A method for treating a lead-containing glass that makes it possible to limit the migration of the lead contained in this glass, the method successively comprising the following distinct steps: a step of placing the lead-containing glass in contact with a solution comprising perchloric acid; a step of heat treatment of the glass at a temperature less than or equal to the glass transition temperature of the glass.

Lithium silicate glass ceramics and precursors thereof are described, which comprise copper and are characterized by very good mechanical and optical properties and can be used in particular as restorative materials in dentistry.

Lithium silicate glass ceramics and precursors thereof are described, which contain tin and are characterized by very good mechanical and optical properties and can be used in particular as restorative materials in dentistry.

Glass ceramic material for the production of synthetic stones in fashion jewellery and jewellery, having excellent mechanical properties, chemical and heat resistance, harmless due to absence of lead, arsenic and cadmium compounds, available in a broad scale of colour designs, imitating faithfully natural precious stones thanks to high content of spinel crystalline phase and lowered content of SiO.sub.2, consisting of (in weight %):

20-40% SiO.sub.2,
1.5-10% B.sub.2O.sub.3,
20-35% Al.sub.2O.sub.3,
0.1-20% MgO,
0.1-20% ZnO,
the content of MgO+ZnO being at least 10%,
preferably also
0-15% TiO.sub.2,
0.1-15% ZrO.sub.2,
the content of TiO.sub.2+ZrO.sub.2 being at least 5%,
more preferably also
0-20% of colouring additives in the form of CoO, NiO, CuO, Fe.sub.2O.sub.3, MnO.sub.2, Cr.sub.2O.sub.3, V.sub.2O.sub.5, Pr.sub.2O.sub.3, CeO.sub.2, Nd.sub.2O.sub.3, Er.sub.2O.sub.3, AgO and Au.

The purpose of the present invention is to provide a chemically strengthened glass having excellent transparency and strength and being scratch resistant. The present invention pertains to a chemically strengthened glass that: has a compressive stress layer on the surface thereof; has a visible light transmittance of at least 70% when the thickness thereof is converted to 0.8 mm; has a surface compressive stress of at least 600 MPa; has a compressive stress depth of at least 80 μm; and contains a β-spodumene.

The present invention pertains to a glass for strengthening, that: has an average transmittance of at least 70% when converted to a thickness of 0.8 mm at a wavelength of 380-780 nm; has a haze value of no more than 0.7% when converted to a thickness of 0.8 mm in a C light source; has a Young's modulus of at least 85 GPa; has a fracture toughness value of at least 0.90 MPa.Math.m.sup.1/2; a thermal conductivity at 20° C. of at least 1.3 W/m.Math.K; and comprises a lithium aluminosilicate crystallized glass.

The present invention pertains to a glass for strengthening, that: has an average transmittance of at least 70% when converted to a thickness of 0.8 mm at a wavelength of 380-780 nm; has a haze value of no more than 0.7% when converted to a thickness of 0.8 mm in a C light source; has a Young's modulus of at least 85 GPa; has a fracture toughness value of at least 0.90 MPa.Math.m.sup.1/2; a thermal conductivity at 20° C. of at least 1.3 W/m.Math.K; and comprises a lithium aluminosilicate crystallized glass.

Provided is a crystallized glass, which has a high fracture toughness value, and besides, is excellent in transparency. The crystallized glass includes, in terms of mass%, 40% to 70% of SiO.sub.2, 5% to 40% of Al.sub.2O.sub.3, 2% to 25% of B.sub.2O.sub.3, 0% to 15% of MgO+ZnO, 0% to 20% of CaO+SrO+BaO, 0% to 8% of P.sub.2O.sub.5+TiO.sub.2+ZrO.sub.2, 1% to 20% of Na.sub.2O+K.sub.2O, and 0% to 6% of Li.sub.2O, has a crystallinity of from 1% to 50%, and has an average visible-light transmittance of 50% or more at a thickness of 0.8 mm and a wavelength of from 380 nm to 780 nm.

The present invention provides crystallized glass of three-dimensional shape for easily producing chemically strengthened glass of three-dimensional shape that resists damage and has exceptional transparency. This crystallized glass of three-dimensional shape:

contains crystals; has light transmittance in terms of a thickness of 0.8 mm of 80% or higher; and contains 45-74% SiO.sub.2, 1-30% Al.sub.2O.sub.3, 1-25% Li.sub.2O, 0-10% Na.sub.2O, 0-5% K.sub.2O, a total of 0-15% of SnO.sub.2 and/or ZrO.sub.2, and 0-12% P.sub.2O.sub.5, these amounts expressing the oxide-based mass percentage.

Disclosed are a miserite crystallized glass for an artificial tooth and a method for coloring same, the method enabling a production of a uniform shade without degrading the physical properties of a crystallized glass by means of simply adding a small amount of coloring additive powder when preparing the crystallized glass. A miserite crystallized glass for an artificial tooth according to the present invention is colored with any one of the shades in groups A, B, C and D of the Vita shade guide which is a tooth shade reference. The miserite crystallized glass has a miserite crystal phase as the main phase and comprises a hydroxyapatite crystal phase and a xonotlite crystal phase as additional phases.