the method includes a step of forming molten glass that is continuously supplied onto molten tin in a bath and flowing on the molten tin.
The glass of the glass plate is alkali-free glass, and the temperature of the molten glass at which the viscosity of the molten glass is 10 4 dPa · s is 1200 ° C. or higher,
Each bottom brick of the bathtub has a total content of low melting point elements of 20% by mass or less in terms of oxide,
The low melting point element is an element having a lower eutectic point in the binary system of the oxide of the low melting point element and tin oxide (SnO) than the maximum temperature of the upper surface of the corresponding bottom brick.
 本発明によれば、歩留まりの良好な無アルカリガラスのガラス板の製造方法が提供される。 According to the present invention, there is provided a method for producing an alkali-free glass plate having a good yield.
本発明の一実施形態による無アルカリガラス板の成形工程で用いられるフロートバスの説明図である。It is explanatory drawing of the float bath used at the formation process of the alkali free glass plate by one Embodiment of this invention. 本発明の一実施形態によるボトム煉瓦に対する溶融スズの濡れ性と、ボトム煉瓦上で形成される気泡の形状との関係を示す図である。It is a figure which shows the relationship between the wettability of the molten tin with respect to the bottom brick by one Embodiment of this invention, and the shape of the bubble formed on a bottom brick. 従来のボトム煉瓦に対する溶融スズの濡れ性と、ボトム煉瓦上で形成される気泡の形状との関係を示す図である。It is a figure which shows the relationship between the wettability of the molten tin with respect to the conventional bottom brick, and the shape of the bubble formed on a bottom brick. 実施例1によるルツボの切断面のSEM写真である。2 is a SEM photograph of a cut surface of a crucible according to Example 1. 実施例1における評価用ガラスに形成される欠陥の数を調べる試験の説明図である。It is explanatory drawing of the test which investigates the number of the defects formed in the glass for evaluation in Example 1. FIG. 比較例1によるルツボの切断面のSEM写真である。3 is a SEM photograph of a cut surface of a crucible according to Comparative Example 1. 図6の一部を拡大したSEM写真である。It is the SEM photograph which expanded a part of FIG. 図7のSEM写真と同じ領域をEDSで元素分析したSn元素のマップである。It is the map of Sn element which carried out the element analysis of the same area | region as the SEM photograph of FIG. 7 by EDS. 図7のSEM写真と同じ領域をEDSで元素分析したAl元素のマップである。8 is a map of Al element obtained by elemental analysis of the same region as the SEM photograph of FIG. 7 by EDS. 図7のSEM写真と同じ領域をEDSで元素分析したSi元素のマップである。It is the map of Si element which carried out the element analysis of the same area | region as the SEM photograph of FIG. 7 by EDS. 参考例1によるルツボの切断面のSEM写真である。3 is a SEM photograph of a cut surface of a crucible according to Reference Example 1.
 以下、本発明を実施するための形態について図面を参照して説明する。なお、以下の図面において、同一のまたは対応する構成には、同一のまたは対応する符号を付して、説明を省略する。 Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted.
 本実施形態によるガラス板の製造方法は、例えば溶解工程、成形工程、徐冷工程、及び切断工程を有する。 The glass plate manufacturing method according to the present embodiment includes, for example, a melting step, a forming step, a slow cooling step, and a cutting step.
 溶解工程は、複数種類の原料を混ぜて調製したガラス原料を溶解して、溶融ガラスを得る。ガラス原料は、溶解炉内に投入された後、バーナから噴射される火炎の輻射熱によって溶解され、溶融ガラスとなる。 In the melting step, glass raw materials prepared by mixing a plurality of types of raw materials are melted to obtain molten glass. After the glass raw material is put into the melting furnace, it is melted by the radiant heat of the flame injected from the burner to become molten glass.
 成形工程は、溶解工程で得られる溶融ガラスを浴槽内の溶融スズ上に連続的に供給し、溶融スズ上で溶融ガラスを流動させて成形し、板状ガラス(所謂ガラスリボン)を得る。板状ガラスは、所定方向に流動しながら冷却され、溶融スズから引き上げられる。 In the forming step, the molten glass obtained in the melting step is continuously supplied onto the molten tin in the bathtub, and the molten glass is flowed on the molten tin to be molded to obtain a plate-like glass (so-called glass ribbon). The plate glass is cooled while flowing in a predetermined direction, and pulled up from the molten tin.
 徐冷工程は、成形工程で得られる板状ガラスを徐冷炉内で徐冷する。板状ガラスは、徐冷炉内において、徐冷炉の入口から出口に向けて、ロール上を水平に搬送されながら徐冷される。 In the slow cooling step, the glass sheet obtained in the molding step is slowly cooled in a slow cooling furnace. The plate glass is gradually cooled while being transported horizontally on the roll from the inlet to the outlet of the slow cooling furnace in the slow cooling furnace.
 切断工程は、徐冷工程で徐冷された板状ガラスを切断機で所定寸法に切断する。切断工程において、板状ガラスの幅方向両縁部(所謂耳部)が切除される。板状ガラスの幅方向両縁部は、表面張力等の影響で肉厚になるからである。 In the cutting step, the sheet glass slowly cooled in the slow cooling step is cut into a predetermined size by a cutting machine. In the cutting step, both edges (so-called ears) in the width direction of the sheet glass are cut off. This is because both edges in the width direction of the plate-like glass become thick due to the influence of surface tension and the like.
 このようにして、製品であるガラス板が得られる。ガラス板のガラスは、アルカリ金属酸化物(NaO、KO、LiO等)を実質的に含まない無アルカリガラスである。無アルカリガラスは、例えばアルカリ金属酸化物の含有量の合量が0.1質量%以下であってよく、例えば液晶ディスプレイ用の基板として用いられる。 In this way, a product glass plate is obtained. The glass of the glass plate is an alkali-free glass that does not substantially contain an alkali metal oxide (Na 2 O, K 2 O, Li 2 O, etc.). For example, the alkali-free glass may have a total content of alkali metal oxides of 0.1% by mass or less, and is used, for example, as a substrate for a liquid crystal display.
 無アルカリガラスは、例えば、酸化物基準の質量%表示で、SiO:50%~73%(好ましくは50~66%)、Al:10.5%~24%、B:0%~12%、MgO:0%~8%、CaO:0%~14.5%、SrO:0%~24%、BaO:0%~13.5%、ZrO:0%~5%を含有し、MgO+CaO+SrO+BaO:8%~29.5%(好ましくは9%~29.5%)である。 The alkali-free glass is, for example, SiO 2 : 50% to 73% (preferably 50 to 66%), Al 2 O 3 : 10.5% to 24%, B 2 O 3 in terms of mass% based on oxide. : 0% to 12%, MgO: 0% to 8%, CaO: 0% to 14.5%, SrO: 0% to 24%, BaO: 0% to 13.5%, ZrO 2 : 0% to 5% MgO + CaO + SrO + BaO: 8% to 29.5% (preferably 9% to 29.5%).
 無アルカリガラスは、高い歪点と高い溶解性とを両立する場合、好ましくは、酸化物基準の質量%表示で、SiO:58%~66%、Al:15%~22%、B:5%~12%、MgO:0%~8%、CaO:0%~9%、SrO:3%~12.5%、BaO:0%~2%を含有し、MgO+CaO+SrO+BaO:9%~18%である。
  無アルカリガラスは、特に高い歪点を得たい場合、好ましくは、酸化物基準の質量%表示で、SiO:54%~73%、Al:10.5%~22.5%、B:0%~5.5%、MgO:0%~8%、CaO:0%~9%、SrO:0%~16%、BaO:0%~2.5%、MgO+CaO+SrO+BaO:8%~26%である。
When the alkali-free glass has both a high strain point and a high solubility, it is preferable that SiO 2 : 58% to 66%, Al 2 O 3 : 15% to 22%, expressed by mass% based on oxide. B 2 O 3: 5% ~ 12%, MgO: 0% ~ 8%, CaO: 0% ~ 9%, SrO: 3% ~ 12.5%, BaO: 0% ~ containing 2%, MgO + CaO + SrO + BaO: 9% to 18%.
