Provided is an alkali-free glass substrate having a high strain point and excellent bubble count, and a method for manufacturing the alkali-free glass substrate. The method includes: a batch preparing process of preparing a raw material batch so as to obtain alkali-free glass containing, in mass %, 50 to 80% of SiO.sub.2, 15 to 30% of Al.sub.2O.sub.3, 0 to 4.5% of B.sub.2O.sub.3, 0 to 10% of MgO, 0 to 15% of CaO, 0 to 10% of SrO, 0 to 15% of BaO, 0 to 5% of ZnO, 0 to 5% of ZrO.sub.2, 0 to 5% of TiO.sub.2, 0 to 15% of P.sub.2O.sub.5 and 0 to 0.5% of SnO.sub.2 as a glass composition; a melting process of melting the prepared raw material batch; a fining process of fining the molten glass; and a forming process of forming the fined glass into a sheet shape. The raw material batch is melted such that a bubble enlarging temperature of the obtained glass is lower than a maximum temperature of the fining process.

A method of forming a glass sheet comprises: (a) forming a ribbon of glass from molten glass with a pair of forming rollers; (b) reducing horizontal temperature variability of the ribbon of glass to be 10° C. or less across 80 percent of an entire width of the ribbon of glass before the ribbon of glass cools to a glass transition temperature; (c) controlling a cooling rate of the ribbon of glass while the ribbon of glass moves vertically downward within a setting zone such that the ribbon of glass has a first average cooling rate before the ribbon of glass cools to the glass transition temperature and a second average cooling rate after the ribbon of glass cools to the glass transition temperature, the first average cooling rate being less than the second average cooling rate; and (d) separating a glass sheet from the ribbon of glass.

A manufacturing method for a band-shaped glass includes a forming step, which forms a band-shaped glass, an annealing step, which performs an annealing treatment on the band-shaped glass, a cooling step, which cools the annealed band-shaped glass, a direction-changing step, which changes a feeding direction of the cooled band-shaped glass from a longitudinal direction to a horizontal direction, and a horizontal conveying step, which conveys the band-shaped glass in the horizontal direction while supporting the band-shaped glass at a horizontal conveyance part. In the horizontal conveying step, the band-shaped glass is conveyed in the horizontal direction while a first propulsion for driving the conveyance in the horizontal direction is provided at both sides in the width direction of the band-shaped glass by the horizontal conveyance part, the first propulsion being larger than a second propulsion provided at a center in the width direction of the band-shaped glass.

Described herein are alkali-free, boroalumino silicate glasses exhibiting desirable physical and chemical properties for use as substrates in flat panel display devices, such as, active matrix liquid crystal displays (AMLCDs) and active matrix organic light emitting diode displays (AMOLEDs). In accordance with certain of its aspects, the glasses possess good dimensional stability as a function of temperature.

According to one embodiment, an apparatus for forming a glass ribbon may include a forming wedge disposed in a housing and including a pair of downwardly inclined forming surfaces converging at a root. A plurality of heating cartridges may be positioned in ports of the housing. Each heating cartridge may include a heat directing surface that is oriented at an angle of greater than about 90° with respect to a bottom surface of the heating cartridge. The heat directing surface may include at least one heating element positioned adjacent to the heat directing surface. The heating cartridge may be positioned such that the heat directing surface faces the forming wedge and an upper edge of the heat directing surface is positioned above the root to direct heat from the heat directing surface towards the root of the forming wedge.

A forming apparatus for forming a glass ribbon is provided. The forming apparatus has an axial direction extending from a first end to a second end thereof. The first end is located on an inlet side from which molten glass is supplied. The forming apparatus includes a first protruding portion and a second protruding portion that are disposed at a top thereof and extend from the first end to the second end. A channel is provided between the first protruding portion and the second protruding portion. The molten glass flows within the channel from the first end toward the second end. In a top view, a channel width of the channel continuously decreases toward the second end in a vicinity of the second end and becomes 0 (zero) at the second end. The channel width is in a direction perpendicular to the axial direction.

A refractory object may include a zircon body that may include at least about 0.1 wt. % and not greater than about 5.5 wt. % of an Al.sub.2O.sub.3 containing component for a total weight of the zircon body. The zircon body may further include at least about 25 wt. % and not greater than about 35 wt. % of a SiO.sub.2 component for a total weight of the zircon body.

Apparatuses for making a laminated glass ribbon may include an upper forming body including an outer forming surface bounded by a pair of upper dams, and a lower forming body disposed downstream of the upper forming body and including an outer forming surface spaced from the outer forming surface of the upper forming body by an interior gap. An edge guide may be disposed along an interior upper dam wall and spaced apart in the interior gap from the lower forming body. Surfaces exterior to the outer forming surfaces of the upper and lower forming bodies may abut and be joined. A formed glass ribbon having a core glass layer and a pair of clad glass layers may include inner and outer portions that have substantially equal thickness ratios based on a glass core layer thickness compared to a combined glass cladding layer thickness in each portion.

Disclosed herein are laminated glass articles having a hard scratch resistant outer surface. In some embodiments, the laminated glass article includes a glass core layer and a glass clad layer. In some embodiments, the laminated glass article includes a glass core layer sandwiched between two glass clad layers. In some embodiments, the clad glass is selected from the group of consisting of: aluminate glasses; oxynitride glasses; rare earth/transition metal glasses; beryl glasses; and glasses containing lithium, zirconium, or both lithium and zirconium. Such glass compositions can thus be used in forming the clad layer.

Described herein are glass forming apparatuses with cooled muffle assemblies and methods for using the same to form glass ribbons. According to one embodiment, a muffle assembly for a fusion forming apparatus may include a muffle frame comprising a back wall, a front wall opposite the back wall, and a pair of sidewalls joining the front wall to the back wall in a closed-loop. At least one first cooling tube may extend through the back wall and the front wall across the closed-loop. At least one second cooling tube may extend through the back wall and the front wall across the closed loop such that the at least one second cooling tube is spaced apart from and parallel with the at least one first cooling tube.