Glass for chemical tempering, chemically tempered glass, and glass plate for display device

Abstract

To provide glass to be used for chemically tempered glass, of which the strength is less likely to be reduced even when indentations are formed thereon. Glass for chemical tempering, which comprises, as represented by mole percentage based on oxides, from 62 to 68% of SiO 2 , from 6 to 12% of Al 2 O 3 , from 7 to 13% of MgO, from 9 to 17% of Na 2 O, and from 0 to 7% of K 2 O, wherein the difference obtained by subtracting the content of Al 2 O 3 from the total content of Na 2 O and K 2 O is less than 10%, and when ZrO 2 is contained, its content is at most 0.8%. Chemically tempered glass obtained by chemically tempering such glass for chemical tempering. Such chemically tempered glass has a compressive stress layer formed on the glass surface, which has a thickness of at least 30 μm and a surface compressive stress of at least 550 MPa.

What is claimed is: 
     
         1 . Glass for chemical tempering, which comprises, as represented by mole percentage based on oxides, from 62 to 68% of SiO 2 , from 6 to 12% of Al 2 O 3 , from 7 to 13% of MgO, from 9 to 17% of Na 2 O, and from 0 to 7% of K 2 O, wherein the difference obtained by subtracting the content of Al 2 O 3  from the total content of Na 2 O and K 2 O is less than 10%, and when ZrO 2  is contained, its content is at most 0.8%. 
     
     
         2 . The glass for chemical tempering according to  claim 1 , which contains from 64 to 67% of SiO 2 , and from 6 to 7.5% of Al 2 O 3 , wherein the total content of SiO 2  and Al 2 O 3  is from 69 to 73%. 
     
     
         3 . Glass for chemical tempering, which comprises, as represented by mole percentage based on oxides, from 62 to 66% of SiO 2 , from 6 to 12% of Al 2 O 3 , from 7 to 13% of MgO, from 9 to 17% of Na 2 O, and from 0 to 7% of K 2 O, wherein the difference obtained by subtracting the content of Al 2 O 3  from the total content of Na 2 O and K 2 O is less than 10%, and when ZrO 2  is contained, its content is at most 0.8%. 
     
     
         4 . The glass for chemical tempering according to  claim 3 , wherein the total content of SiO 2  and Al 2 O 3  is more than 72%. 
     
     
         5 . The glass for chemical tempering according to  claim 1 , wherein the total content of Na 2 O and K 2 O is from 14 to 22%. 
     
     
         6 . Glass for chemical tempering, which comprises, as represented by mole percentage based on oxides, from 64 to 68% of SiO 2 , from 6 to 11% of Al 2 O 3 , from 7 to 12% of MgO, from 12 to 17% of Na 2 O, and from 0 to 6% of K 2 O, wherein the difference obtained by subtracting the content of Al 2 O 3  from the total content of Na 2 O and K 2 O is less than 10%, and when ZrO 2  is contained, its content is at most 0.8%. 
     
     
         7 . The glass for chemical tempering according to  claim 6 , which contains from 65 to 68% of SiO 2 , from 7 to 10% of Al 2 O 3 , and from 0 to 2.5% of K 2 O, wherein the total content of SiO 2  and Al 2 O 3  is from 73.5 to 76%. 
     
     
         8 . The glass for chemical tempering according to  claim 6 , wherein the content of SiO 2  is at most 66%. 
     
     
         9 . The glass for chemical tempering according to  claim 6 , wherein the total content of Na 2 O and MgO is from 21 to 25%. 
     
     
         10 . The glass for chemical tempering according to  claim 6 , wherein the total content of Na 2 O and K 2 O is at most 18%. 
     
     
         11 . The glass for chemical tempering according to  claim 1 , wherein the total content of Na 2 O, K 2 O and MgO is from 24 to 28%. 
     
