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
  • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
  • C03C21/001—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions
  • C03C21/002—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions to perform ion-exchange between alkali ions
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B17/00—Forming molten glass by flowing-out, pushing-out, extruding or drawing downwardly or laterally from forming slits or by overflowing over lips
  • C03B17/06—Forming glass sheets
  • C03B17/064—Forming glass sheets by the overflow downdraw fusion process; Isopipes therefor
• • 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
  • C03B25/10—Annealing glass products in a continuous way with vertical displacement of the glass products
  • C03B25/12—Annealing glass products in a continuous way with vertical 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
  • 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
• • 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
• • 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
  • C03C4/00—Compositions for glass with special properties
  • C03C4/18—Compositions for glass with special properties for ion-sensitive glass
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
  • H01L31/042—PV modules or arrays of single PV cells
  • H01L31/048—Encapsulation of modules
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
  • H01L31/042—PV modules or arrays of single PV cells
  • H01L31/048—Encapsulation of modules
  • H01L31/0488—Double glass encapsulation, e.g. photovoltaic cells arranged between front and rear glass sheets
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K5/00—Casings, cabinets or drawers for electric apparatus
  • H05K5/02—Details
• • 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
  • C03C2204/00—Glasses, glazes or enamels with special properties
• • 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
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31—Surface property or characteristic of web, sheet or block
  • Y10T428/315—Surface modified glass [e.g., tempered, strengthened, etc.]

Definitions

• the present invention relates to a tempered glass and a tempered glass sheet, and a glass to be tempered, and more particularly, to a tempered glass and a tempered glass sheet, and a glass to be tempered suitable for a cover glass for a cellular phone, a digital camera, a personal digital assistant (PDA), or a solar battery, or a glass substrate for a display, in particular, a touch panel display.
• a tempered glass and a tempered glass sheet and a glass to be tempered
• a glass to be tempered suitable for a cover glass for a cellular phone, a digital camera, a personal digital assistant (PDA), or a solar battery, or a glass substrate for a display, in particular, a touch panel display.
• PDA personal digital assistant
• Devices such as a cellular phone, a digital camera, a PDA, a touch panel display, a large-screen television, and contact-less power transfer show a tendency of further prevalence.
• a tempered glass which is produced by applying tempering treatment to glass through ion exchange treatment or the like, is used for those applications (see Patent Literature 1 and Non Patent Literature 1).
• the tempered glass has been more and more frequently used in exterior parts of, for example, digital signage, mice, and smartphones.
• Characteristics required of the tempered glass include (1) high mechanical strength, (2) low cost, and (3) high dimensional accuracy.
• a structure in which a plurality of panels are linked together has been adopted in an increasing number of cases, and in association with this, a higher level of dimensional accuracy has been demanded.
• a conventional dimensional tolerance has been about ⁇ 4,000 ppm
• a demand has arisen for a dimensional tolerance of about ⁇ 1,000 ppm.
• a tempered glass (glass to be tempered) is liable to undergo a dimensional change between before and after tempering treatment. Thus, it is not easy to increase the dimensional accuracy of the tempered glass.
• the tempering treatment is generally performed by immersing the glass to be tempered in a high-temperature (for example, from 300 to 500° C.) KNO 3 molten salt.
• a high-temperature for example, from 300 to 500° C.
• KNO 3 molten salt for example, from 300 to 500° C.
• the tempering treatment of a large-size glass sheet to be tempered involves a problem in that the glass is liable to undergo breakage owing to a thermal shock when the glass to be tempered is immersed or when the tempered glass sheet is taken out.
• such method requires a long period of time, and hence involves a risk that the manufacturing cost of the tempered glass sheet may soar.
• the present invention has been made in view of the above-mentioned circumstances, and a technical object of the present invention is to devise a tempered glass, tempered glass sheet, and glass to be tempered that have high ion exchange performance, hardly undergo a dimensional change before and after tempering treatment, and have high thermal shock resistance.
• a tempered glass of the present invention has a compressive stress layer in a surface thereof, comprises as a glass composition, in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 2% of Li 2 O, and 5 to 25% of Na 2 O, and is substantially free of As 2 O 3 , Sb 2 O 3 , PbO, and F.
• the gist of the phrase “substantially free of As 2 O 3 ” resides in that As 2 O 3 is not added positively as a glass component, but contamination with As 2 O 3 as an impurity is allowable. Specifically, the phrase means that the content of As 2 O 3 is less than 0.1 mass %.
• the gist of the phrase “substantially free of Sb 2 O 3 ” resides in that Sb 2 O 3 is not added positively as a glass component, but contamination with Sb 2 O 3 as an impurity is allowable. Specifically, the phrase means that the content of Sb 2 O 3 is less than 0.1 mass %.
• the gist of the phrase “substantially free of PbO” resides in that PbO is not added positively as a glass component, but contamination with PbO as an impurity is allowable. Specifically, the phrase means that the content of PbO is less than 0.1 mass %.
• the gist of the phrase “substantially free of F” resides in that F is not added positively as a glass component, but contamination withF as an impurity is allowable. Specifically, the phrase means that the content of F is less than 0.1 mass %.
• the introduction of given amounts of Al 2 O 3 and the alkali metal oxides into the glass composition can enhance ion exchange performance, thermal shock resistance, and devitrification resistance. Further, the devitrification resistance can be enhanced by regulating the contents and content ratios of Al 2 O 3 , B 2 O 3 , and alkaline earth metal oxides.
• the tempered glass of the present invention preferably comprises as a glass composition, in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 1.7% of Li 2 O, more than 7.0 to 25% of Na 2 O, and 0 to 2% of SrO.
• the tempered glass of the present invention preferably comprises as a glass composition, in terms of mass %, 50 to 76% of SiO 2 , more than 16.0 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 1.7% of Li 2 O, more than 7.0 to 25% of Na 2 O, 0 to 2% of SrO, and 0 to 4.5% of TiO 2 .
• the tempered glass of the present invention preferably comprises as a glass composition, in terms of mass %, 50 to 76% of SiO 2 , more than 16.0 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 1.7% of Li 2 O, more than 7.0 to 25% of Na 2 O, 0 to 2% of SrO, 0 to 0.5% of TiO 2 , and 0 to 4% of ZrO 2 .
• the tempered glass of the present invention preferably comprises as a glass composition, in terms of mass %, 50 to 76% of SiO 2 , more than 16.0 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 1.7% of Li 2 O, more than 7.0 to 25% of Na 2 O, 0 to 2% of SrO, 0 to 0.5% of TiO 2 , 0 to 4% of ZrO 2 , and 0 to 1% of P 2 O 5 , and preferably has a molar ratio (MgO+CaO+SrO+BaO)/(Al 2 O 3 +B 2 O 3 ) of from 0 to 0.60.
