An apparatus for making a glass ribbon can include a heating plane including a heat footprint facing the surface of an edge director. A projection of the heat footprint in a resultant direction of the heating plane within the heat footprint can intersect the surface of the edge director. In further embodiments, a fusion draw method of making a glass ribbon can include radiating heat within a heat footprint of a heating plane toward a surface of an edge director. At least a portion of the heating plane within the heat footprint can face the surface of the edge director so that the surface of the edge director is intersected with heat radiating from the heat footprint of the heating plane.

The present invention provides a glass substrate in which in a heat treatment step of sticking a silicon substrate and a glass substrate to each other, an alkali ion is hardly diffused into the silicon substrate, and a residual strain generated in the silicon substrate is small. A glass substrate of the present invention has: an average thermal expansion coefficient .sub.50/100 at 50 C. to 100 C. of 2.70 ppm/ C. to 3.20 ppm/ C.; an average thermal expansion coefficient .sub.200/300 at 200 C. to 300 C. of 3.45 ppm/ C. to 3.95 ppm/ C.; a value .sub.200/300/.sub.50/100 obtained by dividing the average thermal expansion coefficient .sub.200/300 at 200 C. to 300 C. by the average thermal expansion coefficient .sub.50/100 at 50 C. to 100 C. of 1.20 to 1.30; and a content of an alkali metal oxide being 0% to 0.1% as expressed in terms of a molar percentage based on oxides.

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 surface portions 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.

The present disclosure provides a device and a method with which flat glasses with particularly uniform thickness can be obtained. The methods are drawing methods in which a glass ribbon is drawn. In the method an aperture is used which allows a defined very small slit between the glass ribbon and the aperture also in the case of a change of the position of the glass ribbon.

A glass sheet includes a first major surface, a second major surface opposite to the first major surface, and an edge surface extending between the first major surface and the second major surface. The glass sheet includes a thickness between 0.3 mm and 2 mm. The glass sheet includes a dome or bowl shape.

A light selective transmission type glass 10 according to the present invention includes: a glass substrate 12; and a light selective transmission layer 11 provided on at least one main surface of the glass substrate 12. The glass substrate 12 has an average thermal expansion coefficient .sub.50/100 at 50 C. to 100 C. of 2.70 ppm/ C. to 3.20 ppm/ C., an average thermal expansion coefficient .sub.200/300 at 200 C. to 300 C. of 3.45 ppm/ C. to 3.95 ppm/ C., a value .sub.200/300/.sub.50/100 obtained by dividing the average thermal expansion coefficient .sub.200/300 at 200 C. to 300 C. by the average thermal expansion coefficient .sub.50/100 at 50 C. to 100 C. of 1.20 to 1.30, and a content of an alkali metal oxide being 0% to 0.1%.

A method of treating a ceramic body in a glass making process includes delivering a molten glass to a heated ceramic body, the ceramic body including a ceramic phase and an intergranular glass phase, the molten glass being in contact with a surface of the ceramic body. The method further includes contacting the ceramic body with a first electrode and contacting the molten glass with a second electrode. The method further includes applying an electric field between the first electrode and the second electrode to create an electric potential difference across the ceramic body between the first and second electrodes, the electric potential difference being less than an electrolysis threshold of the ceramic phase and the intergranular glass phase. The intergranular glass phase demixes under driven diffusion in the applied electric field and mobile cations in the intergranular glass phase enrich proximate one of the first and second electrode.

Methods for producing a glass ribbon include drawing a quantity of molten material from a forming vessel into a glass ribbon with the forming vessel positioned within a first portion of a housing located within an upper chamber. The methods further include drawing the glass ribbon along a draw path passing through a second portion of the housing at least partially located within a lower chamber. The methods further include venting gas from an interior of housing through a wall of the second portion of the housing. In one example, the method further includes maintaining a pressure difference between the lower chamber and the upper chamber. In another example, the method includes maintaining a pressure difference between the interior of the housing and the upper chamber.

A method of controlling compaction including obtaining a plurality of sets of process conditions for a plurality of glass ribbons, measuring a compaction value for a glass sheet cut from each glass ribbon of the plurality of glass ribbons, correlating the compaction to the process conditions. The method further includes selecting a predetermined cooling curve including a plurality of cooling rates, modifying the cooling curve by varying cooling rates of the plurality of cooling rates, calculating a predicted compaction value for a glass sheet cut from a glass ribbon drawn using the modified cooling curve, and repeating the modification and predicting until compaction is minimized.

A strengthened glass article (100), such as a substrate for a p-Si based transistors, includes first and second glass cladding layers (104, 106) and a glass core layer (102) disposed therebetween. A coefficient of thermal expansion [CTE] of each cladding layer (104, 106), which can be made of the same glass, is at least 110.sup.7 C..sup.1 less than that of the core layer (102). Each of the core and cladding layers has a strain point less than 700 C. A compaction of the glass article (100) is at most about 20 ppm [see FIG. 1]. A method includes forming a glass article and/or heating a glass article to a first temperature of at least about 400 C. The glass article has a glass core layer (102) and a glass cladding layer (104, 106) adjacent to the core layer. The glass article is maintained at a temperature within a range of from 400 C. to 600 C. for a holding period from 30 to 90 minutes and subsequently cooled to a temperature of at most 50 C. over a cooling period from 30 seconds to 5 minutes. The glass article (100) for heat strengthening may have been produced by the fusion overflow down draw process, e.g. as depicted in FIG. 3.