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≦0.5 mm comprising:
 an alkali aluminosilicate glass having less than 50 ppm As 2 O 3    
 an outer region having a depth of layer of at least 30 μm and a compressive stress of at least 600 MPa, 
 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) and 
 wherein the strengthened glass article is substantially non-frangible when subjected to a point impact sufficient to break the strengthened glass article 
 
     
     
         2 . The strengthened glass article of  claim 1  has a frangibility index of less than 3. 
     
     
         3 . The strengthened glass article of  claim 1 , wherein the strengthened glass article has a thickness t<0.5 mm. 
     
     
         4 . The strengthened glass article of  claim 1 , wherein the strengthened glass article has a thickness t of 0.5 mm. 
     
     
         5 . The strengthened glass article of  claim 2 , wherein when the strengthened glass article is broken by the 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 and ejection n 4  (%≧5 cm) of 0%≦n 4 ≦2%, or combinations thereof. 
     
     
         6 . The strengthened glass article according to  claim 1 , 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 %. 
     
     
         7 . The strengthened glass article of  claim 6 , wherein the alkali aluminosilicate glass further comprises up to 8 mol % MgO. 
     
     
         8 . The strengthened glass article of  claim 6 , wherein 0 mol %<SnO 2 ≦1 mol %. 
     
     
         9 . The strengthened glass article of  claim 1 , wherein t is between 0.3 mm and 0.5 and CT is between about 75.0 and about 94.8 MPa. 
     
     
         10 . The strengthened glass article of  claim 3 , wherein the thickness of the strengthened glass article is 0.3≦t<0.5 mm. 
     
     
         11 . The strengthened glass article of  claim 10  has a frangibility index of less than 3. 
     
     
         12 . The strengthened glass article of  claim 11 , wherein when the strengthened glass article is broken by the 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 and ejection n 4  (%≧5 cm) of 0%≦n 4 ≦2%, or combinations thereof. 
     
     
         13 . The strengthened glass article according to  claim 10 , wherein the alkali aluminosilicate glass comprises: 60-70 mol % SiO2; 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 %. 
     
     
         14 . The strengthened glass article of  claim 13 , wherein the alkali aluminosilicate glass further comprises up to 8 mol % MgO. 
     
     
         15 . The strengthened glass article of  claim 1 , wherein the alkali aluminosilicate glass is substantially free of lithium. 
     
     
         16 . A strengthened glass article, the strengthened glass article having a thickness t≦0.5 mm comprising:
 an alkali aluminosilicate glass having less than 50 ppm As 2 O 3    
 an outer region having a depth of layer of at least 30 μm and a compressive stress of at least 600 MPa, 
 an inner region, wherein the inner region is under a central tension CT, and wherein −15.7(MPa/mm)·t(mm)+52.5(MPa)≦CT(MPa)≦−38.7 (MPa/mm)·ln(t)(mm)+48.2 (MPa). 
 wherein the strengthened glass article is substantially non-frangible when subjected to a point impact sufficient to break the strengthened glass article 
 
     
     
         17 . The strengthened glass article of  claim 16  has a frangibility index of less than 3. 
     
     
         18 . The strengthened glass article of  claim 16 , wherein the strengthened glass article has a thickness t<0.5 mm. 
     
     
         19 . The strengthened glass article of  claim 16 , wherein the strengthened glass article has a thickness t of 0.5 mm. 
     
     
         20 . The strengthened glass article of  claim 17 , wherein when the strengthened glass article is broken by the 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 and ejection n 4  (%≧5 cm) of 0%≦n 4 ≦2%, or combinations thereof. 
     
     
         21 . The strengthened glass article according to  claim 16 , 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 %. 
     
     
         22 . The strengthened glass article of  claim 21 , wherein the alkali aluminosilicate glass further comprises up to 8 mol % MgO. 
     
     
         23 . The strengthened glass article of  claim 21 , wherein 0 mol %<SnO 2 ≦1 mol %. 
     
     
         24 . The strengthened glass article of  claim 16 , wherein t is between 0.3 mm and 0.5 and CT is between about 75.0 and about 94.8 MPa. 
     
     
         25 . The strengthened glass article of  claim 18 , wherein the thickness of the strengthened glass article is 0.3≦t<0.5 mm. 
     
     
         26 . The strengthened glass article of  claim 25  has a frangibility index of less than 3. 
     
     
         27 . The strengthened glass article of  claim 26 , wherein when the strengthened glass article is broken by the 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 and ejection n 4  (%≧5 cm) of 0%≦n 4 ≦2%, or combinations thereof. 
     
     
         28 . The strengthened glass article according to  claim 10 , wherein the alkali aluminosilicate glass comprises: 60-70 mol % SiO2; 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 %. 
     
     
         29 . The strengthened glass article of  claim 28 , wherein the alkali aluminosilicate glass further comprises up to 8 mol % MgO. 
     
     
         30 . The strengthened glass article of  claim 16 , wherein the alkali aluminosilicate glass is substantially free of lithium.