Classifications

• • 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
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/22—Surface treatment of glass, not in the form of fibres or filaments, by coating with other inorganic material
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B25/00—Annealing glass products
  • C03B25/04—Annealing glass products in a continuous way
  • C03B25/06—Annealing glass products in a continuous way with horizontal displacement of the glass products
  • C03B25/08—Annealing glass products in a continuous way with horizontal displacement of the glass products of glass sheets
• • 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
  • C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
• • 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
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
  • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
  • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container 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
• • 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
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
• • Y—GENERAL 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
  • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

• the present invention relates to a method for producing a plate glass made of non-alkali glass, which is suitable as a substrate glass for various displays and a substrate glass for a photomask.
• non alkali means that the content of alkali metal oxides (Li 2 O, Na 2 O, K 2 O) is 2000 mol ppm or less.
• the following characteristics have been required for various display substrate glasses, particularly those in which a metal or oxide thin film is formed on the surface.
• alkali metal oxide When an alkali metal oxide is contained, alkali metal ions diffuse into the thin film and deteriorate the film characteristics. Therefore, the content of the alkali metal oxide is extremely low. The oxide content is 2000 mol ppm or less.
• the strain point When exposed to a high temperature in the thin film forming process, the strain point is high so that the deformation (thermal shrinkage) associated with glass deformation and glass structural stabilization can be minimized.
• a-Si amorphous silicon
• p-Si polycrystalline silicon
• a glass having a small average thermal expansion coefficient is required to increase productivity and thermal shock resistance by increasing the temperature raising / lowering rate of the heat treatment for producing a liquid crystal display.
• BHF buffered hydrofluoric acid, mixed liquid of hydrofluoric acid and ammonium fluoride
• Patent Document 1 discloses SiO 2 —Al 2 O 3 —SrO glass that does not contain B 2 O 3 , but the temperature required for melting is high, which makes manufacturing difficult.
• Patent Document 2 discloses a SiO 2 —Al 2 O 3 —SrO crystallized glass that does not contain B 2 O 3 , but the temperature required for melting is high, resulting in difficulty in production.
• Patent Document 3 discloses a glass containing 0 to 3% by weight of B 2 O 3 , but the strain point of the examples is 690 ° C. or lower.
• Patent Document 4 discloses a glass containing 0 to 5 mol% of B 2 O 3 , but the average coefficient of thermal expansion at 50 to 300 ° C. exceeds 50 ⁇ 10 ⁇ 7 / ° C.
• Patent Document 5 discloses a glass containing 0 to 5 mol% of B 2 O 3 , but has a large thermal expansion and a high density.
• an alkali-free glass described in Patent Document 6 has been proposed.
• the alkali-free glass described in Patent Document 6 has a high strain point, can be molded by a float process, and is suitable for applications such as a display substrate and a photomask substrate.
• Japanese Laid-Open Patent Publication No. 62-1113735 Japanese Unexamined Patent Publication No. Sho 62-100450 Japanese Laid-Open Patent Publication No. 4-325435 Japanese Patent Laid-Open No. 5-232458 US Pat. No. 5,326,730 Japanese Patent Laid-Open No. 10-45422 Japanese republished patent 2009-148141
• the object of the present invention is to solve the above-mentioned drawbacks, to have a high strain point and to have a low viscosity, in particular, a low temperature T 4 at which the glass viscosity is 10 4 dPa ⁇ s, and further a protective layer for preventing wrinkles comprising a sulfate. It is providing the manufacturing method of the plate glass which consists of a non-alkali glass which can be efficiently formed in the glass ribbon after shape
• the present invention is a plate glass manufacturing method in which a glass raw material is melted to form molten glass, the molten glass is formed into a plate-like glass ribbon with a molding device, and then the glass ribbon is gradually cooled with a slow cooling device,
• the plate glass is made of the following alkali-free glass,
• T st the strain point of the alkali-free glass
• the time during which the atmosphere concentration immediately below the lower surface of the glass ribbon is 500 to 20000 ppm in the temperature range of T st + 70 ° C. to T st ⁇ 50 ° C.
• a plate glass manufacturing method for supplying SO 2 gas so as to be 30 seconds or longer is provided.
• the average coefficient of thermal expansion at 50 to 300 ° C. is 30 ⁇ 10 ⁇ 7 to 43 ⁇ 10 ⁇ 7 / ° C.
• the glass viscosity is 10 2 dPa ⁇ s.