When it is desired to obtain a particularly high strain point, the alkali-free glass is preferably expressed in terms of mass% 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% to 8%, CaO: 0% to 9%, SrO: 0% to 16%, BaO: 0% to 2.5%, MgO + CaO + SrO + BaO: 8 % To 26%.
 無アルカリガラスの場合、溶融ガラスの粘度が10dPa・s(ポアズ)となる溶融ガラスの温度が1200℃以上である。溶融ガラスの粘度が10dPa・s程度になる場所は、通常、成形工程で用いられるフロートバス10(図1参照)の入口12付近に設定される。フロートバス10の入口12で溶融スズM上に供給された溶融ガラスは、所定方向に流動しながら成形される。 In the case of alkali-free glass, the temperature of the molten glass at which the viscosity of the molten glass is 10 4 dPa · s (poise) is 1200 ° C. or higher. The place where the viscosity of the molten glass is about 10 4 dPa · s is usually set near the inlet 12 of the float bath 10 (see FIG. 1) used in the molding process. The molten glass supplied onto the molten tin M at the inlet 12 of the float bath 10 is molded while flowing in a predetermined direction.
 図1は、本発明の一実施形態によるガラス板の成形工程で用いられるフロートバスの説明図である。 FIG. 1 is an explanatory diagram of a float bath used in a glass plate forming process according to an embodiment of the present invention.
 フロートバス10(以下、単に「バス10」という)は、浴槽22内の溶融スズM上に連続的に供給された溶融ガラスGを、溶融スズM上で流動させて成形する。溶融ガラスGは、バス10の入口12付近で溶融スズM上に供給された後、所定方向に流動しながら冷却され、バス10の出口14付近で溶融スズMから引き上げられる。 Float bath 10 (hereinafter simply referred to as “bath 10”) is formed by causing molten glass G continuously supplied onto molten tin M in bathtub 22 to flow on molten tin M. The molten glass G is supplied onto the molten tin M near the inlet 12 of the bath 10, cooled while flowing in a predetermined direction, and pulled up from the molten tin M near the outlet 14 of the bath 10.
 バス10は、溶融スズMを収容する浴槽22、浴槽22の外周上縁に沿って設置される側壁24、及び側壁24に連結され、浴槽22の上方を覆う天井26などで構成される。天井26には、浴槽22と天井26との間に形成される空間28に還元性ガスを供給するガス供給路30が設けられている。また、ガス供給路30には、加熱源としてのヒータ32が挿通されている。 The bath 10 includes a bathtub 22 that accommodates molten tin M, a side wall 24 that is installed along the outer peripheral upper edge of the bathtub 22, a ceiling 26 that is connected to the side wall 24 and covers the top of the bathtub 22. The ceiling 26 is provided with a gas supply path 30 for supplying a reducing gas to a space 28 formed between the bathtub 22 and the ceiling 26. In addition, a heater 32 as a heating source is inserted into the gas supply path 30.
 ガス供給路30は、溶融スズMの酸化を防止するため、バス10内の空間28に還元性ガスを供給する。還元性ガスは、例えば、水素ガスを1~15体積%、窒素ガスを85~99体積%含んでいる。バス10内の空間28は、側壁24を構成する煉瓦同士の隙間などから大気が混入するのを防止するため、大気圧よりも高い気圧に設定されている。 The gas supply path 30 supplies a reducing gas to the space 28 in the bus 10 in order to prevent the molten tin M from being oxidized. The reducing gas contains, for example, 1 to 15% by volume of hydrogen gas and 85 to 99% by volume of nitrogen gas. The space 28 in the bus 10 is set to a pressure higher than the atmospheric pressure in order to prevent air from being mixed in through a gap between bricks constituting the side wall 24.
 ヒータ32は、バス10内の温度分布を調節するため、例えば、溶融ガラスGの流動方向(X方向)及び幅方向(Y方向)に間隔をおいて複数設けられる。ヒータ32の出力は、バス10の入口12から出口14に向かうほど溶融ガラスGの温度が低くなるように制御される。また、ヒータ32の出力は、溶融ガラスGの厚さが幅方向(Y方向)に均一になるように制御される。 In order to adjust the temperature distribution in the bath 10, a plurality of heaters 32 are provided, for example, at intervals in the flow direction (X direction) and the width direction (Y direction) of the molten glass G. The output of the heater 32 is controlled so that the temperature of the molten glass G decreases as it goes from the inlet 12 to the outlet 14 of the bus 10. The output of the heater 32 is controlled so that the thickness of the molten glass G is uniform in the width direction (Y direction).
 浴槽22は、上方に開放された箱状の金属ケース34、並びに金属ケース34内に設置されるボトム煉瓦36及びサイド煉瓦38で構成される。金属ケース34は、浴槽22内に側方や下方から大気が混入するのを防止する。複数のボトム煉瓦36は、熱膨張によって互いに接触しない程度の僅かな間隔をおいて2次元的に配列されている。複数のボトム煉瓦36は、環状に並ぶ複数のサイド煉瓦38で囲まれている。 The bathtub 22 includes a box-shaped metal case 34 opened upward, and a bottom brick 36 and a side brick 38 installed in the metal case 34. The metal case 34 prevents air from entering the bathtub 22 from the side or from below. The plurality of bottom bricks 36 are two-dimensionally arranged at a slight interval so as not to contact each other due to thermal expansion. The plurality of bottom bricks 36 are surrounded by a plurality of side bricks 38 arranged in a ring shape.
 浴槽22内の溶融スズMは、ヒータ32によって上方から加熱されるので、下方に向かうほど低温になる。そのため、溶融スズMに溶存したガス成分(例えば酸素や水素、水など)は、比較的低温のボトム煉瓦36の上面36aで過飽和析出し、気泡Bを形成する。また、ボトム煉瓦36中を透過したガス(例えば水素など)は、ボトム煉瓦36の上面36aで気泡Bを形成する。 Since the molten tin M in the bathtub 22 is heated from above by the heater 32, the temperature becomes lower as it goes downward. Therefore, gas components (for example, oxygen, hydrogen, water, etc.) dissolved in the molten tin M are supersaturated on the upper surface 36a of the relatively low temperature bottom brick 36 to form bubbles B. Further, gas (for example, hydrogen) that has permeated through the bottom brick 36 forms bubbles B on the upper surface 36 a of the bottom brick 36.
 これらの気泡Bは、ある程度の大きさに成長すると、ボトム煉瓦36の上面36aから離れ、溶融スズMと溶融ガラスGの界面まで浮上し、溶融ガラスGの下面に凹状の欠陥を形成する。その結果、製品であるガラス板の溶融スズMとの接触面(ボトム面)に凹状の欠陥(FOBB)が形成される。 When these bubbles B grow to a certain size, they move away from the upper surface 36a of the bottom brick 36 and rise to the interface between the molten tin M and the molten glass G, and form a concave defect on the lower surface of the molten glass G. As a result, a concave defect (FOBB) is formed on the contact surface (bottom surface) of the glass plate that is the product with the molten tin M.