• mass % 50 to 76% of SiO 2 , more than 16.0 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 1.7% of Li 2 O, more than 7.0 to 25% of Na 2 O, 0 to 2% of SrO, 0 to 0.5% of TiO
• MgO+CaO+SrO+BaO refers to the total amount of MgO, CaO, SrO, and BaO.
• Al 2 O 3 +B 2 O 3 refers to the total amount of Al 2 O 3 and B 2 O 3 .
• the tempered glass of the present invention preferably comprises as a glass composition, in terms of mass %, 50 to 76% of SiO 2 , more than 16.0 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to less than 1.0% of Li 2 O, more than 7.0 to 25% of Na 2 O, 0 to 2% of SrO, 0 to 0.5% of TiO 2 , 0 to 2% of ZrO 2 , 0.2 to 3% of SnO 2 , and to 1% of P 2 O 5 , and preferably has a molar ratio (MgO+CaO+SrO+BaO)/(Al 2 O 3 +B 2 O 3 ) of from 0 to 0.55.
• mass % 50 to 76% of SiO 2 , more than 16.0 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to less than 1.0% of Li 2 O, more than 7.0 to 25% of Na 2 O, 0 to
• the tempered glass of the present invention preferably comprises as a glass composition, in terms of mass %, 50 to 73% of SiO 2 , more than 16.0 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to less than 1.0% of Li 2 O, more than 7.0 to 25% of Na 2 O, 10 to 30% of Li 2 O+Na 2 O+K 2 O, 0 to 4% of CaO, 0 to 2% of SrO, 0 to 0.5% of TiO 2 , 0 to 2% of ZrO 2 , 0.2 to 3% of SnO 2 , and 0 to 1% of P 2 O 5 , and preferably has a molar ratio (MgO+CaO+SrO+BaO)/(Al 2 O 3 +B 2 O 3 ) of from 0 to 0.55.
• the term “Li 2 O+Na 2 O+K 2 O” means the total amount of Li 2 O, Na 2 O, and K 2 O
• a compression stress value of the compression stress layer be 300 MPa or more and 1,200 MPa or less, and a thickness of the compression stress layer be 10 ⁇ m or more and 60 ⁇ m or less.
• compression stress value of the compression stress layer and the “thickness of the compression stress layer” refer to values calculated from the number of interference fringes and intervals therebetween, the interference fringes being observed when a sample is observed using a surface stress meter (for example, FSM-6000 manufactured by TOSHIBA CORPORATION).
• the tempered glass of the present invention preferably has a liquidus temperature of 1,200° C. or less.
• liquidus temperature refers to a temperature at which crystals of glass are deposited after glass powder that passes through a standard 30-mesh sieve (sieve opening: 500 ⁇ m) and remains on a 50-mesh sieve (sieve opening: 300 ⁇ m) is placed in a platinum boat and then kept for 24 hours in a gradient heating furnace.
• the tempered glass of the present invention preferably has a liquidus viscosity of 10 4.0 dPa ⁇ s or more.
• liquidus viscosity refers to a value obtained through measurement of a viscosity of glass at the liquidus temperature by a platinum sphere pull up method.
• the tempered glass of the present invention preferably has a temperature at 10 4.0 dPa ⁇ s of 1,300° C. or less.
• the phrase “temperature at 10 4.0 dPa ⁇ s” refers to a value obtained through measurement by a platinum sphere pull up method.
• the tempered glass of the present invention preferably has a thermal expansion coefficient in a temperature range of from 25 to 380° C. of 100 ⁇ 10 ⁇ 7 /° C. or less.
• the phrase “thermal expansion coefficient in a temperature range of from 25 to 380° C.” refers to a value obtained by measuring an average thermal expansion coefficient with a dilatometer.
• a tempered glass sheet of the present invention comprises the tempered glass.
• a tempered glass sheet of the present invention is a tempered glass sheet having a length dimension of 500 mm or more, a width dimension of 300 mm or more, and a thickness of from 0.5 to 2.0 mm, having a compression stress value of a compression stress layer of 300 MPa or more and 1,200 MPa or less and a thickness of the compression stress layer of 10 ⁇ m or more and 60 ⁇ m or less, and being subjected to tempering treatment so as to have a dimensional change rate S between before and after tempering treatment of from ⁇ 1,000 ppm to +1,000 ppm.
• the “dimensional change rate S between before and after tempering treatment” refers to a value obtained by measuring a length dimension Lb before tempering treatment and a length dimension La after tempering treatment, and then performing calculation by substituting the length dimensions into the following equation:
• the tempered glass sheet of the present invention preferably has a Young's modulus of 65 GPa or more.
• the tempered glass sheet of the present invention preferably has a fictive temperature Tf of 500° C. or more.
• the “fictive temperature Tf” is an indicator for the molecular structure of glass reflecting thermal history during the cooling and solidification of a glass melt. Its value increases as the cooling is performed more rapidly, and lowers as the cooling is performed more slowly.
• a measurement method for the fictive temperature If is described below. A sample is kept at a temperature equal to or higher than its strain point for a sufficient period of time (for example, 24 hours), then rapidly cooled by, for example, being immediately brought into contact with a metal sheet, and measured for its dimensional change.
• the dimensional change shows a positive value ⁇ L1
• the dimensional change shows a negative value ⁇ L2.
• T1-T2 is from 0 to 20° C.
• Tf ( T 2 ⁇ L 1 ⁇ T 1 ⁇ L 2)/( ⁇ L 1 ⁇ L 2)
• the tempered glass sheet of the present invention is preferably formed by an overflow down-draw method.
• the “overflow down-draw method” refers to a method comprising causing a molten glass to overflow from both sides of a heat-resistant forming trough, and subjecting the overflowing molten glasses to down-draw downward while the molten glasses are joined at the lower end of the forming trough, to thereby manufacture a glass sheet.
• surfaces that are to serve as the surfaces of the glass sheet are formed in a state of free surfaces without being brought into contact with the surface of the forming trough. Accordingly, a glass sheet having satisfactory surface quality in an unpolished state can be manufactured at low cost.
• the tempered glass sheet of the present invention is preferably cut at a position spaced apart downwardly by 1,000 mm or more from a lower end of a forming trough used in the overflow down-draw method.
• the tempered glass sheet of the present invention is preferably used for a touch panel display.
• the tempered glass sheet of the present invention is preferably used for a cover glass for a cellular phone.
• the tempered glass sheet of the present invention is preferably used for a cover glass for a solar battery.
• the tempered glass sheet of the present invention is preferably used for a protective member for a display.
