Glass ceramic or glass cook top with an IR-permeable undercoat

Abstract

The cook top has a transparent, colorless glass ceramic or glass panel providing a cooking surface, which is made from pre-stressed special glass, and an IR-permeable undercoat on the underside of the panel, which is a heat-resistant inorganic enamel paint. In order to provide a heat-resistant cook top, through which the internal parts of the cooking unit cannot be observed, without reducing the strength of the cook top, the inorganic enamel paint includes 70 to 99, preferably 80 to 95, percent by weight of inorganic pigment and from 1 to 30, preferably 5 to 20, percent by weight of glass flux. The glass flux preferably is a borosilicate glass with a thermal expansion coefficient less than or equal to 4*10 −6 K −1 . The coating may be applied by screen printing techniques.

1 . A cook top comprising 
 a transparent, colorless glass ceramic or glass panel providing a cooking surface, said glass ceramic or glass panel being made from pre-stressed special glass; and    an IR-permeable undercoat on an underside of the glass ceramic or glass panel, said IR-permeable undercoating comprising a heat-resistant inorganic enamel paint;    wherein said inorganic enamel paint comprises from 80 to 99 percent by weight of inorganic pigment and from 1 to 20 percent by weight of a lead-free glass flux.    
     
     
         2 . The cook top as defined in  claim 1 , wherein said inorganic enamel paint comprises from 80 to 95 percent by weight of said inorganic pigment and from 5 to 20 percent by weight of said lead-free glass flux.  
     
     
         3 . The cook top as defined in  claim 1 , wherein said lead-free glass flux comprises a lead-free glass with a thermal expansion coefficient less than or equal to 4*10 −6  K −1 .  
     
     
         4 . The cook top as defined in  claim 3 , wherein said lead-free glass flux comprises a lead-free borosilicate glass.  
     
     
         5 . The cook top as defined in  claim 1 , wherein said undercoat is provided on said underside by applying a colored paste to said underside by screen printing and burning in; 
 wherein said colored paste comprises a mixture of paint powder and a screen printing medium.    
     
     
         6 . The cook top as defined in  claim 5 , wherein a ratio of the paint to the screen printing medium amounts to from 0.4 to 2.0.  
     
     
         7 . The cook top as defined in  claim 1 , wherein said undercoat is observation-blocking and stable up to at least 600° C.  
     
     
         8 . The cook top as defined in  claim 1 , wherein said undercoat on said underside is a color-imparting decoration.  
     
     
         9  to  13 . (canceled)  
     
     
         14 . The glass ceramic or glass panel as defined in  claim 1 , having a bending strength of at least 110 Mpa and an impact resistance of greater than 0.5 Nm.  
     
     
         15 . A cook top comprising 
 a transparent, colorless glass ceramic or glass panel providing a cooking surface, said glass ceramic or glass panel being made from pre-stressed glass; and    an IR-permeable opaque observation-blocking undercoat on an underside of the glass ceramic or glass panel, wherein said IR-permeable opaque observation-blocking undercoat consists of a heat-resistant inorganic enamel paint and is stable up to 600° C.; and    wherein said inorganic enamel paint comprises from 80 to 99 percent by weight of an inorganic pigment and from 1 to 20 percent by weight of a lead-free glass flux.    
     
     
         16 . The glass ceramic or glass panel as defined in  claim 15 , wherein said lead-free glass flux comprises a lead-free glass with a thermal expansion coefficient less than or equal to 4*10 −6  K −1 .  
     
     
         17 . The glass ceramic or glass panel as defined in  claim 15 , having a bending strength of at least 110 Mpa and an impact resistance of greater than 0.5 Nm.  
     
     
         18 . The cook top as defined in  claim 15 , wherein said lead-free glass flux is a lead-free borosilicate glass.  
     
     
         19 . The cook top as defined in  claim 15 , wherein said undercoat is applied to said underside by screen printing and burning in.  
     
     
         20 . The cook top as defined in  claim 15 , wherein said undercoat on said underside is a color-imparting decoration.  
     
     
         21 . The cook top as defined in  claim 15 , wherein said lead-free glass flux has a composition, in percent by weight based on oxide content, consisting of:  
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   Al 2 O 3   
                    3-20 
                 
                     
                   BaO 
                   0-4 
                 
                     
                   B 2 O 3   
                   15-27 
                 
                     
                   CaO 
                   0-4 
                 
                     
                   F 
                    0-3, 
                 
                     
                     
                   in exchange for oxygen 
                 
                     
                   K 2 O 
                   <2 
                 
                     
                   Li 2 O 
                   0-6 
                 
                     
                   MgO 
                   0-4 
                 
                     
                   Na 2 O 
                   0-5 
                 
                     
                   SiO 2   
                   43-65 
                 
                     
                   Sb 2 O 3   
                   0-2 
                 
                     
                   SrO 
                   0-4 
                 
                     
                   TiO 2   
                   0-3 
                 
                     
                   ZnO 
                   0-4 
                 
                     
                   ZrO 2   
                   0-4