Ion exchange strengthened glass containing P2 O5

Claim 1

A glass essentially transparent to visible light and capable of being strengthened by ion exchange with potassium ions, comprising by weight on the oxide basis: 34 to 61 percent SiO 2 12 to 20 percent Na 2 O 2 to 9 percent K 2 O 17 to 23 percent (Na 2 O + K 2 O) 2 to 15 percent Al 2 O 3 0to 10 percent ZrO 2 9 to 23 percent (Al 2 O 3 + ZrO 2 ) 2 to 20 percent P 2 O 5 0 to 8 percent ZnO 0 to 6 percent MgO 0 to 5 percent TiO 2 2 to 9 percent (ZnO + MgO + TiO 2 ) 0 to 0.1 percent Li 2 O wherein said constituents comprise at least 90 percent by weight of the glass and are proportioned relative to one another so as to provide the glass with a viscosity of 100 poises at a temperature less than 2800° F. (1538° C.)

Claim 12

A method of strengthening a transparent glass article comprising the steps of: a. contacting a source of potassium ions with the surface of a glass article comprising by weight on the oxide basis: 34 to 61 percent SiO 2 12 to 20 percent Na 2 O 2 to 9 percent K 2 O 17 to 23 percent (Na 2 O + K 2 O) 2 to 15 percent Al 2 O 3 0 to 10 percent ZrO 2 9 to 23 percent (Al 2 O 3 + ZrO 2 ) 2 to 20 percent P 2 O 5 0 to 8 percent ZnO 0 to 6 percent MgO 0 to 5 percent TiO 2 2 to 9 percent (ZnO + MgO + TiO 2 ) 0 to 0.1 percent Li 2 O said constituents comprising at least 90 percent by weight of the glass article and proportioned relative to one another so as to provide a glass having a viscosity of 100 poises at a temperature less than 2800° F. (1538° C.); b. heating said source of potassium ions while in contact with the glass to a temperature at which potassium ions from said source replace sodium ions in the glass, but essentially below the strain point of the glass, thereby creating a zone of compression at the surface of the glass which extends at least 5 microns into the glass; and c. removing the glass from contact with the potassium ion source.

Claim 13

A method of strengthening a transparent glass article comprising the steps of: a. contacting a source of potassium ions with the surface of a glass article comprising by weight on the oxide basis: 34 to 61 percent SiO 2 12 to 20 percent Na 2 O 2 to 9 percent K 2 O 17 to 23 percent (Na 2 O + K 2 O) 2 to 15 percent Al 2 O 3 0 to 10 percent ZrO 2 9 to 23 percent (Al 2 O 3 + ZrO 2 ) 2 to 20 percent P 2 O 5 0 to 8 percent ZnO 0 to 6 percent MgO 0 to 5 percent TiO 2 2 to 9 percent (ZnO + MgO + TiO 2 ) 0 to 0.1 percent Li 2 O said constituents comprising at least 90 percent by weight of the glass article and proportioned relative to one another so as to provide a glass having a viscosity of 100 poises at a temperature less than 2800° F. (1538° C.); b. heating said source of potassium ions while in contact with the glass to a temperature at which potassium ions from said source replace sodium ions in the glass, but essentially below the strain point of the glass, thereby creating a zone of compression at the surface of the glass which extends at least 5 microns into the glass; and c. removing the glass from contact with the potassium ion source.