• a tempered glass sheet of the present invention is a tempered glass sheet having a length dimension of 500 mm or more, a width dimension of 300 mm or more, and a thickness of from 0.3 to 2.0 mm, comprising as a glass composition, in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 2% of Li 2 O, 5 to 25% of Na 2 O, 10 to 30% of Li 2 O+Na 2 O+K 2 O, 0 to 2% of SrO, 0 to less than 0.50% of TiO 2 , 0 to 4% of ZrO 2 , 0.2 to 3% of SnO 2 , and 0 to 1% of P 2 O 5 , having a molar ratio (MgO+CaO+SrO+BaO)/(Al 2 O 3 +B 2 O 3 ) of from 0 to 0.60, being substantially free of As 2 O 3
• a glass to be tempered of the present invention comprises as a glass composition, in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 2% of Li 2 O, and 5 to 25% of Na 2 O, and being substantially free of As 2 O 3 , Sb 2 O 3 , PbO, and F.
• a glass to be tempered of the present invention has a dimensional change rate S between before and after tempering treatment (immersion in a KNO 3 molten salt at 440° C. for 6 hours) of from ⁇ 1,000 ppm to +1,000 ppm. It should be noted that as the KNO 3 molten salt, there is used one having no history of being used.
• the glass to be tempered of the present invention preferably has a fictive temperature Tf of 500° C. or more.
• the tempered glass of the present invention has high ion exchange performance. Accordingly, even when ion exchange treatment is performed for a short period of time, the compression stress value of its compression stress layer increases and the compression stress layer is formed so as to reach a deep portion. As a result, its mechanical strength is enhanced, and a variation in mechanical strength reduces.
• the tempered glass of the present invention is excellent in denitrification resistance, and hence can be efficiently formed into a shape by the overflow down-draw method. It should be noted that according to the overflow down-draw method, a glass sheet having a large size and a small thickness can be formed in a large amount.
• the tempered glass of the present invention has a low thermal expansion coefficient, and hence the time required for preheating before tempering treatment and/or the time required for annealing after tempering treatment can be shortened.
• the tempered glass of the present invention has a high Young's modulus and a high fictive temperature Tf, and hence the dimensional change between before and after tempering treatment can be reduced.
• a tempered glass of the present invention has a compression stress layer in a surface thereof.
• a method of forming the compression stress layer in the surface includes a physical tempering method and a chemical tempering method.
• the tempered glass of the present invention is preferably produced by the chemical tempering method.
• the chemical tempering method is a method involving introducing alkali ions each having a large ion radius into the surface of glass by ion exchange treatment at a temperature equal to or lower than a strain point of the glass.
• the chemical tempering method is used to form a compression stress layer, the compression stress layer can be properly formed even in the case where the thickness of the glass is small.
• the tempered glass does not easily break unlike a tempered glass produced by applying a physical tempering method such as an air cooling tempering method.
• SiO 2 is a component that forms a network of glass, and the content of SiO 2 is from 50 to 80%, preferably from 55 to 76%, more preferably from 55 to 75%, more preferably from 55 to 73%, more preferably from 55 to 72%, more preferably from 56 to 69%, particularly preferably from 57 to 67%.
• the content of SiO 2 is too small in glass, vitrification does not occur easily, the thermal expansion coefficient becomes too high, and the thermal shock resistance easily lowers.
• the content of SiO 2 is too large in glass, the meltability and formability easily lower, and the thermal expansion coefficient becomes too low, with the result that it becomes difficult to match the thermal expansion coefficient with those of peripheral materials.
• Al 2 O 3 is a component that enhances the ion exchange performance of glass and a component that enhances the strain point or Young's modulus, and the content of Al 2 O 3 is from 10 to 30%. When the content of Al 2 O 3 is too small in glass, the ion exchange performance may not be exhibited sufficiently.
• the lower limit range of Al 2 O 3 is preferably 12% or more, more preferably 13% or more, more preferably 14% or more, more preferably 15% or more, more preferably 15.5% or more, more preferably more than 16.0%, more preferably 16.1% or more, more preferably 16.3% or more, more preferably 16.5% or more, more preferably 17.1% or more, more preferably 17.5% or more, more preferably 18% or more, particularly preferably 18.5% or more.
• the upper limit range of the content of Al 2 O 3 is preferably 28% or less, more preferably 26% or less, more preferably 24% or less, more preferably 23.5% or less, more preferably 22% or less, more preferably 21% or less, more preferably 20% or less, particularly preferably 19% or less. It should be noted that in the case where high importance is placed on mechanical strength, for example, in the case where tempering treatment is performed after cutting into a cover glass shape and polishing, it is preferred to increase the content of Al 2 O 3 to the extent possible by sacrificing acid resistance to some degree.
• the lower limit range of the content of Al 2 O 3 is preferably 16% or more, more preferably 17% or more, more preferably 18% or more, more preferably 18.5% or more, more preferably 19% or more, more preferably 20% or more, more preferably 21% or more, more preferably 22% or more, particularly preferably 23% or more.
• the upper limit range of the content of Al 2 O 3 is preferably 30% or less, more preferably 29% or less, more preferably 27% or less, more preferably 26% or less, more preferably 25.5% or less, particularly preferably 25% or less.
• B 2 O 3 is a component that lowers the viscosity at high temperature and density of glass, stabilizes the glass for a crystal to be unlikely precipitated, and lowers the liquidus temperature of the glass.
• the lower limit range of the content of B 2 O 3 is preferably 0% or more, more preferably 0.01% or more, more preferably 0.05% or more, more preferably 0.1% or more, particularly preferably 0.4% or more.
• coloring on the surface of glass called weathering may occur, water resistance may lower, and the thickness of a compression stress layer is liable to decrease.
• the upper limit range of the content of B 2 O 3 is preferably 6% or less, more preferably 5% or less, more preferably 4% or less, more preferably 3.95% or less, more preferably 3% or less, more preferably 2% or less, particularly preferably less than 2.0%.
• Li 2 O is an ion exchange component and is a component that lowers the viscosity at high temperature of glass to increase the meltability and the formability, and increases the Young's modulus. Further, Li 2 O has a great effect of increasing the compression stress value of glass among alkali metal oxides, but when the content of Li 2 O becomes extremely large in a glass system containing Na 2 O at 7% or more, the compression stress value tends to lower contrarily. Further, when the content of Li 2 O is too large in glass, the liquidus viscosity lowers, easily resulting in the denitrification of the glass, and the thermal expansion coefficient becomes too high, with the result that the thermal shock resistance lowers and it becomes difficult to match the thermal expansion coefficient with those of peripheral materials.
• the upper limit range of the content of Li 2 O is from 0 to 2%, and is preferably from 0 to 1.7%, more preferably from 0 to 1.5%, more preferably from 0 to 1%, more preferably from 0 to less than 1.0%, more preferably from 0 to 0.5%, more preferably from 0 to 0.3%, more preferably from 0 to 0.1%, particularly preferably from 0 to 0.05%.