 本発明者らは、単位時間当たりに生じる気泡Bの総質量が同じ場合、一個一個の気泡Bのサイズが大きくなるほど、気泡Bの数が減ることに着目した。気泡Bがボトム煉瓦36上で大きく成長するためには、ボトム煉瓦36に対する溶融スズMの濡れ性を低くすることが重要である。 The inventors of the present invention focused on the fact that the number of bubbles B decreases as the size of each bubble B increases, when the total mass of bubbles B generated per unit time is the same. In order for the bubbles B to grow greatly on the bottom brick 36, it is important to reduce the wettability of the molten tin M with respect to the bottom brick 36.
 図2は、本発明の一実施形態によるボトム煉瓦に対する溶融スズの濡れ性と、ボトム煉瓦上で形成される気泡の形状との関係を示す図である。図3は、従来のボトム煉瓦に対する溶融スズの濡れ性と、ボトム煉瓦上で形成される気泡の形状との関係を示す図である。図2の本実施形態のボトム煉瓦に対する溶融スズの濡れ性は、図3の従来のボトム煉瓦に対する溶融スズの濡れ性よりも低い。「濡れ性が低い」とはボトム煉瓦に対して溶融スズが濡れにくいことを意味し、「濡れ性が高い」とはボトム煉瓦に対して溶融スズが濡れやすいことを意味する。説明の都合上、濡れ性が高いときの気泡の形状を先に説明する。 FIG. 2 is a diagram showing the relationship between the wettability of molten tin with respect to the bottom brick and the shape of the bubbles formed on the bottom brick according to an embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the wettability of molten tin with respect to a conventional bottom brick and the shape of bubbles formed on the bottom brick. The wettability of molten tin with respect to the bottom brick of the present embodiment of FIG. 2 is lower than the wettability of molten tin with respect to the conventional bottom brick of FIG. “Low wettability” means that molten tin is difficult to wet with respect to the bottom brick, and “high wettability” means that molten tin is easily wetted with respect to the bottom brick. For convenience of explanation, the shape of bubbles when wettability is high will be described first.
 従来、図3に示すように、濡れ性が高いので、ボトム煉瓦6に対する溶融スズMの接触角θ100が小さく、ボトム煉瓦6と気泡B100の接触面積が小さい。そのため、ボトム煉瓦6と気泡B100との間に溶融スズMが入り込もうとするので、気泡B100は大きく成長する前にボトム煉瓦6から離れやすく、小さな気泡B100が多数形成される。 Conventionally, as shown in FIG. 3, since the wettability is high, the contact angle θ100 of the molten tin M with respect to the bottom brick 6 is small, and the contact area between the bottom brick 6 and the bubble B100 is small. Therefore, since the molten tin M tends to enter between the bottom brick 6 and the bubble B100, the bubble B100 is easily separated from the bottom brick 6 before growing large, and many small bubbles B100 are formed.
 一般的に、酸化物に対する溶融金属の濡れ性は低いので、ガラス板の生産開始時にはボトム煉瓦6に対する溶融スズMの濡れ性は低い。しかし、時間の経過に伴って、溶融スズMに不純物として僅かに含まれる酸化スズとボトム煉瓦6とが反応し、反応層(変質層)がボトム煉瓦6の表面に形成されるため、濡れ性が高くなると考えられる。 Generally, since the wettability of the molten metal to the oxide is low, the wettability of the molten tin M to the bottom brick 6 is low at the start of production of the glass plate. However, with the passage of time, tin oxide slightly contained as an impurity in the molten tin M reacts with the bottom brick 6, and a reaction layer (modified layer) is formed on the surface of the bottom brick 6. Will be higher.
 これに対し、本実施形態では、溶融スズMとボトム煉瓦36との反応を抑制するため、各ボトム煉瓦36として、低融点元素の合計の含有量が酸化物換算で20質量%以下の煉瓦を用いる。「低融点元素」は、当該低融点元素の酸化物と、酸化スズ(SnO)との2成分系での共融点が、対応するボトム煉瓦36の上面36aの最高温度よりも低い元素のことである。共融点よりも温度が高くなると、液相が生じるので、低融点元素の酸化物と、酸化スズとの反応が急激に進む。酸化スズは溶融スズMに不純物として微量含まれており、溶融スズM中の酸化スズがボトム煉瓦36中の低融点元素の濃度が高い部分と選択的に反応する。溶融スズM中に含まれる酸化スズは、生産上の理由で側壁24を大気開放するときにバス10内に入り込んだ空気や、側壁24を構成する煉瓦同士の隙間からバス10内に混入した空気に溶融スズMが曝されることで形成される。
  ここで、「低融点元素の合計の含有量」は、低融点元素の数が1つの場合、1つの低融点元素の含有量であり、低融点元素の数が複数の場合、複数の低融点元素の合計の含有量である。
On the other hand, in this embodiment, in order to suppress the reaction between the molten tin M and the bottom brick 36, each bottom brick 36 is a brick whose total content of low melting point elements is 20% by mass or less in terms of oxide. Use. The “low melting point element” is an element whose eutectic point in the binary system of the low melting point element oxide and tin oxide (SnO) is lower than the maximum temperature of the upper surface 36a of the corresponding bottom brick 36. is there. When the temperature becomes higher than the eutectic point, a liquid phase is formed, and the reaction between the oxide of the low melting point element and tin oxide proceeds rapidly. Tin oxide is contained in the molten tin M in a small amount as an impurity, and the tin oxide in the molten tin M selectively reacts with the portion of the bottom brick 36 where the concentration of the low melting point element is high. The tin oxide contained in the molten tin M is air that has entered the bus 10 when the side wall 24 is opened to the atmosphere for production reasons, or air that has entered the bus 10 from the gaps between the bricks constituting the side wall 24. It is formed by exposing molten tin M.
Here, “the total content of low melting point elements” is the content of one low melting point element when the number of low melting point elements is one, and when there are a plurality of low melting point elements, The total content of elements.
 ボトム煉瓦36の上面36aの最高温度はボトム煉瓦36毎に異なる(下流側ほど低い)ので、低融点元素の種類はボトム煉瓦36毎に異なってもよい。バス10の出口14付近では、ボトム煉瓦36aの上面36aの最高温度が低いので、ボトム煉瓦36に低融点元素が存在しなくてもよい。 Since the maximum temperature of the upper surface 36a of the bottom brick 36 is different for each bottom brick 36 (lower downstream side), the kind of the low melting point element may be different for each bottom brick 36. In the vicinity of the outlet 14 of the bath 10, since the maximum temperature of the upper surface 36 a of the bottom brick 36 a is low, the low melting point element may not be present in the bottom brick 36.
 低融点元素としては、例えばケイ素(Si)などが挙げられる。ケイ素の酸化物(SiO)と、酸化スズとの共融点は、850℃程度であり、大部分のボトム煉瓦36の上面36aの最高温度よりも低い。 Examples of the low melting point element include silicon (Si). The eutectic point of silicon oxide (SiO 2 ) and tin oxide is about 850 ° C., which is lower than the maximum temperature of the upper surface 36 a of most bottom bricks 36.