• T 2 is 1710 ° C. or lower
• the temperature T 4 at which the glass viscosity is 10 4 dPa ⁇ s is 1320 ° C.
• MgO + CaO + SrO + BaO is 17-21,
• the present invention also relates to a method for producing plate glass, in which a glass raw material is melted to form molten glass, the molten glass is formed into a plate-like glass ribbon with a forming apparatus, and then the glass ribbon is gradually cooled with a slow cooling apparatus.
• the plate glass is made of the following alkali-free glass, When the strain point of the alkali-free glass is T st (° C.), the time during which the atmosphere concentration immediately below the lower surface of the glass ribbon is 500 to 20000 ppm in the temperature range of T st + 70 ° C. to T st ⁇ 50 ° C.
• a plate glass manufacturing method for supplying SO 2 gas so as to be 30 seconds or longer is provided.
• the average coefficient of thermal expansion at 50 to 300 ° C. is 30 ⁇ 10 ⁇ 7 to 43 ⁇ 10 ⁇ 7 / ° C.
• the glass viscosity is 10 2 dPa ⁇ s.
• T 2 is 1710 ° C. or lower
• the temperature T 4 at which the glass viscosity is 10 4 dPa ⁇ s is 1320 ° C.
• MgO + CaO + SrO + BaO is more than 18.2 and 21 or less
• MgO / (MgO + CaO + SrO + BaO) is 0.25 or more
• MgO / (MgO + CaO) is 0.3 or more
• MgO / (MgO + SrO) is 0.60 or more
• Al 2 O 3 ⁇ (MgO / (MgO + CaO + SrO + BaO) ) Is alkali-free glass of 5.5 or more.
• this invention provides the plate glass manufactured with the plate glass manufacturing method of this invention.
• the protective layer for preventing wrinkles of sulfate can be efficiently and uniformly formed on the glass ribbon, and the supply amount of sulfurous acid gas can be saved. As a result, a high-quality plate glass with less wrinkles can be obtained.
• the plate glass of the present invention is particularly suitable for a display substrate, a photomask substrate and the like for high strain point applications.
• the glass raw material prepared so that it might become the following glass composition 1 is used.
• the glass raw material prepared so that it might become the following glass composition 2 is used.
• MgO + CaO + SrO + BaO is more than 18.2 and 21 or less
• MgO / (MgO + CaO + SrO + BaO) is 0.25 or more
• MgO / (MgO + CaO) is 0.3 or more
• MgO / (MgO + SrO) is 0.60 or more
• Al 2 O 3 ⁇ (MgO / (MgO + CaO + SrO + BaO) ) Is alkali-free glass of 5.5 or more.
• the composition range of each component will be described. If the SiO 2 content is less than 66% (mol%, the same unless otherwise specified), the strain point is not sufficiently increased, the thermal expansion coefficient is increased, and the density is increased. Preferably it is 66.5% or more, more preferably 67% or more. If it exceeds 70%, the solubility decreases and the devitrification temperature increases. Preferably it is 69% or less.
• Al 2 O 3 suppresses the phase separation of the glass, lowers the thermal expansion coefficient and raises the strain point, but if it is less than 12%, this effect does not appear, and other components that increase the expansion increase. As a result, thermal expansion increases. Preferably it is 12.2% or more. If it exceeds 15%, the solubility of the glass may be deteriorated, or the devitrification temperature may be increased. Preferably it is 14.5% or less, More preferably, it is 14% or less, More preferably, it is 13.8% or less.
• B 2 O 3 can be added up to 1.5% in order to improve the melting reactivity of the glass and lower the devitrification temperature. However, if it is too much, the strain point is lowered. Also, the efficiency in forming a flaw preventing protection layer of sulfate when B 2 O 3 is too large in the glass ribbon is reduced. Therefore, it is preferably 1.3% or less, and more preferably 1% or less. Moreover, it is preferable not to contain substantially considering environmental load.
• MgO has the characteristics that it does not increase the expansion in alkaline earth and does not excessively lower the strain point, and also improves the solubility.
• the MgO content is more than 9.5% and not more than 13%. If it is 9.5% or less, the above-mentioned effect due to the addition of MgO is not sufficiently exhibited. However, if it exceeds 13%, the devitrification temperature may increase. 12.5% or less is preferable, 12% or less is more preferable, and 11.5% or less is more preferable.
• the MgO content is 5 to 9.5%. If it is less than 5%, the above-mentioned effect due to the addition of MgO is not sufficiently exhibited. 6% or more is preferable, and 7% or more is more preferable. However, if it exceeds 9.5%, the devitrification temperature may increase. 9.3% or less is preferable, and 9% or less is more preferable.