• Na 2 O is an ion exchange component and is a component that lowers the viscosity at high temperature of glass to increase the meltability and formability. Na 2 O is also a component that improves the devitrification resistance of glass. When the content of Na 2 O is too small in glass, the meltability lowers, the thermal expansion coefficient lowers, and the ion exchange performance is liable to lower.
• the content of Na 2 O is 5% or more
• the lower limit range of the content of Na 2 O is 7% or more, preferably more than 7.0%, more preferably 8% or more, more preferably 9% or more, more preferably 10% or more, more preferably 11% or more, more preferably 12% or more, more preferably 13% or more, more preferably 13.8% or more, particularly preferably 14% or more.
• the thermal expansion coefficient becomes too high, with the result that the thermal shock resistance lowers, and it becomes difficult to match the thermal expansion coefficient with those of peripheral materials.
• the strain point lowers excessively, and the glass composition loses its component balance, with the result that the devitrification resistance lowers contrarily in some cases.
• the content of Na 2 O is 25% or less
• the upper limit range of the content of Na 2 O is preferably 23% or less, more preferably 21% or less, more preferably 19% or less, more preferably 17% or less, more preferably 16.3% or less, more preferably 16% or less, particularly preferably 15% or less.
• K 2 O is a component that promotes ion exchange and is a component that allows the thickness of a compression stress layer to be easily enlarged among alkali metal oxides.
• K 2 O is also a component that lowers the viscosity at high temperature of glass to increase the meltability and formability.
• K 2 O is also a component that improves devitrification resistance.
• the thermal expansion coefficient of glass becomes too large, the thermal shock resistance of the glass lowers, and it becomes difficult to match the thermal expansion coefficient with those of peripheral materials. Further, the strain point lowers excessively, and the glass composition loses its component balance, with the result that the devitrification resistance tends to lower contrarily.
• the upper limit range of the content of K 2 O is preferably 10% or less, more preferably 9% or less, more preferably 8% or less, more preferably 7% or less, particularly preferably 6% or less. It should be noted that when K 2 O is added, the addition amount is preferably 0.1% or more, more preferably 0.5% or more, more preferably 1% or more, more preferably 1.5% or more, particularly preferably 2% or more. In addition, when the addition of K 2 O is avoided as much as possible, the content of K 2 O is preferably from 0 to 1%, more preferably from 0 to less than 1.0%, particularly preferably from 0 to 0.05%.
• the lower limit range of the content of Li 2 O+Na 2 O+K 2 O is preferably 10% or more, more preferably 11% or more, more preferably 12% or more, more preferably 13% or more, more preferably 14% or more, more preferably 14.5% or more, more preferably 15% or more, more preferably 15.5% or more, particularly preferably 16% or more.
• the thermal expansion coefficient becomes too high, with the result that the thermal shock resistance lowers and it becomes difficult to match the thermal expansion coefficient with those of peripheral materials.
• the upper limit range of the content of Li 2 O+Na 2 O+K 2 O is preferably 30% or less, more preferably 27% or less, particularly preferably 25% or less.
• MgO is a component that reduces the viscosity at high temperature of glass to enhance the meltability and formability, and increases the strain point and Young's modulus, and is a component that has a great effect of enhancing the ion exchange performance among alkaline earth metal oxides.
• the content of MgO is preferably from 0 to 10%.
• the lower limit range of the content of MgO is preferably 0% or more, more preferably 0.5% or more, more preferably 1% or more, more preferably 1.2% or more, more preferably 1.3% or more, particularly preferably 1.4% or more.
• the content of MgO is too large in glass, the density and thermal expansion coefficient easily increase, and the devitrification of the glass tends to occur easily.
• the upper limit range of the content of MgO is preferably 9% or less, more preferably 8% or less, more preferably 7% or less, more preferably 6% or less, more preferably 5% or less, more preferably 4% or less, more preferably 3.5% or less, more preferably 3% or less, more preferably 2.5% or less, more preferably 2.4% or less, more preferably 2.3% or less, particularly preferably 2.2% or less.
• the mass ratio B 2 O 3 /MgO is preferably from 0.01 to 5, more preferably from 0.01 to 3.5, more preferably from 0.01 to 2.2, particularly preferably from 0.01 to 1.5. With this, the viscosity at high temperature and the devitrification resistance can be easily made proper.
• the lower limit value of the molar ratio (3MgO+Al 2 O 3 )/Na 2 O is preferably 0.0 or more, more preferably 0.5 or more, more preferably 0.6 or more, more preferably 0.7 or more, more preferably 0.8 or more, more preferably 0.9 or more, particularly preferably 1.0 or more.
• the upper limit value of the molar ratio (3MgO+Al 2 O 3 )/Na 2 O is preferably 2.5 or less, more preferably 2.0 or less, more preferably 1.9 or less, more preferably 1.8 or less, more preferably 1.7 or less, more preferably 1.6 or less, more preferably 1.5 or less, particularly preferably 1.4 or less.
• CaO has greater effects of reducing the viscosity at high temperature of glass to enhance the meltability and formability and increasing the strain point and Young's modulus without involving a reduction in denitrification resistance as compared to other components.
• the content of CaO is too large in glass, the density and thermal expansion coefficient increase, and the glass composition loses its component balance, with the result that the glass is liable to denitrify contrarily, the ion exchange performance lowers, and the deterioration of an ion exchange solution tends to occur easily.
• the content of CaO is preferably from 0 to 6%, more preferably from 0 to 5%, more preferably from 0 to 4%, more preferably from 0 to 3.5%, more preferably from 0 to 3%, more preferably from 0 to 2%, more preferably from 0 to 1%, more preferably from 0 to 0.5%, particularly preferably from 0 to 0.1%.
• SrO is a component that reduces the viscosity at high temperature of glass to enhance the meltability and formability, and increases the strain point and Young's modulus.
• the content of SrO is preferably from 0 to 2%, more preferably from 0 to 1.5%, more preferably from 0 to 1%, more preferably from 0 to 0.5%, more preferably from 0 to 0.1%, particularly preferably from 0 to less than 0.1%.
• BaO is a component that reduces the viscosity at high temperature of glass to enhance the meltability and formability, and increases the strain point and Young's modulus.
• the content of BaO is preferably from 0 to 6%, more preferably from 0 to 3%, more preferably from 0 to 1.5%, more preferably from 0 to 1%, more preferably from 0 to 0.5%, more preferably from 0 to 0.1%, particularly preferably from 0 to less than 0.1%.
• the content of MgO+CaO+SrO+BaO is preferably from 0 to 9.9%, more preferably from 0 to 8%, more preferably from 0 to 6%, particularly preferably from 0 to 5%.