 本実施形態では、各ボトム煉瓦36において、低融点元素の合計の含有量が酸化物換算で20質量%以下(好ましくは15質量%以下、より好ましくは10質量%以下)であるので、各ボトム煉瓦36と溶融スズMとがほとんど反応しない。低融点元素の合計の含有量が酸化物換算で20質量%以下であれば、低融点元素の大部分はボトム煉瓦36中のその他の元素と酸化物を構成しており、当該酸化物の融点はボトム煉瓦36の上面36aの最高温度よりも高いからである。各ボトム煉瓦36と溶融スズMとがほとんど反応しないので、ガラス板の生産開始から時間が経過したときも、各ボトム煉瓦36に対する溶融スズMの濡れ性が低い。
  尚、本実施形態では各ボトム煉瓦36において低融点元素の合計の含有量が酸化物換算で20質量%以下であるが、全てのボトム煉瓦36において低融点元素の合計の含有量が酸化物換算で20質量%以下でなくてもよい。ボトムレンガの上面の最高温度が、溶融ガラスGの粘度が10dPa・sとなる溶融ガラスGの温度以下であり且つ低融点元素の酸化物と酸化スズとの2成分系での共融点を超える温度である、少なくとも1つのボトム煉瓦は、低融点元素の合計の含有量が酸化物換算で20質量%以下であればよく、0質量%を超えてもよい。
In the present embodiment, in each bottom brick 36, the total content of the low melting point elements is 20% by mass or less (preferably 15% by mass or less, more preferably 10% by mass or less) in terms of oxide. The brick 36 and the molten tin M hardly react. If the total content of the low melting point elements is 20% by mass or less in terms of oxide, most of the low melting point elements constitute oxides with other elements in the bottom brick 36, and the melting point of the oxides. This is because the temperature is higher than the maximum temperature of the upper surface 36 a of the bottom brick 36. Since each bottom brick 36 and molten tin M hardly react, the wettability of molten tin M with respect to each bottom brick 36 is low even when time elapses from the start of glass plate production.
In this embodiment, the total content of low melting point elements in each bottom brick 36 is 20% by mass or less in terms of oxides, but the total content of low melting point elements in all bottom bricks 36 is in terms of oxides. It may not be 20 mass% or less. The maximum temperature of the upper surface of the bottom brick is equal to or lower than the temperature of the molten glass G at which the viscosity of the molten glass G is 10 4 dPa · s, and the eutectic point in the binary system of the low melting point element oxide and tin oxide The total content of the low melting point elements may be 20% by mass or less in terms of oxide, and may exceed 0% by mass, at least one bottom brick having a temperature exceeding.
 各ボトム煉瓦36に対する溶融スズMの濡れ性が低いので、図2に示すように、ボトム煉瓦36に対する溶融スズMの接触角θが大きく、ボトム煉瓦36と気泡Bの接触面積が大きい。そのため、ボトム煉瓦6と気泡Bとの間に溶融スズMが入り込みにくく、気泡Bは大きく成長するまでボトム煉瓦36から離れない。 Since the wettability of the molten tin M with respect to each bottom brick 36 is low, as shown in FIG. 2, the contact angle θ of the molten tin M with respect to the bottom brick 36 is large, and the contact area between the bottom brick 36 and the bubbles B is large. Therefore, molten tin M is difficult to enter between the bottom brick 6 and the bubbles B, and the bubbles B do not leave the bottom brick 36 until they grow large.
 このように、本実施形態によれば、一個一個の気泡Bのサイズが大きくなるので、単位時間当たりに生じる気泡Bの総質量が同じ場合、単位時間当たりに生じる気泡Bの数が減る。その結果、ガラス板のボトム面に形成されるFOBBの数が減り、FOBBがガラス板の歩留まりが上がる。この効果は、下記の(1)~(2)の理由で、ガラス板のガラスが無アルカリガラスの場合に顕著に得られる。
(1)無アルカリガラスは、一般的なソーダライムガラスに比べて、溶融ガラスGの成形温度が高く、ボトム煉瓦36の上面36aの温度が高い。そのため、ボトム煉瓦36の化学組成が同じ場合、ボトム煉瓦36と溶融スズMとの反応が進みやすい。
(2)無アルカリガラスは、ソーダライムガラスと異なり、アルカリ金属元素(例えばNa、K)を実質的に含まないため、ボトム煉瓦36のネフェリン((Na,K)AlSiO)化がほとんど起きない。ネフェリン化は、ボトム煉瓦36上に緻密なガラス層を形成し、ボトム煉瓦36の内部から上面36aへのガスの透過を抑制する。無アルカリガラスでは、ネフェリン化がほとんど起きないので、単位時間当たりに生じる気泡Bの総質量が多くなる。
Thus, according to this embodiment, since the size of each bubble B increases, if the total mass of bubbles B generated per unit time is the same, the number of bubbles B generated per unit time decreases. As a result, the number of FOBBs formed on the bottom surface of the glass plate is reduced, and the yield of FOBB is increased. This effect is remarkably obtained when the glass of the glass plate is non-alkali glass for the following reasons (1) to (2).
(1) The alkali-free glass has a higher molding temperature of the molten glass G and a higher temperature of the upper surface 36a of the bottom brick 36 than a general soda lime glass. Therefore, when the chemical composition of the bottom brick 36 is the same, the reaction between the bottom brick 36 and the molten tin M is likely to proceed.
(2) Unlike alkali soda lime glass, alkali-free glass does not substantially contain alkali metal elements (for example, Na, K), so that the bottom brick 36 is hardly converted to nepheline ((Na, K) AlSiO 4 ). . Nephelinization forms a dense glass layer on the bottom brick 36 and suppresses gas permeation from the inside of the bottom brick 36 to the upper surface 36a. In alkali-free glass, nephelinization hardly occurs, so that the total mass of bubbles B generated per unit time increases.
 また、本実施形態では、上述の如く、各ボトム煉瓦36と溶融スズMとがほとんど反応しないので、ボトム煉瓦36の上面36aの変質が抑えられ、変質した粒子の脱離が抑制される。脱離した粒子は溶融スズMと溶融ガラスGとの界面まで浮上することにより溶融ガラスGの欠点となるので、粒子の脱離を抑制することで、ガラス板の品質を向上することができる。 In the present embodiment, as described above, the bottom bricks 36 and the molten tin M hardly react with each other, so that the alteration of the upper surface 36a of the bottom brick 36 is suppressed, and the detachment of the altered particles is suppressed. Since the desorbed particles float up to the interface between the molten tin M and the molten glass G and become a defect of the molten glass G, the quality of the glass plate can be improved by suppressing the desorption of the particles.
 ボトム煉瓦36としては、例えば、アルミナ(Al)-カルシア(CaO)系煉瓦、又はアルミナ(Al)-ジルコニア(ZrO)系煉瓦等の粘度質焼成煉瓦が用いられる。粘度質焼成煉瓦では、焼結助剤としてSiO等が用いられており、SiO濃度の高い部分がある。 As the bottom brick 36, for example, a viscous fired brick such as alumina (Al 2 O 3 ) -calcia (CaO) brick or alumina (Al 2 O 3 ) -zirconia (ZrO 2 ) brick is used. In the viscous fired brick, SiO 2 or the like is used as a sintering aid, and there is a portion having a high SiO 2 concentration.
 アルミナ-カルシア系煉瓦は、例えば、酸化物基準の質量%表示で、Al:40%~85%、CaO:10%~40%、SiO:0.5%~20%含有する。SiO含有量は、好ましくは15質量%以下、より好ましくは10質量%以下、さらに好ましくは7質量%以下、特に好ましくは3質量%以下、さらに特に好ましくは1質量%以下である。 The alumina-calcia brick contains, for example, Al 2 O 3 : 40% to 85%, CaO: 10% to 40%, and SiO 2 : 0.5% to 20% in terms of mass% based on oxide. The SiO 2 content is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 7% by mass or less, particularly preferably 3% by mass or less, and even more preferably 1% by mass or less.