     
         12 . The glass for chemical tempering according to  claim 6 , wherein R calculated by the following formula by using the contents of the respective components of SiO 2 , Al 2 O 3 , MgO, CaO, ZrO 2 , Na 2 O and K 2 O is at least 0.66:
   R=0.029×SiO 2 +0.021×Al 2 O 3 +0.016×MgO−0.004×CaO+0.016×ZrO 2 +0.029×Na 2 O+0×K 2 O−2.002
   
     
     
         13 . The glass for chemical tempering according to  claim 1 , wherein the content of K 2 O is at least 0.5%. 
     
     
         14 . The glass for chemical tempering according to  claim 1 , wherein the total content of SiO 2 , Al 2 O 3 , MgO, Na 2 O and K 2 O is at least 98%. 
     
     
         15 . The glass for chemical tempering according to  claim 1 , which has a glass transition point of at least 600° C. 
     
     
         16 . The glass for chemical tempering according to  claim 1 , which has a temperature of at most 1650° C. at which the viscosity becomes to be 10 2  dPa·s. 
     
     
         17 . The glass for chemical tempering according to  claim 1 , which is to be used for obtaining glass, of which a compressive stress layer formed on the glass surface by chemical tempering has a thickness t of at least 30 μm and a surface compressive stress S of at least 550 MPa. 
     
     
         18 . The glass for chemical tempering according to  claim 17 , wherein F1/F0 can be made to be at least 0.9, where F0 is a flexural strength of a chemically tempered glass plate which is obtained by chemically tempering a glass plate made of the glass for chemical tempering and having a thickness of 1 mm and a size of 5 mm×40 mm and which has t of at least 30 μm and S of at least 550 MPa, and F1 is a flexural strength of such a chemically tempered glass plate having a Vickers indenter impressed thereinto with a force of 9.8N. 
     
     
         19 . The glass for chemical tempering according to  claim 17 , wherein F2/F0 can be made to be at least 0.7, where F0 is a flexural strength of a chemically tempered glass plate which is obtained by chemically tempering a glass plate made of the glass for chemical tempering and having a thickness of 1 mm and a size of 5 mm×40 mm and which has t of at least 30 μm and S of at least 550 MPa, and F2 is a flexural strength of such a chemically tempered glass plate having a Vickers indenter impressed thereinto with a force of 19.6N. 
     
     
         20 . The glass for chemical tempering according to  claim 18 , wherein the t is from 45 to 55 μm and the S is from 750 to 850 MPa. 
     
     
         21 . Chemically tempered glass, which is obtained by chemically tempering the glass for chemical tempering as defined in  claim 1 . 
     
     
         22 . The chemically tempered glass according to  claim 21 , of which a compressive stress layer formed on the glass surface has a thickness t of at least 30 μm, and a surface compressive stress S of at least 550 MPa. 
     
     
         23 . A chemically tempered glass plate which is a glass plate made of the chemically tempered glass as defined in  claim 22  and having a thickness of from 0.4 to 1.2 mm, wherein F1/F0 is at least 0.9, where F0 is its flexural strength and F1 is a flexural strength of the glass plate having a Vickers indenter impressed thereinto with a force of 9.8N. 
     
     
         24 . A chemically tempered glass plate which is a glass plate made of the chemically tempered glass as defined in  claim 22  and having a thickness of from 0.4 to 1.2 mm, wherein F2/F0 is at least 0.7, where F0 is its flexural strength and F2 is a flexural strength of the glass plate having a Vickers indenter impressed thereinto with a force of 19.6N. 
     
     
         25 . A glass plate for a display device, which is made of the chemically tempered glass as defined in  claim 21 . 
     
     
         26 . A glass plate for a display device, which is made of the chemically tempered glass plate as defined in  claim 23 . 
     
     
         27 . A display device, which has a cover glass comprising the glass plate for a display device as defined in  claim 25 . 
     
     
         28 . A mobile device, which has a cover glass comprising the glass plate for a display device as defined in  claim 25 . 
     
     
         29 . A touch panel, which has a cover glass comprising the glass plate for a display device as defined in  claim 25 . 
     
     
         30 . A flat screen television with a size of at least 20 inches, which has a cover glass comprising the glass plate for a display device as defined in  claim 25 .