• the upper limit range of the molar ratio (MgO+CaO+SrO+BaO)/(Al 2 O 3 +B 2 O 3 ) is preferably 1 or less, more preferably 0.9 or less, more preferably 0.8 or less, more preferably 0.75 or less, more preferably 0.70 or less, more preferably 0.65 or less, more preferably 0.60 or less, particularly preferably 0.55 or less.
• the lower limit range of the molar ratio (MgO+CaO+SrO+BaO)/(Al 2 O 3 +B 2 O 3 ) is preferably 0 or more, more preferably 0.05 or more, more preferably 0.10 or more, particularly preferably 0.12 or more.
• TiO 2 is a component that enhances the ion exchange performance of glass and is a component that reduces the viscosity at high temperature.
• the content of TiO 2 is preferably from 0 to 4.5%, more preferably from 0 to 0.5%, particularly preferably from 0 to 0.3%.
• ZrO 2 is a component that remarkably enhances the ion exchange performance of glass, and is a component that increases the viscosity of glass around the liquidus viscosity and the strain point.
• the content of ZrO 2 is preferably from 0 to 5%, more preferably from 0 to 4%, more preferably from 0 to 3%, particularly preferably from 0.001 to 2%.
• ZnO is a component that enhances the ion exchange performance of glass and is a component that has a great effect of increasing the compression stress value, in particular. Further, ZnO is a component that reduces the viscosity at high temperature of glass without reducing the viscosity at low temperature. However, when the content of ZnO is too large in glass, there is a tendency that the glass undergoes phase separation, the denitrification resistance lowers, the density increases, and the thickness of the compression stress layer decreases. Thus, the content of ZnO is preferably from 0 to 6%, more preferably from 0 to 5%, more preferably from 0 to 3%, particularly preferably from 0 to 1%.
• P 2 O 5 is a component that enhances the ion exchange performance of glass and is a component that increases the thickness of the compression stress layer, in particular.
• the content of P 2 O 5 is preferably from 0 to 10%, more preferably from 0 to 3%, more preferably from 0 to 1%, particularly preferably from 0 to 0.5%.
• one kind or two or more kinds selected from the group consisting of Cl, SO 3 , and CeO 2 may be added at from 0 to 3%.
• SnO 2 has an effect of enhancing ion exchange performance.
• the content of SnO 2 is preferably from 0 to 3%, more preferably from 0.01 to 3%, more preferably from 0.05 to 3%, more preferably from 0.1 to 3%, particularly preferably from 0.2 to 3%.
• the content of SnO 2 +SO 3 +Cl is preferably from 0.01 to 3%, more preferably from 0.05 to 3%, more preferably from 0.1 to 3%, particularly preferably from 0.2 to 3% from the viewpoint of simultaneously achieving a fining effect and an effect of enhancing ion exchange performance. It should be noted that the term “SnO 2 +SO 3 +Cl” refers to the total amount of SnO 2 , Cl, and SO 3 .
• the content of Fe 2 O 3 is preferably less than 1,000 ppm (less than 0.1%), more preferably less than 800 ppm, more preferably less than 600 ppm, more preferably less than 400 ppm, particularly preferably less than 300 ppm. Further, the molar ratio Fe 2 O 3 /(Fe 2 O 3 +SnO 2 ) is controlled to preferably 0.8 or more, more preferably 0.9 or more, particularly preferably 0.95 or more, while the content of Fe 2 O 3 is controlled in the above-mentioned range. With this, the transmittance (400 to 770 nm) of glass having a thickness of 1 mm is likely to improve (by, for example, 90% or more).
• a rare earth oxide such as Nd 2 O 3 or La 2 O 3 is a component that enhances the Young's modulus.
• the cost of the raw material itself is high, and when the rare earth oxide is added in a large amount, the denitrification resistance is liable to deteriorate.
• the content of the rare earth oxide is preferably 3% or less, more preferably 2% or less, more preferably 1% or less, more preferably 0.5% or less, particularly preferably 0.1% or less.
• the tempered glass of the present invention is substantially free of As 2 O 3 , Sb 2 O 3 , PbO, and F as a glass composition from the standpoint of environmental considerations.
• the tempered glass is preferably substantially free of Bi 2 O 3 from the standpoint of environmental considerations.
• the gist of the phrase “substantially free of Bi 2 O 3 ” resides in that Bi 2 O 3 is not added positively as a glass component, but contamination with Bi 2 O 3 as an impurity is allowable. Specifically, the phrase means that the content of Bi 2 O 3 is less than 0.05%.
• a molar ratio B 2 O 3 /Al 2 O 3 is preferably regulated within the range of from 0.0 to 0.2, in particular from 0.0 to 0.1, and a molar ratio Na 2 O/Al 2 O 3 is preferably regulated within the range of from 0.8 to 1.2, in particular, from 0.9 to 1.1.
• the “crack generation rate” refers to a value measured as described below.
• a Vickers indenter set to a predetermined load is driven into a glass surface (optically polished surface) for 15 seconds, and 15 seconds after that, the number of cracks generated from the four corners of the indentation is counted (4 per indentation at maximum).
• the indenter is driven in this manner 20 times, the total number of generated cracks is determined, and then the crack generation rate is determined by the following expression: total number of generated cracks/80 ⁇ 100.
• the content of Na 2 O is preferably regulated within the range of from 13.8 to 16.3, and more than 16.0 to 25% of Al 2 O 3
• the content of B 2 O 3 is preferably regulated within the range of from 0.01 to 3.95%.
• the suitable content range of each component can be appropriately selected to attain a suitable glass composition range. Of those, particularly suitable glass composition ranges are as follows:
• (1) comprising as a glass composition, in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 2% of Li 2 O, and 5 to 25% of Na 2 O, and being substantially free of As 2 O 3 , Sb 2 O 3 , PbO, and F;
• (2) comprising as a glass composition, in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 1.7% of Li 2 O, 5 to 25% of Na 2 O, and 0 to 2% of SrO, and being substantially free of As 2 O 3 , Sb 2 O 3 , PbO, and F;
• (3) comprising as a glass composition, in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 1.7% of Li 2
• the tempered glass of the present invention preferably has the following characteristics, for example.
• the tempered glass of the present invention has a compression stress layer in a surface thereof.
• the compression stress value of the compression stress layer is preferably 300 MPa or more, more preferably 400 MPa or more, more preferably 500 MPa or more, more preferably 600 MPa or more, particularly preferably 900 MPa or more.
• the compression stress value of the compression stress layer is preferably 1,200 MPa or less.
• the compression stress value is increased by increasing the content of Al 2 O 3 , TiO 2 , ZrO 2 , MgO, or ZnO in the glass composition or by decreasing the content of SrO or BaO in the glass composition. Further, there is a tendency that the compression stress value is increased by shortening a time necessary for ion exchange or by decreasing the temperature of an ion exchange solution.
