Glasses having improved toughness and scratch resistance

Abstract

A silicate glass that is tough and scratch resistant. The toughness is increased by minimizing the number of non-bridging oxygen atoms in the glass. In one embodiment, the silicate glass is an aluminoborosilicate glass in which −15 mol %←(R2O+R′O—Al2O3—ZrO2)—B2O3≤4 mol %, where R is one of Li, Na, K, Rb, and Cs, and R′ is one of Mg, Ca, Sr, and Ba.

1 . A silicate glass, the silicate glass being ion exchangeable and comprising:
 62-70 mol % SiO2;   >0-18 mol % Al2O3;   0 mol % B2O3;   0-15 mol % Li2O;   6-20 mol % Na2O;   0-18 mol % K2O;   >0-17 mol % MgO;   >0-2 mol % ZrO2; and   SnO2, wherein:   16 mol %≤Al2O3+B2O3+ZrO2≤29 mol %;   14 mol %≤R2O+R′O≤25 mol %; and   −15 mol %≤(R2O+R′O—Al2O3-ZrO2)≤4 mol %, where R is at least one of Li, Na, K, Rb, and Cs, and R′ is at least one of Mg, Ca, Sr, and Ba.   
     
     
         2 . The silicate glass according to  claim 1 , wherein R2O (mol %) is greater than Al2O3 (mol %). 
     
     
         3 . The silicate glass according to  claim 1 , wherein the glass is free of Li2O. 
     
     
         4 . The silicate glass according to  claim 1 , wherein −5 mol %≤(R2O+R′O—Al2O3-ZrO2)≤4 mol %. 
     
     
         5 . The silicate glass according to  claim 1 , wherein the silicate glass comprises less than 5 mol % of at least one of ZnO, Sb2O3, As2O3, La2O3, Y2O3, and Fe2O3. 
     
     
         6 . The silicate glass according to  claim 1 , wherein the silicate glass comprises >0-5 mol % of at least one of ZnO, Sb2O3, As2O3, La2O3, Y2O3, and Fe2O3. 
     
     
         7 . The silicate glass according to  claim 1 , wherein the silicate glass comprises 0-18 mol % CaO. 
     
     
         8 . The silicate glass according to  claim 1 , wherein the silicate glass has a toughness in a range from 0.7 MPa m0.5 up to 1.2 MPa m0.5. 
     
     
         9 . The silicate glass according to  claim 8 , wherein the silicate glass has a brittleness of less than 8.5 μm-0.5. 
     
     
         10 . The silicate glass according to  claim 1 , wherein the silicate glass is ion exchanged and has a surface compressive stress of at least 200 MPa and a surface compressive layer, the surface compressive layer having a depth of at least 30 μm. 
     
     
         11 . The silicate glass according to  claim 1 , wherein the silicate glass has a liquidus viscosity of at least 100 kpoise. 
     
     
         12 . The silicate glass according to  claim 1 , wherein the silicate glass is substantially free of at least one of antimony and arsenic. 
     
     
         13 . The silicate glass according to  claim 1 , wherein the silicate glass forms a cover plate for a mobile electronic device, wherein the cover plate has a thickness in a range from 0.3 mm up to 1.5 mm. 
     
     
         14 . An electronic device comprising a cover plate comprising the silicate glass of  claim 1 . 
     
     
         15 . A silicate glass, the silicate glass being ion exchangeable and comprising:
 62-70 mol % SiO2;   >0-18 mol % Al2O3;   0 mol % B2O3;   0-15 mol % Li2O;   6-20 mol % Na2O;   0-18 mol % K2O;   >0-17 mol % MgO;   >0-2 ZrO2; and   SnO2, wherein:   −15 mol %≤(R2O+R′O—Al2O3-ZrO2)≤4 mol %, where R is at least one of Li, Na, K, Rb, and Cs, and R′ is at least one of Mg, Ca, Sr, and Ba;   the silicate glass has a toughness in a range from 0.7 MPa m0.5 up to 1.2 MPa m0.5; and   the silicate glass has a brittleness of less than 8.5 μm-0.5.   
     
     
         16 . The silicate glass according to  claim 15 , wherein R2O (mol %) is greater than Al2O3 (mol %). 
     
     
         17 . The silicate glass according to  claim 15 , wherein the glass is free of Li2O. 
     
     
         18 . The silicate glass according to  claim 15 , wherein 16 mol %≤Al2O3+B2O3+ZrO2≤29 mol %. 
     
     
         19 . The silicate glass according to  claim 15 , wherein 14 mol %≤R2O+R′O≤25 mol %. 
     
     
         20 . The silicate glass according to  claim 15 , wherein the silicate glass forms a cover plate for a mobile electronic device, wherein the cover plate has a thickness in a range from 0.3 mm up to 1.5 mm.