• CaO has the characteristics that it does not increase the expansion in alkaline earth after MgO, and does not excessively lower the strain point, and also improves the solubility.
• the CaO content is 4 to 9%. If it is less than 4%, the above-described effect due to the addition of CaO is not sufficiently exhibited. However, if it exceeds 9%, the devitrification temperature may increase, or a large amount of phosphorus, which is an impurity in limestone (CaCO 3 ) that is a CaO raw material, may be mixed. It is preferably 7% or less, more preferably 6% or less, and further preferably 5% or less.
• the CaO content is 4 to 11%.
• the devitrification temperature may increase, or a large amount of phosphorus, which is an impurity in limestone (CaCO 3 ) that is a CaO raw material, may be mixed. It is preferably 10% or less, more preferably 9% or less, further preferably 7% or less, and particularly preferably 6% or less.
• SrO improves the solubility without increasing the devitrification temperature of the glass, but if less than 0.5%, this effect does not appear sufficiently.
• Preferably it is 1.0% or more, More preferably, it is 2.0% or more. However, if it exceeds 4.5%, the expansion coefficient may increase. 4.0% or less is more preferable, and 3.5% or less is more preferable.
• BaO is not essential, but can be contained to improve solubility. However, if it is too much, the expansion and density of the glass are excessively increased, so the content is made 1% or less. Less than 1% is preferable, 0.5% or less is more preferable, and it is preferable not to contain substantially.
• ZrO 2 may be contained up to 2% in order to lower the glass melting temperature or to promote crystal precipitation during firing. If it exceeds 2%, the glass becomes unstable or the relative dielectric constant ⁇ of the glass increases. Preferably it is 1.5% or less, More preferably, it is 1.0% or less, More preferably, it is 0.5% or less, and it is especially preferable not to contain substantially.
• the solubility is poor, and the efficiency in forming a sulfate anti-fogging protective layer on the glass ribbon decreases. .
• it is 18% or more, More preferably, it is 18.5% or more.
• it exceeds 21% there is a risk that the thermal expansion coefficient cannot be reduced.
• the solubility is poor, and the efficiency when forming a protective layer for preventing sulfate wrinkles on the glass ribbon is reduced. To do. If it exceeds 21%, there is a risk that the thermal expansion coefficient cannot be reduced. Preferably it is 20% or less.
• MgO / (MgO + CaO + SrO + BaO) is 0.4 or more, preferably 0.45 or more.
• MgO / (MgO + CaO) is 0.4 or more, preferably 0.52 or more, more preferably 0.55 or more.
• MgO / (MgO + SrO) is 0.6 or more, preferably 0.7 or more.
• the total amount of MgO, CaO, SrO and BaO satisfies the above and satisfies the following three conditions, thereby increasing the strain point without increasing the devitrification temperature.
• the temperature T 4 at which the viscosity, particularly the glass viscosity, becomes 10 4 dPa ⁇ s can be lowered.
• MgO / (MgO + CaO + SrO + BaO) is 0.25 or more, preferably 0.3 or more, more preferably 0.4 or more, and further preferably 0.45 or more.
• MgO / (MgO + CaO) is 0.3 or more, preferably 0.4 or more, more preferably 0.52 or more, and further preferably 0.55 or more.
• MgO / (MgO + SrO) is 0.6 or more, preferably 0.7 or more.
• Al 2 O 3 ⁇ (MgO / (MgO + CaO + SrO + BaO) is preferably 5.5 or more because the Young's modulus can be increased. Preferably it is 5.75 or more, More preferably, it is 6.0 or more, More preferably, it is 6.25 or more, Most preferably, it is 6.5 or more.
• the efficiency at the time of forming the protective layer for wrinkle prevention in a glass ribbon improves by making a glass raw material contain 600 molppm or more of alkali metal oxides.
• the reason is as follows. Since alkali-free glass does not contain an alkali metal oxide, even if a high-temperature glass ribbon is exposed to the SO 2 gas atmosphere, a protective layer for preventing wrinkles due to precipitation of alkali metal sulfate cannot be formed.
• alkaline earth metal sulfates are precipitated instead of alkali metal sulfates.
• the present inventors added a small amount of alkali metal oxide to the glass raw material, thereby increasing the precipitation effect of alkaline earth metal sulfate and improving the efficiency when forming the protective layer for preventing wrinkles on the glass ribbon. I found out.