• the thickness of the compression stress layer is preferably 10 ⁇ m or more, more preferably 15 ⁇ m or more, more preferably 20 ⁇ m or more, particularly preferably 30 ⁇ m or more.
• the thickness of the compression stress layer becomes larger, the tempered glass is more hardly cracked even when the tempered glass has a deep flaw, and a variation in the mechanical strength of the tempered glass becomes smaller. Meanwhile, as the thickness of the compression stress layer increases, it becomes more difficult to cut the tempered glass. In addition, there is a risk that a tensile stress inside the tempered glass may increase excessively to increase a dimensional change at the time of tempering. Accordingly, the thickness of the compression stress layer is preferably 60 ⁇ m or less.
• the thickness of the compression stress layer is increased by increasing the content of K 2 O or P 2 O 5 in the glass composition or by decreasing the content of SrO or BaO in the glass composition. Further, there is a tendency that the thickness of the compression stress layer is increased by lengthening a time necessary for ion exchange or by increasing the temperature of an ion exchange solution.
• the tempered glass of the present invention has a density of preferably 2.6 g/cm 3 or less, more preferably 2.55 g/cm 3 or less, more preferably 2.50 g/cm 3 or less, more preferably 2.48 g/cm 3 or less, more preferably 2.46 g/cm 3 or less, particularly preferably 2.45 g/cm 3 or less.
• the density is easily reduced by increasing the content of SiO 2 , B 2 O 3 , or P 2 O 5 in the glass composition or by decreasing the content of an alkali metal oxide, an alkaline earth metal oxide, ZnO, ZrO 2 , or TiO 2 in the glass composition.
• the tempered glass of the present invention has a thermal expansion coefficient in a temperature range of from 25 to 380° C. of 100 ⁇ 10 ⁇ 7 /° C. or less, preferably 95 ⁇ 10 ⁇ 7 /° C. or less, more preferably 90 ⁇ 10 ⁇ 7 /° C. or less, particularly preferably 85 ⁇ 10 ⁇ 7 /° C. or less.
• the thermal expansion coefficient is regulated within the above-mentioned range, the thermal expansion coefficient can be easily matched with that of a member such as a metal or an organic adhesive, which makes it easy to prevent the detachment of the member such as the metal or the organic adhesive.
• an increase in the content of an alkali metal oxide or alkaline earth metal oxide in the glass composition is likely to increase the thermal expansion coefficient, and conversely, a reduction in the content of the alkali metal oxide or alkaline earth metal oxide is likely to lower the thermal expansion coefficient.
• the tempered glass of the present invention has a temperature at 10 4.0 dPa ⁇ s of 1,300° C. or less, preferably 1,280° C. or less, more preferably 1,250° C. or less, more preferably 1,220° C. or less, particularly preferably 1,200° C. or less.
• a burden on a forming facility is reduced more, the forming facility has a longer life, and consequently, the manufacturing cost of the tempered glass is more likely to be reduced.
• the temperature at 10 4.0 dPa ⁇ s is easily decreased by increasing the content of an alkali metal oxide, an alkaline earth metal oxide, ZnO, B 2 O 3 , or TiO 2 or by reducing the content of SiO 2 or Al 2 O 3 .
• the tempered glass of the present invention has a temperature at 10 2.5 dPa ⁇ s of 1,650° C. or less, preferably 1,600° C. or less, more preferably 1,580° C. or less, particularly preferably 1,550° C. or less.
• a temperature at 10 2.5 dPa ⁇ s becomes lower, melting at lower temperature can be carried out, and hence a burden on glass manufacturing equipment such as a melting furnace is reduced more, and the bubble quality of glass is improved more easily. That is, as the temperature at 10 2.5 dPa ⁇ s becomes lower, the manufacturing cost of the tempered glass is more likely to be reduced.
• the “temperature at 10 2.5 dPa ⁇ s” can be measured by, for example, a platinum sphere pull up method.
• the temperature at 10 2.5 dPa ⁇ s corresponds to a melting temperature.
• an increase in the content of an alkali metal oxide, alkaline earth metal oxide, ZnO, B 2 O 3 , or TiO 2 in the glass composition or a reduction in the content of SiO 2 or Al 2 O 3 is likely to lower the temperature at 10 2.5 dPa ⁇ s.
• the tempered glass of the present invention has a liquidus temperature of 1,200° C. or less, preferably 1,150° C. or less, more preferably 1,100° C. or less, more preferably 1,080° C. or less, more preferably 1,050° C. or less, more preferably 1,020° C. or less, particularly preferably 1,000° C. or less. It should be noted that as the liquidus temperature becomes lower, the denitrification resistance and formability are improved more. It should be noted that the liquidus temperature is easily decreased by increasing the content of Na 2 O, K 2 O, or B 2 O 3 in the glass composition or by reducing the content of Al 2 O 3 , Li 2 O, MgO, ZnO, TiO 2 , or ZrO 2 .
• the tempered glass of the present invention has a liquidus viscosity of preferably 10 4.0 dPa ⁇ s or more, more preferably 10 4.4 dPa ⁇ s or more, more preferably 10 4.8 dPa ⁇ s or more, more preferably 10 5.0 dPa ⁇ s or more, more preferably 10 5.3 dPa ⁇ s or more, more preferably 10 5.5 dPa ⁇ s or more, more preferably 10 5.7 dPa ⁇ s or more, more preferably 10 5.8 dPa ⁇ s or more, particularly preferably 10 6.0 dPa ⁇ s or more. It should be noted that as the liquidus viscosity becomes higher, the denitrification resistance and formability are improved more.
• liquidus viscosity is easily increased by increasing the content of Na 2 O or K 2 O in the glass composition or by reducing the content of Al 2 O 3 , Li 2 O, MgO, ZnO, TiO 2 , or ZrO 2 in the glass composition.
• the tempered glass of the present invention has a Young's modulus of 65 GPa or more, preferably 69 GPa or more, more preferably 71 GPa or more, more preferably 75 GPa or more, particularly preferably 77 GPa or more.
• Young's modulus increases, the tempered glass is less liable to deflect, and in its use in a touch panel display or the like, the amount of deformation of the tempered glass reduces even when the surface of the tempered glass is strongly pressed with a pen or the like. As a result, it becomes easier to prevent a situation in which the tempered glass is brought into contact with a liquid crystal device located behind the tempered glass to cause a display failure.
• the amount of deformation with respect to a stress to be generated at the time of tempering treatment reduces, and hence a dimensional change between before and after tempering treatment is reduced.
• a tempered glass sheet of the present invention comprises the tempered glass described above.
• technical features (suitable characteristics, suitable component ranges, and the like) of the tempered glass sheet of the present invention are the same as the technical features of the tempered glass of the present invention. Accordingly, detailed descriptions of the technical features of the tempered glass sheet of the present invention are omitted here.