 アルミナ-ジルコニア系煉瓦は、例えば、酸化物基準の質量%表示で、Al:40%~55%、ZrO:30%~45%、SiO:0.5%~20%含有する。SiO含有量は、好ましくは15質量%以下、より好ましくは10質量%以下、さらに好ましくは7質量%以下、特に好ましくは3質量%以下、さらに特に好ましくは1質量%以下である。 Alumina-zirconia bricks contain, for example, Al 2 O 3 : 40% to 55%, ZrO 2 : 30% to 45%, SiO 2 : 0.5% to 20% in terms of mass% based on oxide. . The SiO 2 content is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 7% by mass or less, particularly preferably 3% by mass or less, and even more preferably 1% by mass or less.
 サイド煉瓦38は、ボトム煉瓦36と同様に、低融点元素の合計の含有量が酸化物換算で20質量%以下であってもよいし、20質量%を超えてもよい。成形時に溶融ガラスGはサイド煉瓦38よりも内側にあるので、サイド煉瓦38の内壁面で形成される気泡はFOBBの原因にならない。 The side brick 38 may have a total content of low melting point elements of 20% by mass or less in terms of oxide, or may exceed 20% by mass, as with the bottom brick 36. Since the molten glass G is inside the side brick 38 at the time of molding, the bubbles formed on the inner wall surface of the side brick 38 do not cause FOBB.
 尚、上記実施形態のガラス板は、液晶ディスプレイの基板として用いられるが、用途は多種多様であってよい。例えば、ガラス板は、有機ELディスプレイの基板、タッチパネルのカバーガラスとして用いられてもよい。 In addition, although the glass plate of the said embodiment is used as a board | substrate of a liquid crystal display, a use may be various. For example, the glass plate may be used as a substrate for an organic EL display or a cover glass for a touch panel.
 以下に、実施例等により本発明を具体的に説明する。 Hereinafter, the present invention will be specifically described with reference to examples and the like.
 [実施例1]
 先ず、煉瓦を加工してルツボを用意し、用意したルツボ内に金属スズを入れ、電気炉内に設置し、電気炉内の雰囲気を置換した後、1000℃で60分間、金属スズを溶融させ、溶融スズとルツボとの反応性を調べた。
[Example 1]
First, a brick is processed to prepare a crucible, and metal tin is put into the prepared crucible, installed in an electric furnace, the atmosphere in the electric furnace is replaced, and then the metal tin is melted at 1000 ° C. for 60 minutes. The reactivity between molten tin and crucible was investigated.
 煉瓦としては、アルミナ(Al)-カルシア(CaO)系煉瓦である煉瓦Aを用意した。煉瓦Aは、酸化物基準の質量%表示で、SiO:5.7%、Al:66.0%、CaO:26.0%、MgO:1.5%、NaO:0.3%、Fe:0.1%を含有しており、その他の成分はそれぞれ0.1%未満である。煉瓦Aの化学組成は、蛍光X線分析装置(理学電気工業株式会社製、ZSX100e)により測定した。 As the brick, brick A, which is an alumina (Al 2 O 3 ) -calcia (CaO) brick, was prepared. Brick A is expressed in terms of mass% on an oxide basis, SiO 2 : 5.7%, Al 2 O 3 : 66.0%, CaO: 26.0%, MgO: 1.5%, Na 2 O: 0. .3%, Fe 2 O 3 : 0.1%, and other components are each less than 0.1%. The chemical composition of the brick A was measured with a fluorescent X-ray analyzer (manufactured by Rigaku Denki Kogyo Co., Ltd., ZSX100e).
 ルツボは、有底の円筒形状(内径6mm、内寸高さ6mm、底壁の厚さ3mm、側壁の厚さ2mm)に加工した。 The crucible was processed into a bottomed cylindrical shape (inner diameter 6 mm, inner dimension height 6 mm, bottom wall thickness 3 mm, side wall thickness 2 mm).
 金属スズには、純度が99.95質量%のもの(関東化学社製、特級)を用いた。金属スズは、溶融スズの厚さが5mmとなるように秤量し、ルツボ内に入れた。 Metal tin with a purity of 99.95% by mass (manufactured by Kanto Chemical Co., Ltd., special grade) was used. Metal tin was weighed so that the thickness of molten tin was 5 mm and placed in a crucible.
 電気炉内の雰囲気は、真空ポンプで電気炉内を1kPaに真空引きした後、ガス供給管を介して電気炉内にガスを供給して置換した。ガスとしては、酸素濃度が1000体積ppmの窒素ガスを用いた。窒素ガスを用いたのは、窒素ガスは酸素ガスとの反応性が低く、酸素濃度に影響を及ぼさないためである。 The atmosphere in the electric furnace was replaced by evacuating the electric furnace to 1 kPa with a vacuum pump and then supplying gas into the electric furnace through a gas supply pipe. As the gas, nitrogen gas with an oxygen concentration of 1000 ppm by volume was used. Nitrogen gas was used because nitrogen gas has low reactivity with oxygen gas and does not affect the oxygen concentration.
 溶融スズとルツボとの反応性は、室温まで冷却したルツボを樹脂で固化させた後に切断し、切断面をSEM(Scanning Electron Microscope、キーエンス社製、VE-9800)で観察して調べた。 The reactivity between the molten tin and the crucible was examined by solidifying the crucible cooled to room temperature with a resin and then cutting it, and observing the cut surface with an SEM (Scanning Electron Microscope, manufactured by Keyence Corporation, VE-9800).
 図4は、実施例1によるルツボの切断面のSEM写真を示す。図4から明らかなように、ルツボ41の内底面には、溶融スズ44との反応層が見られなかった。また、ルツボ41と溶融スズ44との間に部分的に隙間45が形成されており、ルツボ41に対する溶融スズ44の濡れ性が低いことがわかる。 FIG. 4 shows an SEM photograph of the cut surface of the crucible according to Example 1. As apparent from FIG. 4, no reaction layer with molten tin 44 was observed on the inner bottom surface of the crucible 41. Further, a gap 45 is partially formed between the crucible 41 and the molten tin 44, and it can be seen that the wettability of the molten tin 44 with respect to the crucible 41 is low.
 図5は、実施例1における評価用ガラスに形成される欠陥の数を調べる試験を示す。この試験では、煉瓦Aを加工したルツボ51を用意し、用意したルツボ51内に金属スズを入れ、カーボン冶具52に評価用ガラス53を載せた。続いて、グローブボックスの電気炉内にルツボ51を設置し、電気炉内の雰囲気を置換した後、電気炉内の温度を上げ、評価用ガラス53を自重で熱変形させて溶融スズ54上に載せた。次いで、電気炉内の温度を1100℃で10分間保持した後、電気炉内の温度を800℃に下げ、固化した評価用ガラス53を手動で溶融スズ54から引き上げた。続いて、電気炉内で評価用ガラス53を徐冷し、評価用ガラス53の溶融スズ54と接触した部分に形成されたFOBBの数を調べた。 FIG. 5 shows a test for examining the number of defects formed in the glass for evaluation in Example 1. In this test, a crucible 51 in which brick A was processed was prepared, metal tin was put into the prepared crucible 51, and an evaluation glass 53 was placed on a carbon jig 52. Subsequently, the crucible 51 is installed in the electric furnace of the glove box, the atmosphere in the electric furnace is replaced, the temperature in the electric furnace is increased, and the evaluation glass 53 is thermally deformed by its own weight to be formed on the molten tin 54. I put it. Next, after maintaining the temperature in the electric furnace at 1100 ° C. for 10 minutes, the temperature in the electric furnace was lowered to 800 ° C., and the solidified evaluation glass 53 was manually pulled up from the molten tin 54. Subsequently, the glass for evaluation 53 was gradually cooled in an electric furnace, and the number of FOBBs formed in the portion of the glass for evaluation 53 in contact with the molten tin 54 was examined.
