Central Glass Company, Limited

Tadashi Muramoto

Shinichi Aratani

Tatsuya Tsuzuki

Naoki Mitamura

Yoshio Mohri

Takashi Hiroishi

Kinzi Sano

Masato Tao

Yu Matsuda

Koichi Huruya

The present invention aims to provide a chemically strengthened glass plate which has a good yield in a cutting process of the chemically strengthened glass plate and has sufficient strength. The chemically strengthened glass plate has a surface compressive stress of not less than 600 MPa at a surface of the chemically strengthened glass plate, and a compressive stress layer containing two types of stress patterns A and B. The stress pattern A is a stress pattern of a surface portion of the glass plate, and the stress pattern B is a stress pattern of an inside of the glass plate. The stress patterns satisfy the formula S&#x3e;Swhere Srepresents a slope of the stress pattern A and Srepresents a slope of the stress pattern B when the stress patterns A and B are each approximated by a linear function.

Chemically strengthened glass plate and method for manufacturing same

The invention relates to a lithium-sodium-aluminosilicate glass composition. This glass composition has a softening point of 700&deg; C. or lower; a first temperature (1450&deg; C. or lower) at which the glass composition exhibits a viscosity of 10 poises; a second temperature (1000&deg; C. or lower) at which the glass exhibits a viscosity of 10 poises; and a mean thermal expansion coefficient between 30&deg; C. and a glass transition temperature of the glass composition. This coefficient is within a range of from 90&times;10 /&deg; C. to 130&times;10 /&deg; C. The glass composition can be easily formed into a precursor of a glass article by pressing. It is possible to obtain a glass article that is chemically strengthened from the precursor by conducing alkali ion exchange.

Glass composition and ion exchange strengthened glass article produced from same

The invention relates to a method of tempering a glass sheet by first suitably heating the glass sheet and quenching the heated glass sheet by directing jets of air onto both surfaces of the glass sheet from two sets of nozzles respectively protruding from oppositely disposed two air chambers. At the start of quenching, each air chamber is suddenly allowed to communicate with a source of compressed air kept at a predetermined first pressure in the range from 2 to 8 kg/cm.sup.2 (gauge pressure) such that a rapid drop from the first pressure to a predetermined second pressure in the range from 0.05 to 0.5 kg/cm.sup.2 (gauge pressure) takes place as the compressed air expands into the air chamber and such that substantially the whole length of the air chamber and the nozzles serves as a sort of shock wave tube. Consequently, the air jets arriving at the glass sheet surfaces at the initial stage of quenching are very high in kinetic energy and heat dissipating power. By this method even glass sheets thinner than 3 mm can be tempered so as to meet the current regulations on tempered glass sheets for use as automobile side or rear windows.

Method of tempering glass sheet by air quenching

In toughening a glass sheet, e.g. for use as an automobile window, by heating it to a temperature above the strain point and quenching the heated glass sheet by blowing a cooling medium such as compressed air against both sides of the glass sheet from two opposite sets of nozzles, the cooling medium is caused to impinge on each side of the glass sheet in such a pattern that the glass sheet is more efficiently quenched and consequently more highly toughened in a generally circular central region and a plurality of generally annular regions, which are substantially concentrical about the center of the glass sheet and radially spaced from one another, than in the remaining regions. This is effective in preventing the presence of impermissibly elongated particles when the glass sheet is fractured and also in lessening the difference between the maximum and minimum numbers of particles in unit areas of the fractured glass sheet. For example, the desired pattern can be produced by arranging each set of the nozzles on a plurality of concentrical circumferences. Every nozzle may be directed perpendicular to the glass sheet or, rather preferably, tangentially inclined from the direction perpendicular to the glass sheet.

Method of toughening glass sheet by quenching

A glass composition particularly useful for producing alkali-resistant glass fibers, containing, by weight, from 53 to 63% SiO.sub.2, from 21 to 23% ZrO.sub.2 and from 10 to 21% Na.sub.2 O.

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Mie, Japan

Tadashi Muramoto