• the content of the alkali metal oxide when used as a substrate glass for various displays.
• the content of the metal oxide is 2000 mol ppm or less, such a problem will not occur. More preferably, it is 1500 mol ppm or less, More preferably, it is 1300 mol ppm or less, Most preferably, it is 1000 mol ppm or less.
• the glass raw material used in the present invention preferably contains an alkali metal oxide of 1500 mol ppm or less, more preferably 1300 mol ppm or less, more preferably 1000 mol ppm or less, and more preferably 700 to 900 mol ppm.
• Na 2 O and K 2 O are preferable from the viewpoint of the balance between the effect of improving the efficiency when forming the protective layer for preventing wrinkles on the glass ribbon and the raw material cost, and Na 2 O is more preferable.
• the glass raw material does not substantially contain P 2 O 5 . Furthermore, in order to facilitate recycling of the glass, it is preferable that the glass raw material does not substantially contain PbO, As 2 O 3 , or Sb 2 O 3 .
• ZnO, Fe 2 O 3 , SO 3 , F, Cl, SnO 2 can be added to the glass raw material in a total amount of 5% or less.
• the glass compositions 1 and 2 have relatively low solubility, it is preferable to use the following as raw materials for each component.
• Silica sand can be used as the silicon source of SiO 2 , but the proportion of particles having a median particle size D 50 of 20 ⁇ m to 27 ⁇ m, a particle size of 2 ⁇ m or less is 0.3% by volume or less, and the particle size is 100 ⁇ m or more.
• Using 2.5% by volume or less of silica sand can suppress the agglomeration of the silica sand and dissolve it, so that the silica sand can be easily dissolved, and there is less foam, and a plate glass with high homogeneity and flatness can be obtained. This is preferable.
• particle size in this specification is the equivalent sphere diameter of silica sand (meaning the primary particle size in the present invention), and specifically, in the particle size distribution of the powder measured by the laser diffraction / scattering method.
• particle size D 50 means that the volume frequency of particles larger than a certain particle size is 50% of the total powder in the particle size distribution of the powder measured by the laser diffraction method.
• the particle diameter occupied In other words, it refers to the particle diameter when the cumulative frequency is 50% in the particle size distribution of the powder measured by the laser diffraction method.
• ratio of particles having a particle diameter of 2 ⁇ m or less and “ratio of particles having a particle diameter of 100 ⁇ m or more” in this specification are measured by measuring the particle size distribution by a laser diffraction / scattering method, for example.
• the median particle diameter D 50 of silica sand is 25 ⁇ m or less, it is more preferable because dissolution of silica sand becomes easier. Further, the ratio of the particles having a particle diameter of 100 ⁇ m or more in the silica sand is particularly preferably 0% because the silica sand is more easily dissolved.
• Alkaline earth metal source An alkaline earth metal compound can be used as the alkaline earth metal source.
• Specific examples of the alkaline earth metal compound include carbonates such as MgCO 3 , CaCO 3 , BaCO 3 , SrCO 3 , (Mg, Ca) CO 3 (dolomite), MgO, CaO, BaO, SrO and the like.
• Oxides and hydroxides such as Mg (OH) 2 , Ca (OH) 2 , Ba (OH) 2 , and Sr (OH) 2 can be exemplified. It is preferable to contain a hydroxide of a similar metal since the undissolved amount of the SiO 2 component at the time of melting the glass raw material is reduced.
• the undissolved amount of the SiO 2 component contained in the silica sand increases, the undissolved SiO 2 is taken into the bubbles when the bubbles are generated in the molten glass and gathers near the surface layer of the molten glass. As a result, a difference in the composition ratio of SiO 2 occurs between the surface layer of the molten glass and the portion other than the surface layer, so that the homogeneity of the glass is lowered and the flatness is also lowered.
• the content of the alkaline earth metal hydroxide is preferably 15 to 100 mol% (MO conversion in terms of MO, where M is an alkaline earth metal element). Conversion), more preferably 30 to 100 mol% (MO conversion), and even more preferably 60 to 100 mol% (MO conversion), the undissolved amount of the SiO 2 component at the time of melting the glass raw material is reduced. Therefore, it is more preferable. As the molar ratio of the hydroxide in the alkaline earth metal source increases, the undissolved amount of the SiO 2 component at the time of melting the glass raw material decreases, so the higher the molar ratio of the hydroxide, the better.
• the alkaline earth metal source a mixture of an alkaline earth metal hydroxide and a carbonate, an alkaline earth metal hydroxide alone, or the like can be used.