 ルツボ51は、有底の円筒形状(内径60mm、内寸高さ40mm、底壁の厚さ10mm、側壁の厚さ10mm)に加工した。 The crucible 51 was processed into a bottomed cylindrical shape (inner diameter 60 mm, inner dimension height 40 mm, bottom wall thickness 10 mm, side wall thickness 10 mm).
 金属スズには、純度が99.95質量%のもの(関東化学社製、特級)を用いた。金属スズは、溶融スズの厚さが20mmとなるように秤量し、ルツボ内に入れた。 Metal tin with a purity of 99.95% by mass (manufactured by Kanto Chemical Co., Ltd., special grade) was used. Metal tin was weighed so that the thickness of molten tin was 20 mm and placed in a crucible.
 評価用ガラス53としては、無アルカリガラス板(縦40mm、横40mm、厚さ0.7mm)を用意した。この無アルカリガラス板は、酸化物基準の質量%表示で、SiO:60.0%、Al:17.0%、B:8.0%、MgO:3.0%、CaO:4.5%、SrO:7.5%を含有していた。ガラス板の化学組成は、蛍光X線分析装置(理学電気工業株式会社製、ZSX100e)により測定した。 As the glass 53 for evaluation, the alkali free glass plate (length 40mm, width 40mm, thickness 0.7mm) was prepared. This non-alkali glass plate is expressed in terms of mass% based on oxide, SiO 2 : 60.0%, Al 2 O 3 : 17.0%, B 2 O 3 : 8.0%, MgO: 3.0% CaO: 4.5% and SrO: 7.5%. The chemical composition of the glass plate was measured with a fluorescent X-ray analyzer (manufactured by Rigaku Denki Kogyo Co., Ltd., ZSX100e).
 電気炉内の雰囲気は、真空ポンプで電気炉内を1kPaに真空引きした後、ガス供給管を介して電気炉内にガスを供給して置換した。ガスとしては、水素濃度が10体積%の窒素ガスを用いた。 The atmosphere in the electric furnace was replaced by evacuating the electric furnace to 1 kPa with a vacuum pump and then supplying gas into the electric furnace through a gas supply pipe. As the gas, nitrogen gas having a hydrogen concentration of 10% by volume was used.
 評価用ガラス53に形成された欠陥(FOBB)の数は、評価用ガラス53を室温まで冷却した後、評価用ガラス53の溶融スズ54と接触した部分(5mm×5mm)を光学顕微鏡で観察して調べた。大きな欠陥(直径300μm超)の数は0個であり、小さな欠陥(直径10~300μm)の数は2個であった。また、小さな欠陥の数と大きな欠陥の数との総数は、後述の比較例1の場合に比べて10%以下であった。 The number of defects (FOBB) formed in the glass for evaluation 53 was measured by cooling the glass for evaluation 53 to room temperature, and then observing the portion (5 mm × 5 mm) in contact with the molten tin 54 of the glass for evaluation 53 with an optical microscope. I investigated. The number of large defects (diameter over 300 μm) was 0, and the number of small defects (diameter 10 to 300 μm) was 2. The total number of small defects and large defects was 10% or less as compared with the case of Comparative Example 1 described later.
 欠陥の数が少ない理由は、ルツボ51の材料である煉瓦Aは低融点元素であるSiの含有量が少ないためと推定される。Siの含有量が少ないため、図4に示すようにルツボ41と溶融スズ44とがほとんど反応しておらず、ルツボ41に対する溶融スズ44の濡れ性が低い。濡れ性が低いので、図3に示すようにルツボの内底面上で形成される気泡が浮上しにくく、気泡が保持されたまま大きく成長し、その結果、小さい欠陥の数が少ない。 It is estimated that the reason for the small number of defects is that the brick A, which is the material of the crucible 51, has a low content of Si, which is a low melting point element. Since the Si content is small, the crucible 41 and the molten tin 44 hardly react as shown in FIG. 4, and the wettability of the molten tin 44 with respect to the crucible 41 is low. Since the wettability is low, as shown in FIG. 3, the bubbles formed on the inner bottom surface of the crucible do not easily float and grow large while retaining the bubbles, and as a result, the number of small defects is small.
 [実施例2]
 実施例2では、アルミナ(Al)-カルシア(CaO)系煉瓦である煉瓦Bを用意し、実施例1と同様にして、評価用ガラスに形成される欠陥の数を調べた。煉瓦Bは、酸化物基準の質量%表示で、SiO:5.8%、Al:82.4%、CaO:10.2%、MgO:1.2%、NaO:0.2%、Fe:0.2%、その他の成分はそれぞれ0.1%未満である。
[Example 2]
In Example 2, brick B, which is an alumina (Al 2 O 3 ) -calcia (CaO) brick, was prepared, and the number of defects formed in the evaluation glass was examined in the same manner as in Example 1. Brick B is expressed in terms of mass% based on oxide, SiO 2 : 5.8%, Al 2 O 3 : 82.4%, CaO: 10.2%, MgO: 1.2%, Na 2 O: 0 0.2%, Fe 2 O 3 : 0.2%, and other components are each less than 0.1%.
 大きな欠陥(直径300μm超)の数は0個であり、小さな欠陥(直径10~300μm)の数は10個以下である。 The number of large defects (diameter over 300 μm) is 0, and the number of small defects (diameter 10 to 300 μm) is 10 or less.
 [実施例3]
 実施例3では、アルミナ(Al)-ジルコニア(ZrO)系煉瓦である煉瓦Cを用意した他は、実施例1と同様にして、評価用ガラスに形成される欠陥の数を調べた。煉瓦Cは、酸化物基準の質量%表示で、SiO:13.5%、ZrO:33.0%、Al:52.0%、NaO:1.3%を含有しており、その他の成分はそれぞれ0.1%未満である。
[Example 3]
In Example 3, the number of defects formed in the glass for evaluation was examined in the same manner as in Example 1 except that brick C, which is an alumina (Al 2 O 3 ) -zirconia (ZrO 2 ) -based brick, was prepared. It was. Brick C contains SiO 2 : 13.5%, ZrO 2 : 33.0%, Al 2 O 3 : 52.0%, Na 2 O: 1.3% in terms of mass% based on oxide. The other components are each less than 0.1%.
 大きな欠陥(直径300μm超)の数は0個であり、小さな欠陥(直径10~300μm)の数は15個である。 The number of large defects (diameter over 300 μm) is 0, and the number of small defects (diameter 10 to 300 μm) is 15.
 [比較例1]
 比較例1では、アルミナ(Al)-シリカ(SiO)系煉瓦である煉瓦Dを用意した他は、実施例1と同様にして煉瓦と溶融スズとの反応性を調べた。煉瓦Dは、酸化物基準の質量%表示で、SiO:58.0%、Al:37.0%、CaO:0.4%、MgO:0.1%、P:0.4%、NaO:0.1%、KO:0.9%、Fe:1.2%、TiO:0.9%、ZrO:0.1%を含有しており、その他の成分はそれぞれ0.1%未満である。
[Comparative Example 1]
In Comparative Example 1, the reactivity between brick and molten tin was examined in the same manner as in Example 1 except that brick D, which is an alumina (Al 2 O 3 ) -silica (SiO 2 ) brick, was prepared. Brick D is expressed in terms of mass% based on oxide, SiO 2 : 58.0%, Al 2 O 3 : 37.0%, CaO: 0.4%, MgO: 0.1%, P 2 O 5 : Contains 0.4%, Na 2 O: 0.1%, K 2 O: 0.9%, Fe 2 O 3 : 1.2%, TiO 2 : 0.9%, ZrO 2 : 0.1% The other components are each less than 0.1%.
