An apparatus for thermally strengthening a glass sheet includes a first heat sink surface, a second heat sink surface separated from said first heat sink surface by a gap between the heat sink surfaces of distance g, and a liquid feed structure positioned to be able to feed a liquid to the gap, wherein the distance g is sufficiently small relative to a thickness t of a glass sheet to be processed such that when a sheet of thickness t is positioned within the gap of distance g, thermal transfer from a first surface of the sheet facing the first heat sink surface is more than 20%, 30%, 40% or 50% or more by conduction from the first surface of the sheet through the liquid to the first heat sink surface.

A process of strengthening a glass sheet by cooling a sheet or portion of a sheet, the sheet comprising or consisting of a glass having a glass transition temperature, given in units of C., of T, wherein the cooling is performed starting with the sheet at a temperature above T, with more than 20%, 30%, 40% or 50% or more of said cooling, at some point during said cooling, being by thermal conduction through a liquid to a heat sink surface comprising a solid.

A process of strengthening a glass sheet by cooling a sheet or portion of a sheet, the sheet comprising or consisting of a glass having a glass transition temperature, given in units of C., of T, wherein the cooling is performed starting with the sheet at a temperature above T, with more than 20%, 30%, 40% or 50% or more of said cooling, at some point during said cooling, being by thermal conduction through a liquid to a heat sink surface comprising a solid.

The present invention provides an on-line method for stabilizing surface compressive stress of chemically-tempered glass, which comprises the steps of: placing glass to be tempered together with a stabilizer in a tempering furnace containing a molten salt bath for glass tempering; and after reacting at a temperature for a period of time, removing the glass and the stabilizer from the tempering furnace. The stabilizer is capable of chemically reacting with impurity ions in the molten salt bath for glass tempering, to remove the impurity ions in the molten salt bath. Therefore, the presence of the stabilizer allows the impurity ion content in the molten salt bath for glass tempering to be stable without gradual accumulation.

The present invention provides an on-line method for stabilizing surface compressive stress of chemically-tempered glass, which comprises the steps of: placing glass to be tempered together with a stabilizer in a tempering furnace containing a molten salt bath for glass tempering; and after reacting at a temperature for a period of time, removing the glass and the stabilizer from the tempering furnace. The stabilizer is capable of chemically reacting with impurity ions in the molten salt bath for glass tempering, to remove the impurity ions in the molten salt bath. Therefore, the presence of the stabilizer allows the impurity ion content in the molten salt bath for glass tempering to be stable without gradual accumulation.

The present invention is directed to a kind of machinable glass ceramic which can be chemically toughened. The machinable and chemically toughenable glass ceramic, which comprises, as represented by weight percentage based on the following compositions, 25-75 wt % of SiO.sub.2, 6-30 wt % of Al.sub.2O.sub.3, 0.1-30 wt % of Na.sub.2O, 0-15 wt % of K.sub.2O, 0-30 wt % of B.sub.2O.sub.3, 4-35 wt % of MgO, 0-4 wt % of CaO, 1-20 wt % of F, 0-10 wt % of ZrO.sub.2, 0.1-10 wt % of P.sub.2O.sub.5, 0-1 wt % of CeO.sub.2 and 0-1 wt % of SnO.sub.2, wherein P.sub.2O.sub.5+Na.sub.2O>3 wt %, and Al.sub.2O.sub.3+Na.sub.2O+P.sub.2O.sub.5>17 wt %. Mica crystalline phase can be formed in the glass ceramic and the glass ceramic can be chemically toughened by one step, two steps or multiple steps with depth of K-ion layer of at least 15 m and surface compress stress of at least 300 MPa. The profile on depth of the ion exchange layer follows the complementary error function. Hardness can be improved by at least 20% after chemical toughening. The dimension deviation ratio is less than 0.06% by ion-exchanging.

The present invention is directed to a kind of machinable glass ceramic which can be chemically toughened. The machinable and chemically toughenable glass ceramic, which comprises, as represented by weight percentage based on the following compositions, 25-75 wt % of SiO.sub.2, 6-30 wt % of Al.sub.2O.sub.3, 0.1-30 wt % of Na.sub.2O, 0-15 wt % of K.sub.2O, 0-30 wt % of B.sub.2O.sub.3, 4-35 wt % of MgO, 0-4 wt % of CaO, 1-20 wt % of F, 0-10 wt % of ZrO.sub.2, 0.1-10 wt % of P.sub.2O.sub.5, 0-1 wt % of CeO.sub.2 and 0-1 wt % of SnO.sub.2, wherein P.sub.2O.sub.5+Na.sub.2O>3 wt %, and Al.sub.2O.sub.3+Na.sub.2O+P.sub.2O.sub.5>17 wt %. Mica crystalline phase can be formed in the glass ceramic and the glass ceramic can be chemically toughened by one step, two steps or multiple steps with depth of K-ion layer of at least 15 m and surface compress stress of at least 300 MPa. The profile on depth of the ion exchange layer follows the complementary error function. Hardness can be improved by at least 20% after chemical toughening. The dimension deviation ratio is less than 0.06% by ion-exchanging.

A glass article includes a glass composition including mole percent (mol %) to 70 mol % of SiO.sub.2, 5 mol % to 15 mol % of Al.sub.2O.sub.3, 5 mol % to 15 mol % of Na.sub.2O, greater than 0 mol % and equal to or less than 5 mol % of K.sub.2O, 5 mol % to 15 mol % of Li.sub.2O, and greater than 0 mol % and equal to or less than 5 mol % of MgO, and satisfying Relation (1) below:

0.1Al.sub.2O.sub.3/(sum of Na.sub.2O,K.sub.2O, and Li.sub.2O)0.7(1),

where Al.sub.2O.sub.3, Na.sub.2O, K.sub.2O, and Li.sub.2O in the Relation (1) denote contents (mol %) of Al.sub.2O.sub.3, Na.sub.2O, K.sub.2O, and Li.sub.2O, respectively, in the glass composition, and the glass article has a thickness of 100 micrometers (m) or less.

A glass article includes a glass composition including mole percent (mol %) to 70 mol % of SiO.sub.2, 5 mol % to 15 mol % of Al.sub.2O.sub.3, 5 mol % to 15 mol % of Na.sub.2O, greater than 0 mol % and equal to or less than 5 mol % of K.sub.2O, 5 mol % to 15 mol % of Li.sub.2O, and greater than 0 mol % and equal to or less than 5 mol % of MgO, and satisfying Relation (1) below:

0.1Al.sub.2O.sub.3/(sum of Na.sub.2O,K.sub.2O, and Li.sub.2O)0.7(1),

where Al.sub.2O.sub.3, Na.sub.2O, K.sub.2O, and Li.sub.2O in the Relation (1) denote contents (mol %) of Al.sub.2O.sub.3, Na.sub.2O, K.sub.2O, and Li.sub.2O, respectively, in the glass composition, and the glass article has a thickness of 100 micrometers (m) or less.

A window includes a base region and a compressive stress region disposed on the base region. The compressive stress region includes Li.sup.+, Na.sup.+, and K.sup.+ ions. The compressive stress region includes a first compressive stress portion in which a concentration of the K.sup.+ ions decreases, a concentration of Na.sup.+ ions increases, and a concentration of the Li.sup.+ ions increases, from a surface of the window toward the base region. A second compressive stress portion is adjacent to the first compressive stress portion. In the second compressive stress portion, the concentration of the Na.sup.+ ion decreases and the concentration of the Li.sup.+ ion increases, from the first compressive stress portion toward the base region. The window thereby has a high surface compressive stress value and impact resistance.