Provided is a silica glass member which exhibits high optical transparency to vacuum ultraviolet light and has a low thermal expansion coefficient of 4.010.sup.7/K or less at near room temperature, particularly a silica glass member which is suitable as a photomask substrate to be used in a double patterning exposure process using an ArF excimer laser (193 nm) as a light source. The silica glass member is used in a photolithography process using a vacuum ultraviolet light source, in which the fluorine concentration is 1 wt % or more and 5 wt % or less, and the thermal expansion coefficient at from 20 C. to 50 C. is 4.010.sup.7/K or less.

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.

Method and apparatus are provided for the controlled transport of glass sheets (13) or glass ribbons (15) undergoing heating and/or cooling (e.g., thermal tempering) by conduction more than convection. The controlled transport is achieved by applying a gas-based force (17,19,21) to the glass sheet (13) or glass ribbon (15). The gas-based force (17,19,21) can move the glass sheet (13) or glass ribbon (15) in a desired direction and/or cause it to acquire a desired orientation. The gas-based force (17,19,21) can also cause the glass sheet (13) or glass ribbon (15) to retain a desired position and/or a desired orientation. The gas-based force (17,19,21) can be applied to the glass sheet (13) or glass ribbon (15) continuously or intermittently. Systems for transitioning a glass sheet (13) or a glass ribbon (15) between a heating zone (27) and a quench zone (31) are also discussed.

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.

A glass composition formed of a glass frit including P.sub.2O.sub.5, SiO.sub.2, B.sub.2O.sub.3, Al.sub.2O.sub.3, ZrO.sub.2 and group I-based oxide, wherein P.sub.2O.sub.5 is contained in an amount of 20 wt % to 40 wt % based on a total weight of the glass frit, SiO.sub.2 is contained in an amount of to wt % to 30 wt % based on the total weight of the glass frit, B.sub.2O.sub.3 is contained in an amount of 3 wt % to 20 wt % based on the total weight of the glass frit, Al.sub.2O.sub.3 is contained in an amount of 7 to 24 wt % based on the total weight of the glass frit, ZrO.sub.2 is contained in an amount of 1 wt % to 7 wt % based on the total weight of the glass frit, and the group I-based oxide is contained in an amount of 7 wt % to 28 wt % based on the total weight of the glass frit.

A glass composition formed of glass frit including P.sub.2O.sub.5, TiO.sub.2 and group I-based oxide, wherein P.sub.2O.sub.5 is contained in an amount of 20 wt % to 30 wt % based on a total weight of the glass frit, wherein TiO.sub.2 is contained in an amount of 10 wt % to 20 wt % based on the total weight of the glass frit, and wherein the group I-based oxide is contained in an amount of 15 wt % to 30 wt % based on the total weight of the glass frit.

There is provided a tempered glass plate, wherein a thickness of the tempered glass plate is less than or equal to 2.7 mm, wherein on a surface of the tempered glass plate, a plurality of stress marks are formed, wherein a distance between closest stress marks of the plurality of stress marks is less than or equal to 20 mm, wherein the surface of the tempered glass plate includes a first virtual circle that is formed by connecting points that are separated from a center of one of the plurality of stress marks by 2.5 mm, wherein the tempered glass plate includes a non elastic-wave region that is not affected by an elastic-wave generated during fracturing, and wherein, in the non elastic-wave region, an average number of cracks that exist in the first virtual circle is greater than or equal to 3.4.

The present invention generally relates to a process for fabricating Chloro Alkali Phosphate Doped/Codoped by rare earth ions for optical laser amplifiers. The process includes mixing 38-42 wt. % of Phosphorus pentoxide (P.sub.2O.sub.5), 28-32 wt. % of Zinc oxide (ZnO), 9-11 wt. % of Barium fluoride (BaF.sub.2), 17-19 wt. % of Lithium chloride (LiCl), and 1-3 wt. % of Lead(II) fluoride (PbF.sub.2); filling a silica, platinum, and alumina crucible to the mixture; heating the mixture upon increasing a furnace temperature to 1000-1050 C. at a rate of 10 C. per minute and maintaining it for two hours to melt the glass; and pouring the glass melt into a preheated stainless steel mold at 350 C. and transferring the mold to a holding furnace heated to 350-370 C. and annealing for two hours thereby cooling to room temperature to obtain Chloro Alkali Phosphate matrix glass that is undoped, doped, or codoped with high thermal stability.

The invention relates to a method of heating a glass sheet for tempering. It comprises conveying the glass sheet on top of rollers in a roller-hearth furnace, heating the glass sheet in the roller-hearth furnace to a transfer temperature at which the glass sheet is transferred into an air support furnace. The glass sheet, while resting on an air cushion, is carried on an air support table and the glass sheet is heated in the air support furnace to a tempering temperature. The transfer temperature is not lower than 620 C. and not higher than 675 C. and the tempering temperature is not lower than 650 C. and not higher than 720 C.