 図6は、比較例1によるルツボの切断面のSEM写真を示す。図7は、図6の一部を拡大したSEM写真を示す。図6および図7から明らかなように、ルツボ61の内底部に溶融スズ64との反応層66が見られた。また、ルツボ61と溶融スズ64とが密着しており、ルツボ61に対する溶融スズ64の濡れ性が高いことがわかる。 FIG. 6 shows a SEM photograph of the cut surface of the crucible according to Comparative Example 1. FIG. 7 shows an SEM photograph in which a part of FIG. 6 is enlarged. As is clear from FIGS. 6 and 7, a reaction layer 66 with molten tin 64 was found on the inner bottom of the crucible 61. Further, it is understood that the crucible 61 and the molten tin 64 are in close contact with each other, and the wettability of the molten tin 64 with respect to the crucible 61 is high.
 図8は図7のSEM写真と同じ領域をEDSで元素分析したSn元素のマップ、図9は図7のSEM写真と同じ領域をEDSで元素分析したAl元素のマップ、図10は図7のSEM写真と同じ領域をEDSで元素分析したSi元素のマップを示す。図8~図10において、輝度が高い部分ほど、元素濃度が高いことを表す。EDS(Energy Dispersive X-ray Spectrometry)としては、上記のSEMに付属のものを用いた。 8 is a map of Sn element obtained by elemental analysis of the same region as the SEM photograph of FIG. 7 by EDS, FIG. 9 is a map of Al element obtained by elemental analysis of the same region as the SEM photograph of FIG. 7 by EDS, and FIG. A map of Si element obtained by elemental analysis of the same region as the SEM photograph by EDS is shown. 8 to 10, the higher the luminance, the higher the element concentration. As EDS (Energy Dispersive X-ray Spectrometry), the one attached to the SEM was used.
 図8~図10から明らかなように、ルツボ61の内底部のうち、Alが少なく、Siが多い部分67でSnが増えていることがわかる。これは、溶融スズ64がルツボ61中のSi濃度の高い部分と選択的に反応していることを示している。 As is apparent from FIGS. 8 to 10, it can be seen that Sn is increased in a portion 67 having a small amount of Al and a large amount of Si in the inner bottom portion of the crucible 61. This indicates that the molten tin 64 is selectively reacting with a portion having a high Si concentration in the crucible 61.
 また、比較例1では、煉瓦として上記煉瓦Dを使用した他は、実施例1と同様にして、評価用ガラスに形成される欠陥の数を調べた。その結果、大きな欠陥(直径300μm超)の数は0個であり、小さな欠陥(直径10~300μm)の数は60個であった。 In Comparative Example 1, the number of defects formed in the glass for evaluation was examined in the same manner as in Example 1 except that the brick D was used as a brick. As a result, the number of large defects (diameter exceeding 300 μm) was 0, and the number of small defects (diameter 10 to 300 μm) was 60.
 欠陥の数が多い理由は、ルツボの材料である煉瓦Dは低融点元素であるSiの含有量が多いためと推定される。Siの含有量が多いため、図6及び図7に示すようにルツボ61に溶融スズ64との反応層66が形成され、ルツボ61に対する溶融スズ64の濡れ性が高い。濡れ性が高いので、図2に示すようにルツボの内底面上で形成される気泡が小さい状態で浮上し、その結果、小さい欠陥の数が多い。 It is presumed that the reason for the large number of defects is that the brick D, which is a material for the crucible, has a high content of Si, which is a low melting point element. Since the Si content is large, a reaction layer 66 with molten tin 64 is formed on the crucible 61 as shown in FIGS. 6 and 7, and the wettability of the molten tin 64 with respect to the crucible 61 is high. Since the wettability is high, the bubbles formed on the inner bottom surface of the crucible float in a small state as shown in FIG. 2, and as a result, the number of small defects is large.
 [比較例2]
 比較例2では、アルミナ(Al)-シリカ(SiO)系煉瓦である煉瓦Eを用意し、比較例1と同様にして評価用ガラスに形成される欠陥の数を調べた。煉瓦Eは、酸化物基準の質量%表示で、SiO:58.0%、Al:37.0%、CaO:0.2%、MgO:0.3%、NaO:0.8%、KO:0.9%、Fe:1.1%、TiO:1.6%、その他の成分はそれぞれ0.1%未満である。
[Comparative Example 2]
In Comparative Example 2, brick E, which is an alumina (Al 2 O 3 ) -silica (SiO 2 ) brick, was prepared, and the number of defects formed in the evaluation glass was examined in the same manner as in Comparative Example 1. Brick E is expressed in terms of mass% based on oxide, SiO 2 : 58.0%, Al 2 O 3 : 37.0%, CaO: 0.2%, MgO: 0.3%, Na 2 O: 0 0.8%, K 2 O: 0.9%, Fe 2 O 3 : 1.1%, TiO 2 : 1.6%, and other components are each less than 0.1%.
 その結果、大きな欠陥(直径300μm超)の数は0個であり、小さな欠陥(直径10~300μm)の数は70個であった。 As a result, the number of large defects (diameter exceeding 300 μm) was 0, and the number of small defects (diameter 10 to 300 μm) was 70.
 [参考例1]
 参考例1では、真空引きした後の電気炉内に供給するガスとして、10体積%の水素ガス、及び90体積%の窒素ガスからなる還元性ガスを用いた他は、比較例1と同様にして煉瓦Dと溶融スズとの反応性を調べた。
[Reference Example 1]
Reference Example 1 was the same as Comparative Example 1 except that a reducing gas composed of 10% by volume hydrogen gas and 90% by volume nitrogen gas was used as the gas supplied into the electric furnace after evacuation. The reactivity between brick D and molten tin was investigated.
 図11に参考例1によるルツボの切断面のSEM写真を示す。図11から明らかなように、ルツボ71に溶融スズ74との反応層が見られなかった。また、ルツボ71と溶融スズ74との間に部分的に隙間75が形成されており、ルツボ71に対する溶融スズ74の濡れ性が低いことがわかる。 FIG. 11 shows an SEM photograph of the cut surface of the crucible according to Reference Example 1. As is clear from FIG. 11, no reaction layer with molten tin 74 was observed in the crucible 71. Further, a gap 75 is partially formed between the crucible 71 and the molten tin 74, and it can be seen that the wettability of the molten tin 74 with respect to the crucible 71 is low.
 参考例1の結果と、比較例1の結果から、溶融スズ74上の雰囲気中に含まれる微量の酸素ガスが、煉瓦と溶融スズとの濡れ性に影響を及ぼすことがわかる。酸素ガスが溶融スズ中に溶け込み、溶融スズ中のSnO成分がルツボ71のSiO成分と反応し、反応層が形成されると、濡れ性が高くなる。 From the result of Reference Example 1 and the result of Comparative Example 1, it can be seen that a small amount of oxygen gas contained in the atmosphere on the molten tin 74 affects the wettability between the brick and the molten tin. When oxygen gas dissolves in the molten tin and the SnO component in the molten tin reacts with the SiO 2 component of the crucible 71 to form a reaction layer, the wettability increases.
 実施例1~3、比較例1、2の評価の結果を表1に示す。表1において煉瓦の組成は、SiO、Al、CaO、MgO、およびZrOのみ示す。 The evaluation results of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1. In Table 1, the composition of bricks is shown only for SiO 2 , Al 2 O 3 , CaO, MgO, and ZrO 2 .
Figure JPOXMLDOC01-appb-T000001
 以上、ガラス板の製造方法を実施形態および実施例等で説明したが、本発明は上記実施形態および実施例等に限定されない。特許請求の範囲に記載された本発明の要旨の範囲内において、種々の変形、改良が可能である。
Figure JPOXMLDOC01-appb-T000001
As mentioned above, although the manufacturing method of the glass plate was demonstrated by embodiment, the Example, etc., this invention is not limited to the said embodiment, Example, etc. Various modifications and improvements can be made within the scope of the gist of the present invention described in the claims.