• the tempered glass sheet of the present invention has a fictive temperature Tf of 500° C. or more, preferably from 520° C. to 700° C., particularly preferably from 550° C. to 750° C.
• Tf fictive temperature
• the structure of the tempered glass can be more easily relaxed, and hence a dimensional change between before and after tempering treatment reduces. As a result, the dimensional accuracy of the tempered glass sheet can be increased.
• the fictive temperature Tf can be controlled by adjusting forming conditions in an overflow down-draw method.
• the surface of the tempered glass sheet of the present invention has an average surface roughness (Ra) of preferably 10 ⁇ or less, more preferably 8 ⁇ or less, more preferably 6 ⁇ or less, more preferably 4 ⁇ or less, more preferably 3 ⁇ or less, particularly preferably 2 ⁇ or less.
• Ra average surface roughness
• the average surface roughness (Ra) refers to a value measured by a method in conformity with SEMI D7-97 “FPD Glass Substrate Surface Roughness Measurement Method.”
• the tempered glass sheet of the present invention has a length dimension of 500 mm or more, preferably 700 mm or more, particularly preferably 1,000 mm or more and a width dimension of 500 mm or more, preferably 700 mm or more, particularly preferably 1,000 mm or more.
• An increase in the size of the tempered glass sheet enables the tempered glass sheet to be suitably used as a cover glass for the display portion of the display of a large-size TV or the like.
• the upper limit range of the sheet thickness of the tempered glass sheet of the present invention is 2.0 mm or less, preferably 1.5 mm or less, more preferably 1.3 mm or less, more preferably 1.1 mm or less, more preferably 1.0 mm or less, more preferably 0.8 mm or less, particularly preferably 0.7 mm or less. Meanwhile, when the sheet thickness is excessively small, desired mechanical strength is difficult to obtain. Thus, the sheet thickness is 0.1 mm or more, preferably 0.2 mm or more, more preferably 0.3 mm or more, more preferably 0.4 mm or more, particularly preferably 0.5 mm or more.
• a glass to be tempered of the present invention is a glass to be subjected to tempering treatment, comprising as a glass composition, in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 2% of Li 2 O, and 5 to 25% of Na 2 O, and being substantially free of As 2 O 3 , Sb 2 O 3 , PbO, and F.
• a glass composition in terms of mass %, 50 to 80% of SiO 2 , 10 to 30% of Al 2 O 3 , 0 to 6% of B 2 O 3 , 0 to 2% of Li 2 O, and 5 to 25% of Na 2 O, and being substantially free of As 2 O 3 , Sb 2 O 3 , PbO, and F.
• the glass to be tempered of the present invention has a dimensional change rate S between before and after tempering treatment (immersion in a KNO 3 molten salt at 440° C. for 6 hours) of from ⁇ 1,000 ppm to +1,000 ppm, preferably from ⁇ 500 ppm to +800 ppm, more preferably from ⁇ 200 ppm to +600 ppm, particularly preferably from ⁇ 100 ppm to +500 ppm.
• the dimensional change rate S between before and after tempering treatment can be made close to 0 to the extent possible by increasing the Young's modulus, increasing the fictive temperature Tf, reducing the compression stress value of the compression stress layer, and reducing the thickness of the compression stress layer.
• the compression stress value of a compression stress layer in a surface thereof be 300 MPa or more and the thickness of the compression stress layer be 10 ⁇ m or more, it is more preferred that the compression stress of the surface thereof be 600 MPa or more and the thickness of the compression stress layer be 30 ⁇ m or more, and it is particularly preferred that the compression stress of the surface thereof be 700 MPa or more and the thickness of the compression stress layer be 30 ⁇ m or more.
• the temperature of the KNO 3 molten salt is preferably from 400 to 550° C.
• the ion exchange time is preferably from 1 to 10 hours, particularly preferably from 2 to 8 hours.
• the compression stress layer can be properly formed easily.
• the glass to be tempered of the present invention has the above-mentioned glass composition, and hence the compression stress value and thickness of the compression stress layer can be increased without using a mixture of a KNO 3 molten salt and a NaNO 3 molten salt or the like.
• the glass to be tempered of the present invention has a fictive temperature Tf of 500° C. or more, preferably from 520° C. to 700° C., particularly preferably from 550° C. to 750° C.
• Tf fictive temperature
• the structure of the tempered glass can be more easily relaxed, and hence a dimensional change between before and after tempering treatment reduces. As a result, the dimensional accuracy of the tempered glass sheet can be increased.
• the fictive temperature Tf can be controlled by adjusting forming conditions in an overflow down-draw method.
• a cooling rate is preferably increased and a sheet drawing rate is preferably increased.
• a sheet drawing rate is preferably increased.
• an overflow down-draw method is adopted as a forming method and the glass is cut at a position spaced apart downwardly by 1,000 mm or more, preferably 2,000 mm or more, particularly preferably 3,000 mm or more from the lower end of a forming trough used in the overflow down-draw method.
• a crack generation rate before tempering treatment at a load of 1,000 gf is preferably 99% or less, more preferably 90% or less, more preferably 80% or less, more preferably 70% or less, more preferably 60% or less, more preferably 65% or less, particularly preferably 50% or less.
• the crack generation rate reduces, a surface flaw is less liable to be created on the tempered glass, and hence the mechanical strength of the tempered glass is less liable to lower.
• the mechanical strength is less liable to vary.
• the crack generation rate is low, a lateral crack is hardly generated at the time of post-tempering cutting such as post-tempering scribe cutting, and hence the post-tempering cutting can be easily performed appropriately. As a result, the manufacturing cost of a device can be easily reduced.
• the glass to be tempered of the present invention be not devitrified at a contact interface when the glass to be tempered has a viscosity of 10 4.5 dPa ⁇ s and is brought into contact for 48 hours with a material for a forming trough (such as dense zircon or alumina, in particular, alumina) to be used in an overflow down-draw method.
• a material for a forming trough such as dense zircon or alumina, in particular, alumina
• the glass to be tempered, tempered glass, and tempered glass sheet of the present invention can be produced as described below.
• glass raw materials which have been blended so as to have the above-mentioned glass composition, are loaded in a continuous melting furnace, are melted by heating at from 1,500 to 1,600° C., and are fined. After that, the resultant is fed to a forming apparatus, is formed into a sheet shape or the like, and is annealed. Thus, a glass sheet or the like can be produced.
• An overflow down-draw method is preferably adopted as a method of forming the glass sheet.
• the overflow down-draw method is a method by which a high-quality glass sheet can be produced in a large amount, and by which even a large-size glass sheet can be easily produced.
• the fictive temperature Tf of the glass sheet can be easily increased.
• alumina or dense zircon is used as a forming trough.
