Lithium-aluminosilicate glass with short glazing times

Abstract

A lithium-aluminosilicate glass or a corresponding glass ceramic that has a content of 0-0.4 SnO 2 , 1.3-2.7% by weight of ΣSnO 2 +TiO 2 , 1.3-2.5% by weight of ZrO 2 , 3.65-4.3% by weight of ΣZrO 2 +0.87 (TiO 2 +SnO 2 ), ≦0.04% by weight of Fe 2 O 3 , 50-4000 ppm of Nd 2 O 3 and 0-50 ppm of CoO is described. The glass or the glass ceramic is color-neutral, has a turbidity of less than 1% HAZE and a high light transmission. The glazing time for conversion of the glass into glass ceramic is especially short with less than 2.5 hours.

1 . Lithium-aluminosilicate glass, which can be converted with glazing times of under 2.5 hours into a transparent glass ceramic with high-quartz mixed crystals as the prevailing crystal phase, which has a turbidity of less than 1% according to ASTM D 1003 and has a neutral color shade, characterized by a content in % by weight based on oxide of: 
     
       
         
               
               
             
                   
               
                   0-0.4 
                 SnO 2   
               
                 1.3-2.7 
                 ΣSnO 2  + TiO 2   
               
                 1.3-2.5 
                 ZrO 2   
               
                 3.65-4.3  
                 ΣZrO 2  + 0.87 (TiO 2 + SnO 2 ) 
               
                 ≦0.04 
                 Fe 2 O 3   
               
                 0.005-0.4  
                 Nd 2 O 3   
               
                    0-0.005 
                 CoO 
               
                   
               
           
              
             
             
              
              
              
              
              
              
              
              
             
          
         
       
     
   
   
       2 . Lithium-aluminosilicate glass according to  claim 1 , characterized by a content (in % by weight based on oxide) of: 
     
       
         
               
               
               
             
                   
                   
               
                   
                 Li 2 O 
                 3.0-4.5   
               
                   
                 Na 2 O 
                 0-1.5 
               
                   
                 K 2 O 
                 0-1.5 
               
                   
                 ΣNa 2 O + K 2 O 
                 0.2-2.0   
               
                   
                 MgO 
                 0-2.0 
               
                   
                 CaO 
                 0-1.5 
               
                   
                 SrO 
                 0-1.5 
               
                   
                 BaO 
                 0-2.5 
               
                   
                 ZnO 
                 0-2.5 
               
                   
                 B 2 O 3   
                 0-1.0 
               
                   
                 Al 2 O 3   
                 19-25   
               
                   
                 SiO 2   
                 55-69   
               
                   
                 TiO 2   
                 1.4-2.7   
               
                   
                 ZrO 2   
                 1.3-2.5   
               
                   
                 SnO 2   
                 0-0.4 
               
                   
                 ΣSnO 2  + TiO 2   
                 <2.7 
               
                   
                 P 2 O 5   
                 0-3.0 
               
                   
                 Nd 2 O 3   
                 0.01-0.4   
               
                   
                 CoO 
                  0-0.004 
               
                   
                   
               
           
              
             
             
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
             
          
         
       
     
     optionally with additions of chemical refining agents such as As 2 O 3 , Sb 2 O 3 , and CeO 2  and refining additives such as sulfate, chloride and fluoride compounds in total contents of up to 2.0% by weight. 
   
   
       3 . Lithium-aluminosilicate glass according to  claim 2 , characterized by a content (in % by weight based on oxide) of: 
     
       
         
               
               
               
             
                   
                   
               
                   
                 Li 2 O 
                 3.2-4.3 
               
                   
                 Na 2 O 
                 0.2-1.0 
               
                   
                 K 2 O 
                   0-0.8 
               
                   
                 ΣNa 2 O + K 2 O 
                 0.3-1.5 
               
                   
                 MgO 
                 0.1-1.5 
               
                   
                 CaO 
                   0-1.0 
               
                   
                 SrO 
                   0-1.0 
               
                   
                 BaO 
                   0-2.5 
               
                   
                 ZnO 
                   0-2.0 
               
                   
                 Al 2 O 3   
                 19-24 
               
                   
                 SiO 2   
                 60-68 
               
                   
                 TiO 2   
                 1.4-2.7 
               
                   
                 ZrO 2   
                 1.3-2.2 
               
                   
                 SnO 2   
                   0-0.3 
               
                   
                 ΣSnO 2  + TiO 2   
                 <2.7 
               
                   
                 P 2 O 5   
                   0-1.5 
               
                   
                 Nd 2 O 3   
                 0.02-0.3  
               
                   
                 CoO 
                    0-0.003 
               
                   
                   
               
           
              
             
             
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
             
          
         
       
     
     optionally with the additions of chemical refining agents such as As 2 O 3 , Sb 2 O 3 , and CeO 2  and refining additives such as sulfate compounds, chloride compounds, and fluoride compounds in total amounts of up to 1.5% by weight. 
   
   
       4 . Lithium-aluminosilicate glass according to  claim 1 , characterized by an MgO content of <0.8, preferably <0.6% by weight. 
   
   
       5 . Glass ceramic, converted from a lithium-aluminosilicate glass with a composition according to  claim 1 . 
   
   
       6 . Transparent glass ceramic converted from a lithium-aluminosilicate glass with a composition according to  claim 1 , with a content of Nd 2 O 3 <2000 ppm, CoO<20 ppm and a thermal expansion coefficient α 20/700  of 0±0.5·10 −6 /K, preferably 0±0.3·10 −6 /K, a light transmission with a thickness of 4 mm of greater than 80% and a variegation of colors in the CIELAB color system C*<3.5. 
   
   
       7 . Use of the transparent glass ceramic, converted from a lithium-aluminosilicate glass with a composition according to  claim 1 , as fire protection glass, fireplace door windows, oven door windows, cooking surfaces with bottom coating and covers in the lighting sector.