Glass for chemical tempering and glass plate for display device

Abstract

To provide glass to be used for chemically tempered glass which is hardly broken even when flawed. Glass for chemical tempering, which comprises, as represented by mole percentage based on the following oxides, from 65 to 85% of SiO 2 , from 3 to 15% of Al 2 O 3 , from 5 to 15% of Na 2 O, from 0 and less than 2% of K 2 O, from 0 to 15% of MgO and from 0 to 1% of ZrO 2 , and has a total content Si0 2 +Al 2 O 3 of SiO 2 and Al 2 O 3 of at most 88%.

1 . A glass, comprising, as represented by mole percentage based on the following oxides:
 from 68 to 85% of SiO 2 ;   from 3 to 15% of Al 2 O 3 ;   from 5 to 15% of Na 2 O;   from 0 to 0.8% of K 2 O;   from 5 to 15% of MgO; and   from 0 to 1% of ZrO 2 ,   wherein a total content of SiO 2  and Al 2 O 3 , SiO 2 +Al 2 O 3 , is at most 88%.   
     
     
         2 . The glass of  claim 1 , comprising:
 from 68 to 80% of SiO 2 ; and   from 4 to 10% of Al 2 O 3 ,   wherein a total content SiO 2 +Al 2 O 3  is at most 85%.   
     
     
         3 . The glass of  claim 1 , which contains no CaO, or has a CaO content of less than 1% if contained. 
     
     
         4 . The glass of  claim 1 , comprising:
 at most 77% of SiO 2 ; and   at least 8% of Na 2 O;   wherein a total content SiO 2 +Al 2 O 3  is at most 85%, a content of CaO of less than 1% if contained, and wherein the glass contains no K 2 O.   
     
     
         5 . The glass of  claim 1 , wherein a total content SiO 2 +Al 2 O 3  is at least 75%. 
     
     
         6 . The glass of  claim 1 , comprising at least 4.5% of Al 2 O 3 . 
     
     
         7 . The glass of  claim 1 , comprising:
 from 70 to 75% of SiO 2 ;   at least 5% of Al 2 O 3 ;   at least 8% of Na 2 O; and   from 5 to 12% of MgO,   wherein a total content SiO 2 +Al 2 O 3  is from 77 to 83%.   
     
     
         8 . The glass of  claim 1 , comprising at most 6% of Al 2 O 3 . 
     
     
         9 . The glass of  claim 1 , comprising at least 8% of MgO. 
     
     
         10 . The glass of  claim 1 , wherein a total content of CaO, SrO, BaO, and ZrO 2  is less than 1.5% if at least one of these four components is contained. 
     
     
         11 . The glass of  claim 1 , wherein a total content of SiO 2 , Al 2 O 3 , Na 2 O, and MgO is at least 98%. 
     
     
         12 . The glass of  claim 1 , wherein when it is formed into a glass plate having a thickness of 1 mm and chemically tempered, and when a force of 98 N is applied to its mirror-polished surface by means of a Vickers indenter, the probability that the chemically tempered glass plate is broken is at most 10%. 
     
     
         13 . The glass of  claim 1 , wherein when it is formed into a glass plate having a thickness of 1 mm and chemically tempered, and when a force of 196 N is applied to its mirror-polished surface by means of a Knoop indenter, the probability that the chemically tempered glass plate is broken is at most 10%. 
     
     
         14 . The glass of  claim 1 , wherein Δ represented by the following formula is at most 0.21:
   Δ=(S 400 -S 450 )/S 400  
 
 
       wherein S 400  is a surface compressive stress obtained when the glass is formed into a glass plate having a thickness of 1 mm and immersed in KNO 3  at 400° C. for 6 hours, and S 450  is a surface compressive stress obtained when the glass is formed into a glass plate having a thickness of 1 mm and immersed in KNO 3  at 450° C. for 6 hours. 
     
     
         15 . A chemically tempered glass obtained by chemically tempering the glass of  claim 1 . 
     
     
         16 . The chemically tempered glass of  claim 15 , having a compressive stress layer thickness of at least 10 μm, and a surface compressive stress of at least 400 MPa. 
     
     
         17 . A glass plate obtained by chemically tempering a glass plate comprising the glass of  claim 1 . 
     
     
         18 . A display device, comprising a cover glass comprising the glass plate of  claim 17 . 
     
     
         19 . The display device of  claim 18 , which is a mobile device, a touch panel, or a flat screen television having a size of at least 20 inches.