• the glass to be tempered of the present invention has satisfactory compatibility with alumina and dense zircon, in particular, alumina (hardly reacts with the forming trough to generate bubbles, glass stones, or the like).
• forming methods other than the overflow down-draw method may also be adopted.
• forming methods such as a float method, a down draw method (such as a slot down method or a re-draw method), a roll out method, and a press method may be adopted.
• the resultant glass to be tempered is subjected to tempering treatment, thereby being able to produce a tempered glass.
• the resultant tempered glass may be cut into pieces having predetermined sizes before the tempering treatment or after the tempering treatment.
• the tempering treatment is preferably ion exchange treatment.
• Conditions for the ion exchange treatment are not particularly limited, and optimum conditions may be selected in view of, for example, the viscosity properties, applications, thickness, inner tensile stress, and dimensional change of glass.
• the ion exchange treatment can be performed, for example, by immersing glass in a KNO 3 molten salt at 400 to 550° C. for 1 to 8 hours. Particularly when the ion exchange of K ions in the KNO 3 molten salt with Na components in the glass is performed, it is possible to form efficiently a compression stress layer in a surface of the glass.
• Tables 1 to 34 show Examples of the present invention (sample Nos. 1 to 204).
• each of the samples in the tables was produced as described below.
• glass raw materials were blended so as to have the glass composition in the tables, and melted at 1,600° C. for 8 hours using a platinum pot. After that, the resultant molten glass was poured onto a carbon sheet so as to be formed into a sheet shape.
• glass raw materials were blended so as to have the glass composition in the tables, and melted at 1,600° C. for 21 hours using a platinum pot. After that, the resultant molten glass was poured onto a carbon sheet so as to be formed into a sheet shape.
• the obtained glass sheets were evaluated for various characteristics.
• the density ⁇ is a value obtained through measurement by a known Archimedes method.
• the thermal expansion coefficient ⁇ is a value obtained through measurement of an average thermal expansion coefficient in a temperature range of from 25 to 380° C. using a dilatometer.
• the Young's modulus E is a value obtained through measurement by a well-known resonance method.
• strain point Ps and the annealing point Ta are values obtained through measurement based on a method of ASTM C336.
• the softening point Ts is a value obtained through measurement based on a method of ASTM C338.
• the temperatures at the viscosities at high temperature of 10 4.0 dPa ⁇ s, 10 3.0 dPa ⁇ s, and 10 2.5 dPa ⁇ s are values obtained through measurement by a platinum sphere pull up method.
• the liquidus temperature TL is a value obtained through measurement of a temperature at which crystals of glass are deposited after glass powder that passes through a standard 30-mesh sieve (sieve opening: 500 ⁇ m) and remains on a 50-mesh sieve (sieve opening: 300 ⁇ m) is placed in a platinum boat and then kept for 24 hours in a gradient heating furnace.
• the liquidus viscosity is a value obtained through measurement of a viscosity of glass at the liquidus temperature by a platinum sphere pull up method.
• the crack generation rate was measured as described below. First, in a constant temperature and humidity chamber kept at a humidity of 30% and a temperature of 25° C., a Vickers indenter set to a load of 1,000 gf is driven into a glass surface (optically polished surface) for 15 seconds, and 15 seconds after that, the number of cracks generated from the four corners of the indentation is counted (4 per indentation at maximum). The indenter was driven in this manner 20 times, the total number of generated cracks was determined, and then the crack generation rate was determined by the following expression: total number of generated cracks/80 ⁇ 100.
• the compatibility with alumina was evaluated as described below. Each of the samples having a viscosity of 10 4.5 dPa ⁇ s was brought into contact with alumina for 48 hours. After that, a contact interface between each of the samples and alumina was observed, an evaluation was made by marking a case where no devitrified crystal is precipitated with Symbol “ ⁇ ”, and marking a case where a devitrified crystal is precipitated with Symbol “x”.
• each of Samples Nos. 1 to 204 has a density of 2.54 g/cm 3 or less and a thermal expansion coefficient of from 88 to 100 ⁇ 10 ⁇ 7 /° C., thus being suitable as a material for a tempered glass, that is, a glass to be tempered.
• each of the samples has a liquidus viscosity of 10 4.4 dPa ⁇ s or more, and hence can be formed into a sheet shape by an overflow down-draw method.
• each of the samples has a temperature at 10 2.5 dPa ⁇ s of 1,738° C. or less, and hence is considered to allow the production of a glass sheet in a large amount at low cost with high productivity.
• the glass composition in the surface layer of the glass differs microscopically between before and after tempering treatment, but when the glass is observed as a whole, the glass composition does not differ substantially.
• both surfaces of each of the samples shown in Tables 1 to 8 were subjected to optical polishing. After that, each of the samples was subjected to ion exchange treatment by being immersed in a KNO 3 molten salt (fresh KNO 3 molten salt) at 440° C. for 6 hours. In addition, both surfaces of each of the samples shown in Tables 9 to 34 were subjected to optical polishing. After that, each of the samples was subjected to ion exchange treatment by being immersed in a KNO 3 molten salt (fresh KNO 3 molten salt) at 430° C. for 4 hours. The surfaces of each of the samples were washed after the ion exchange treatment.
• the compression stress value (CS) and thickness (DOL) of the compression stress layer in the surfaces were calculated on the basis of the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by TOSHIBA CORPORATION) and intervals therebetween.
• the refractive index and optical elastic constant of each of the samples were defined as 1.51 and 30 [(nm/cm)/MPa], respectively.
• the compression stress layer in a surface thereof had a compression stress value of 823 MPa or more and a thickness of 27 ⁇ m or more.
• the dimensional change shows a positive value ⁇ L1
• T2 lower than the fictive temperature Tf
• the dimensional change shows a negative value ⁇ L2.
• the obtained glass sheet was subjected to ion exchange treatment by being immersed in a KNO 3 molten salt (KNO 3 molten salt having no history of being used) at 440° C. for 6 hours.
• the obtained glass sheet had a fictive temperature Tf of 651° C. and a dimensional change rate S between before and after tempering treatment of 525 ppm. It should be noted that when each of Samples Nos. 1 to 38 and 40 to 204 of Tables 1 to 34 is similarly evaluated, the glass sheet to be obtained is considered to have a fictive temperature Tf of 550° C. or more and a dimensional change rate S between before and after tempering treatment of 1,000 ppm or less.
• the tempered glass and tempered glass sheet of the present invention are suitable for a cover glass of a cellular phone, a digital camera, a PDA, or the like, or a glass substrate for a touch panel display or the like. Further, the tempered glass and tempered glass sheet of the present invention can be expected to find use in applications requiring high mechanical strength, for example, a window glass, a substrate for a magnetic disk, a substrate for a flat panel display, a cover glass for a solar battery, a cover glass for a solid image pick-up element, and tableware, in addition to the above-mentioned applications.

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