Strengthened glass articles and methods of making

Abstract

A strengthened glass article having a central tension that is below a threshold value above which the glass exhibits frangible behavior. The central tension varies non-linearly with the thickness of the glass. The glass article may be used as cover plates or windows for portable or mobile electronic devices such as cellular phones, music players, information terminal (IT) devices, including laptop computers, and the like.

1 . A strengthened glass article, the strengthened glass article having a thickness t≦0.75 mm and comprising:
 an outer region; 
 an inner region, wherein the inner region is under a central tension CT, and wherein CT (MPa)>−15.7 (MPa/mm)·t (mm)+52.5 (MPa), 
 wherein when the strengthened glass article is broken by a point impact, the strengthened glass article exhibits at least one of fragment size n 1  (%≦1 mm) of 0%≦n 1 ≦5%, crack branching n 3  of 0≦n 3 ≦5, or combinations thereof. 
 
     
     
         2 . The strengthened glass article of  claim 1 , wherein when the strengthened glass is broken by a point impact, the strengthened glass article further exhibits at least one of fragment density n 2  (fragments/cm 2 ) of 0 fragments/cm 2 ≦n 2 ≦3 fragments/cm 2 , ejection n 4  (%≧5 cm) of 0%≦ 4 ≦2%, or combinations thereof. 
     
     
         3 . The strengthened glass article of  claim 1 , wherein the strengthened glass article has a frangibility index of less than 3. 
     
     
         4 . The strengthened glass article of  claim 1 , wherein the strengthened glass article has a frangibility index of less than 2. 
     
     
         5 . The strengthened glass article of  claim 2 , wherein the strengthened glass article exhibits at least one of fragment size n 1  (%≦1 mm) of 0%, fragment density n 2  (fragments/cm 2 ) of ≦1 fragments/cm 2 , crack branching n 3  of ≦2, ejection n 4  (%≧5 cm) of 0%, or combinations thereof. 
     
     
         6 . The strengthened glass article of  claim 5 , wherein the strengthened glass article has a frangibility index of less than 2. 
     
     
         7 . The strengthened glass article of  claim 1 , wherein the strengthened glass article is non-frangible. 
     
     
         8 . The strengthened glass article of  claim 1 , wherein the strengthened glass article comprises an alkali aluminosilicate glass. 
     
     
         9 . The strengthened glass article of  claim 8 , wherein the alkali aluminosilicate glass comprises: 60-70 mol % SiO 2 ; 6-14 mol % Al 2 O 3 ; 0-15 mol % B 2 O 3 ; 0-15 mol % Li 2 O; 0-20 mol % Na 2 O; 0-10 mol % K 2 O; 0-10 mol % CaO; 0-5 mol % ZrO 2 ; 0-1 mol % SnO 2 ; 0-1 mol % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; wherein 12 mol %≦Li 2 O+Na 2 O+K 2 O≦20 mol % and 0 mol %≦MgO+CaO≦10 mol %. 
     
     
         10 . A strengthened glass article, the strengthened glass article having a thickness t≦0.75 mm and comprising:
 an outer region; 
 an inner region, wherein the inner region is under a central tension CT, and wherein CT (MPa)>−15.7 (MPa/mm)·t (mm)+52.5 (MPa), 
 wherein when the strengthened glass article is broken by a point impact, the strengthened glass article exhibits at least one of fragment size n 1  (%≦1 mm) of 0%≦n 1 ≦5%, fragment density n 2  (fragments/cm 2 ) of 0 fragments/cm 2 ≦n 2 ≦3 fragments/cm 2 , crack branching n 3  of 0≦n 3 ≦5, ejection n 4  (%≧5 cm) of 0%≦n 4 ≦2%, or combinations thereof. 
 
     
     
         11 . The strengthened glass article of  claim 10 , wherein the strengthened glass article has a frangibility index of less than 3. 
     
     
         12 . The strengthened glass article of  claim 10 , wherein the strengthened glass article exhibits at least one of fragment size n 1  (%≦1 mm) of 0%, fragment density n 2  (fragments/cm 2 ) of ≦1 fragments/cm 2 , crack branching n 3  of ≦2, ejection n 4  (%>5 cm) of 0%, or combinations thereof. 
     
     
         13 . The strengthened glass article of  claim 10 , wherein the strengthened glass article is non-frangible. 
     
     
         14 . The strengthened glass article of  claim 10 , wherein the strengthened glass article comprises an alkali aluminosilicate glass. 
     
     
         15 . The strengthened glass article of  claim 14 , wherein the alkali aluminosilicate glass comprises: 60-70 mol % SiO 2 ; 6-14 mol % Al 2 O 3 ; 0-15 mol % B 2 O 3 ; 0-15 mol % Li 2 O; 0-20 mol % Na 2 O; 0-10 mol % K 2 O; 0-10 mol % CaO; 0-5 mol % ZrO 2 ; 0-1 mol % SnO 2 ; 0-1 mol % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; wherein 12 mol %≦Li 2 O+Na 2 O+K 2 O≦20 mol % and 0 mol %≦MgO+CaO≦10 mol %.