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 method and apparatus for manufacturing a glass article includes flowing a glass ribbon through a housing having first and second side walls. The first and second side walls extend between the glass ribbon and a cooling mechanism and at least one of the side walls has at least one closeable opening, such that a greater amount of heat is transferred from the glass ribbon when the closeable opening is open than when the closeable opening is closed.

A method and apparatus for manufacturing a glass article includes flowing a glass ribbon through a housing having first and second side walls. The first and second side walls extend between the glass ribbon and a cooling mechanism and at least one of the side walls has at least one closeable opening, such that a greater amount of heat is transferred from the glass ribbon when the closeable opening is open than when the closeable opening is closed.

A method for manufacturing a glass substrate having a strain point of 680° C. or higher, the method includes: a step of melting a glass raw material; and a step of forming a molten glass, in which the forming step includes a step of cooling the molten glass such that a cooling time in a temperature range from an annealing point of the glass substrate to 500° C. is 35 seconds or more, and in a case where a cooling profile indicating a temperature change with respect to the cooling time is linearly approximated by a least-squares method in the temperature range from the annealing point of the glass substrate to 500° C., a coefficient of determination R.sup.2 in the least-squares method is 0.7 or more.

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 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 1×10.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.

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 1×10.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.

Provided is a glass ribbon manufacturing apparatus in which at least one of support rollers configured to support both sides of a glass ribbon (G) in a width direction in an annealing region and a cooling region is a shape stabilization roller configured to stabilize a shape of the glass ribbon (G) curved in the width direction. The shape stabilization roller includes a first roller (11) arranged on one surface side of the glass ribbon (G) and a second roller (12) arranged on another surface side of the glass ribbon (G). Inner end portions (11c) of rollers (11a) of the first roller (11) are all positioned on an outer side, in the width direction, of outer end portions (12c) of rollers (12a) of the corresponding second roller (12) in the width direction.

Provided is a glass ribbon manufacturing apparatus in which at least one of support rollers configured to support both sides of a glass ribbon (G) in a width direction in an annealing region and a cooling region is a shape stabilization roller configured to stabilize a shape of the glass ribbon (G) curved in the width direction. The shape stabilization roller includes a first roller (11) arranged on one surface side of the glass ribbon (G) and a second roller (12) arranged on another surface side of the glass ribbon (G). Inner end portions (11c) of rollers (11a) of the first roller (11) are all positioned on an outer side, in the width direction, of outer end portions (12c) of rollers (12a) of the corresponding second roller (12) in the width direction.

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.