 本出願は、2012年3月27日に日本国特許庁に出願された特願2012-072495号に基づく優先権を主張するものであり、特願2012-072495号の全内容を本国際出願に援用する。 This application claims priority based on Japanese Patent Application No. 2012-072495 filed with the Japan Patent Office on March 27, 2012. The entire contents of Japanese Patent Application No. 2012-072495 are incorporated herein by reference. Incorporate.
10 フロートバス
12 フロートバスの入口
14 フロートバスの出口
22 浴槽
24 側壁
26 天井
28 空間
30 ガス供給路
32 ヒータ
34 金属ケース
36 ボトム煉瓦
38 サイド煉瓦
M  溶融スズ
G  溶融ガラス
DESCRIPTION OF SYMBOLS 10 Float bath 12 Float bath inlet 14 Float bath outlet 22 Bathtub 24 Side wall 26 Ceiling 28 Space 30 Gas supply path 32 Heater 34 Metal case 36 Bottom brick 38 Side brick M Molten tin G Molten glass

Claims (7)

  1.  浴槽内の溶融スズ上に連続的に供給される溶融ガラスを前記溶融スズ上で流動させて成形する工程を有するガラス板の製造方法において、
     前記ガラス板のガラスは無アルカリガラスであって、前記溶融ガラスの粘度が10dPa・sとなる前記溶融ガラスの温度が1200℃以上であり、
     前記浴槽の各ボトム煉瓦は、低融点元素の合計の含有量が酸化物換算で20質量%以下であって、
     前記低融点元素は、該低融点元素の酸化物と、酸化スズ(SnO)との2成分系での共融点が、対応する前記ボトム煉瓦の上面の最高温度よりも低い元素のことである、ガラス板の製造方法。
    In the method for producing a glass plate, the method includes a step of forming molten glass that is continuously supplied onto molten tin in a bath and flowing on the molten tin.
    The glass of the glass plate is alkali-free glass, and the temperature of the molten glass at which the viscosity of the molten glass is 10 4 dPa · s is 1200 ° C. or higher,
    Each bottom brick of the bathtub has a total content of low melting point elements of 20% by mass or less in terms of oxide,
    The low melting point element is an element having an eutectic point in a binary system of an oxide of the low melting point element and tin oxide (SnO) lower than the maximum temperature of the upper surface of the corresponding bottom brick. Manufacturing method of glass plate.
  2.  浴槽内の溶融スズ上に連続的に供給される溶融ガラスを前記溶融スズ上で流動させて成形する工程を有するガラス板の製造方法において、
     前記ガラス板のガラスは無アルカリガラスであって、前記溶融ガラスの粘度が10dPa・sとなる前記溶融ガラスの温度が1200℃以上であり、
     前記浴槽はボトム煉瓦を含み、
     ボトム煉瓦の上面の最高温度が、前記溶融ガラスの粘度が10dPa・sとなる前記溶融ガラスの温度以下であり且つ低融点元素の酸化物と酸化スズ(SnO)との2成分系での共融点を超える温度である、少なくとも1つのボトム煉瓦は、低融点元素の合計の含有量が酸化物換算で20質量%以下であって、
     前記低融点元素は、該低融点元素の酸化物と、酸化スズ(SnO)との2成分系での共融点が、対応する前記ボトム煉瓦の上面の最高温度よりも低い元素のことである、ガラス板の製造方法。
    In the method for producing a glass plate, the method includes a step of forming molten glass that is continuously supplied onto molten tin in a bath and flowing on the molten tin.
    The glass of the glass plate is alkali-free glass, and the temperature of the molten glass at which the viscosity of the molten glass is 10 4 dPa · s is 1200 ° C. or higher,
    The bathtub includes a bottom brick;
    The maximum temperature of the upper surface of the bottom brick is equal to or lower than the temperature of the molten glass at which the viscosity of the molten glass is 10 4 dPa · s, and is a two-component system of an oxide of a low melting point element and tin oxide (SnO) At least one bottom brick having a temperature exceeding the eutectic point has a total content of low melting point elements of 20% by mass or less in terms of oxide,
    The low melting point element is an element having an eutectic point in a binary system of an oxide of the low melting point element and tin oxide (SnO) lower than the maximum temperature of the upper surface of the corresponding bottom brick. Manufacturing method of glass plate.
  3.  前記低融点元素は、ケイ素(Si)である請求項1又は2に記載のガラス板の製造方法。 The method for producing a glass plate according to claim 1 or 2, wherein the low melting point element is silicon (Si).
  4.  前記ボトム煉瓦は、アルミナ(Al)-カルシア(CaO)系煉瓦、又はアルミナ(Al)-ジルコニア(ZrO)系煉瓦である請求項1~3のいずれか1項に記載のガラス板の製造方法。 The bottom brick is an alumina (Al 2 O 3 ) -calcia (CaO) brick or an alumina (Al 2 O 3 ) -zirconia (ZrO 2 ) brick. Manufacturing method of glass plate.
  5.  前記無アルカリガラスは、酸化物基準の質量%表示で、SiO:50%~73%、Al:10.5%~24%、B:0%~12%、MgO:0%~8%、CaO:0%~14.5%、SrO:0%~24%、BaO:0%~13.5%、ZrO:0%~5%を含有し、MgO+CaO+SrO+BaO:8%~29.5%である請求項1~4のいずれか1項に記載のガラス板の製造方法。 The alkali-free glass is expressed in terms of mass% based on oxide, SiO 2 : 50% to 73%, Al 2 O 3 : 10.5% to 24%, B 2 O 3 : 0% to 12%, MgO: 0% to 8%, CaO: 0% to 14.5%, SrO: 0% to 24%, BaO: 0% to 13.5%, ZrO 2 : 0% to 5%, MgO + CaO + SrO + BaO: 8% The method for producing a glass plate according to any one of claims 1 to 4, wherein the content is from 2 to 29.5%.
  6.  前記無アルカリガラスは、酸化物基準の質量%表示で、SiO:58%~66%、Al:15%~22%、B:5%~12%、MgO:0%~8%、CaO:0%~9%、SrO:3%~12.5%、BaO:0%~2%を含有し、MgO+CaO+SrO+BaO:9%~18%である請求項5に記載のガラス板の製造方法。 The alkali-free glass is expressed in terms of mass% based on oxide, SiO 2 : 58% to 66%, Al 2 O 3 : 15% to 22%, B 2 O 3 : 5% to 12%, MgO: 0% 6. The glass plate according to claim 5, comprising: 8%, CaO: 0% to 9%, SrO: 3% to 12.5%, BaO: 0% to 2%, and MgO + CaO + SrO + BaO: 9% to 18%. Manufacturing method.
  7.  前記無アルカリガラスは、酸化物基準の質量%表示で、SiO:54%~73%、Al:10.5%~22.5%、B:0%~5.5%、MgO:0%~8%、CaO:0%~9%、SrO:0%~16%、BaO:0%~2.5%、MgO+CaO+SrO+BaO:8%~26%である請求項5に記載のガラス板の製造方法。
     
    The alkali-free glass is expressed in terms of mass% 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%. 6. MgO: 0% to 8%, CaO: 0% to 9%, SrO: 0% to 16%, BaO: 0% to 2.5%, MgO + CaO + SrO + BaO: 8% to 26%. Manufacturing method of glass plate.
PCT/JP2013/053756 2012-03-27 2013-02-15 Method for producing glass plate WO2013145922A1 (en)

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