Transparent glass ceramic plate that has an opaque, colored bottom coating over the entire surface or over part of the surface

Abstract

A transparent, colorless lithium-aluminosilicate glass ceramic plate with high-quartz mixed crystals as the prevailing crystal phase, which is provided on one side with an opaque, colored, temperature-stable coating over the entire surface or over the entire surface to a large extent, is described, which has a content of Nd 2 O 3 of 40 to 4000 ppm, a Yellowness Index of less than 10% with a 4 mm glass (ceramic) layer thickness, and a variegation of colors of the glass or the glass ceramic in the CIELAB color system of C* of less than 5. The glass ceramic plate preferably has a composition (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 1-3, ZrO 2 1-2.5, SnO 2 0-0.4, ΣSnO 2 +TiO 2 <3, P 2 O 5 0-3.0, Nd 2 O 3 0.01-0.4, CoO 0.0-0.004

1 . Transparent, colorless lithium-aluminosilicate glass ceramic plate with high-quartz mixed crystals as the prevailing crystal phase, which is provided on one side with an opaque, colored, temperature-stable coating over the entire surface or over the entire surface to a large extent, characterized by a content of Nd 2 O 3  of 40 to 4000 ppm, a Yellowness Index of less than 10% with a 4 mm thickness, and a variegation of colors of the glass ceramic in the CIELAB color system of C* of less than 5.  
   
   
       2 . Glass ceramic plate according to  claim 1 , characterized by an additional content of 0-50 ppm of CoO.  
   
   
       3 . Glass ceramic plate according to  claim 1 , characterized by a composition (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   
                 1-3   
               
                   
                 ZrO 2   
                 1-2.5 
               
                   
                 SnO 2   
                 0-0.4 
               
                   
                 ΣSnO 2  + TiO 2   
                 <3 
               
                   
                 P 2 O 5   
                 0-3.0 
               
                   
                 Nd 2 O 3   
                 0.01-0.4   
               
                   
                 CoO 
                  0.0-0.004 
               
                   
                   
               
                   
                   
               
           
              
              
             
             
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
             
          
         
       
     
     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 contents of up to 2.0% by weight.  
   
   
       4 . Glass ceramic plate according to  claim 3 , 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   
                 1.0-2.7 
               
                   
                 ZrO 2   
                 1.2-2.2 
               
                   
                 SnO 2   
                   0-0.3 
               
                   
                 ΣSnO 2  + TiO 2   
                 <2.7 
               
                   
                 P 2 O 5   
                   0-3.0 
               
                   
                 Nd 2 O 3   
                 0.02-0.3  
               
                   
                 CoO 
                  0.0-0.003 
               
                   
                   
               
                   
                   
               
           
              
              
             
             
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
              
             
          
         
       
     
     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.  
   
   
       5 . Glass ceramic plate according to  claim 3 , characterized in that the content of ZrO 2 +0.87 (TiO 2 +SnO 2 ) is 3.65 to 4.3% by weight.  
   
   
       6 . Glass ceramic plate according to  claim 1 , characterized by a content of less than 2.5% by weight of TiO 2 , less than 2000 ppm of Nd 2 O 3 , less than 400 ppm, preferably less than 210 ppm of Fe 2 O 3 , a light transmittance of more than 80%, in particular more than 85%, and a Yellowness Index of less than 7, in each case with a 4 mm layer thickness as well as a variegation of colors of C* of less than 3.5 in the CIELAB color system.