• the carbonate it is preferable to use at least one of MgCO 3 , CaCO 3 and (Mg, Ca) (CO 3 ) 2 (dolomite).
• the alkaline earth metal hydroxide it is preferable to use at least one of Mg (OH) 2 and Ca (OH) 2 , and it is particularly preferable to use Mg (OH) 2 .
• the glass composition 1 contains B 2 O 3, as the boron source B 2 O 3, can be used boron compound.
• specific examples of the boron compound include orthoboric acid (H 3 BO 3 ), metaboric acid (HBO 2 ), tetraboric acid (H 2 B 4 O 7 ), and anhydrous boric acid (B 2 O 3 ). It is done. In the production of ordinary alkali-free glass, orthoboric acid is used because it is inexpensive and easily available.
• boric anhydride containing 10 to 100% by mass (in terms of B 2 O 3 ) out of 100% by mass of boron source (in terms of B 2 O 3 ).
• the boric anhydride is more preferably 20 to 100% by mass, and further preferably 40 to 100% by mass.
• orthoboric acid is preferable because it is inexpensive and easily available.
• Manufacture of plate glass is performed in the following procedure, for example.
• the raw materials of each component are prepared so as to become target components, which are continuously charged into a melting furnace, heated to 1500-1800 ° C. and melted.
• a plate glass can be obtained by forming this molten glass into a plate-like glass ribbon having a predetermined plate thickness using a molding apparatus, and then cooling the glass ribbon after slow cooling.
• sulfur dioxide (SO 2 ) gas is supplied to the glass ribbon so as to satisfy the following conditions in the slow cooling furnace.
• T st strain point of the alkali-free glass
• the SO 2 gas is supplied so as to achieve the above. If the atmospheric concentration is less than 500 ppm, the precipitation amount of alkaline earth metal sulfate may be reduced. More preferably, it is 1000 ppm or more. If the atmospheric concentration exceeds 20000 ppm, corrosion of the equipment may become a problem.
• the precipitation amount of an alkaline-earth metal sulfate may decrease. More preferably, it is 1 minute or more.
• the glass ribbon is preferably brought into contact with the SO 2 gas in an atmosphere having a water vapor dew point of 30 ° C. or higher. If the water vapor dew point is low, the precipitation effect of alkaline earth metal sulfate may not be improved. More preferably, it is 40 degreeC or more, More preferably, it is 50 degreeC or more.
• the glass of the present invention has a strain point of 710 ° C. or higher, and can suppress thermal shrinkage during panel production. Further, a solid phase crystallization method can be applied as a method for manufacturing a p-Si TFT. In the production method of the present invention, it is possible to supply the SO 2 gas at a higher temperature, it is formed efficiency flaw preventing protection layer consisting of alkaline earth metal sulfates.
• the strain point is more preferably 715 ° C or higher, and further preferably 720 ° C or higher. Especially preferably, it is 735 degreeC or more. When the strain point is 735 ° C.
• the strain point of the plate glass of the present invention is 750 ° C. or less.
• the glass of the present invention has a glass transition point of preferably 760 ° C. or higher, more preferably 770 ° C. or higher, and further preferably 780 ° C. or higher for the same reason as the strain point.
• the glass of the present invention has an average coefficient of thermal expansion at 50 to 300 ° C. of 30 ⁇ 10 ⁇ 7 to 43 ⁇ 10 ⁇ 7 / ° C., has high thermal shock resistance, and can increase productivity during panel manufacture.
• the average thermal expansion coefficient at 50 to 300 ° C. is preferably 35 ⁇ 10 ⁇ 7 to 40 ⁇ 10 ⁇ 7 / ° C.
• the specific gravity of the glass of the present invention is preferably 2.65 or less, more preferably 2.64 or less, and further preferably 2.62 or less.
• the temperature T 2 at which the viscosity ⁇ becomes 10 2 poise is 1710 ° C. or less, preferably less than 1710 ° C., more preferably 1700 ° C. or less, and further preferably 1690 ° C. or less. Therefore, dissolution is relatively easy.
• the glass of the present invention has a temperature T 4 at which the viscosity ⁇ becomes 10 4 poise is 1320 ° C. or less, preferably 1315 ° C. or less, more preferably 1310 ° C. or less, and further preferably 1305 ° C. or less, which is suitable for float molding. Yes.
• the glass of the present invention preferably has a devitrification temperature of 1350 ° C. or lower because molding by the float method is easy. Preferably it is 1340 degrees C or less, More preferably, it is 1330 degrees C or less.
• the devitrification temperature is obtained by putting crushed glass particles in a platinum dish and performing heat treatment for 17 hours in an electric furnace controlled at a constant temperature. It is an average value of the maximum temperature at which crystals are deposited inside and the minimum temperature at which crystals are not deposited.
• the glass of the present invention preferably has a Young's modulus of 84 GPa or more, more preferably 86 GPa or more, further 88 GPa or more, and further 90 GPa or more.
• the glass of the present invention preferably has a photoelastic constant of 31 nm / MPa / cm or less. Due to the birefringence of the glass substrate due to stress generated during the manufacturing process of the liquid crystal display panel and the liquid crystal display device, a phenomenon in which the black display becomes gray and the contrast of the liquid crystal display decreases may be observed. By setting the photoelastic constant to 31 nm / MPa / cm or less, this phenomenon can be suppressed small.
• the glass of the present invention preferably has a photoelastic constant of 25 nm / MPa / cm or less, considering the ease of securing other physical properties.
• the photoelastic constant can be measured by a disk compression method.
• the glass of the present invention preferably has a relative dielectric constant of 5.6 or more.
• the sensing sensitivity of the touch sensor is improved, the driving voltage is reduced, From the viewpoint of power saving, it is better that the glass substrate has a higher relative dielectric constant.
• the relative dielectric constant is 5.8 or more, More preferably, it is 6.0 or more, More preferably, it is 6.2 or more, Most preferably, it is 6.4 or more.
• the relative dielectric constant can be measured by the method described in JIS C-2141.
• Example 1 Comparative Examples 1 and 2
• the raw material of each component was prepared so that it might become the target composition shown in Table 1, it melt
• the content of the alkali metal oxide in the raw material used at this time the content of Na 2 O, the particle size of the silica sand in the used raw material, the median particle size D 50 , the proportion of particles having a particle size of 2 ⁇ m or less, and Table 1 shows the ratio of particles having a diameter of 100 ⁇ m or more.
• Table 1 also shows the molar ratio (in terms of MO) of the hydroxide raw material in the alkaline earth metal.
• the obtained glass was mirror-polished and then heat-treated in an SO 2 gas atmosphere at the heat treatment temperature, heat treatment time, SO 2 gas concentration and water vapor dew point shown in Table 2.
• the sulfate precipitation state on the surface of the obtained glass was measured as the surface S concentration (mass%) by fluorescent X-rays.
• Table 2 also shows the strain point and surface S concentration (% by mass) of the glass.
• the number of counts of S-k ⁇ rays is measured using a ⁇ 10 mm mask under the conditions shown in Table 3. After mirror-polishing glass with a known S concentration, the count number of S-k ⁇ rays was measured with a ⁇ 10 mm mask under the conditions shown in Table 3, and the S-k ⁇ ray count number and S concentration (mass%) Get correlation. By using the obtained correlation, the Sk ⁇ ray count number of the glass sample on which the sulfate salt is deposited is converted into the S concentration (mass%).
• the surface S concentration is preferably 0.15% by mass or more, and more preferably 0.2% by mass or more.
• Example 2 to 4 The raw materials of each component were prepared so as to have the target composition shown in Table 4, and were melted at a temperature of 1550 ° C. for 1 hour using a platinum crucible. After dissolution, it was poured out into a carbon plate, held at glass transition point + 30 ° C. for 1 hour, cooled at 1 ° C./min, and gradually cooled.
• the content of the alkali metal oxide in the raw material used at this time the content of Na 2 O, the particle size of the silica sand in the used raw material, the median particle size D 50 , the proportion of particles having a particle size of 2 ⁇ m or less, and Table 4 shows the ratio of particles having a diameter of 100 ⁇ m or more.
• Table 4 also shows the molar ratio (MO conversion) of the hydroxide raw material in the alkaline earth metal.
• the obtained glass was cut, and after mirror polishing, heat treatment was performed in an SO 2 gas atmosphere at the heat treatment temperature, heat treatment time, SO 2 gas concentration, and water vapor dew point shown in Table 5.
• the sulfate precipitation state on the surface of the obtained glass was measured as the surface S concentration (mass%) by fluorescent X-rays.
• Table 5 also shows the strain point and surface S concentration (mass%) of the glass.
• the plate glass obtained by the present invention has a high strain point and is suitable for uses such as a display substrate and a photomask substrate. Moreover, it is suitable also for uses, such as a board

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