Method and device for producing thin glass panes

Abstract

The invention relates to a method for producing thin glass panes, especially glass panes with a thickness of below 1 mm, by drawing a thin glass strand vertically downwards. According to the inventive method, a glass melt is fed from a melting bath via a feed to the glass drawing tank that comprises a nozzle system with at least one slotted nozzle. The length and the diameter of the feed as well as the viscosity of the glass melt present in the feed determine the overall throughput. The throughput per length unit in the transverse direction to the glass strand (so-called line throughput) is adjusted via the geometry of the nozzle system and via the viscosity of the glass melt present in the nozzle system. These parameters are adjusted in such a manner that the glass, when leaving the nozzle system, does not wet the bottom of the slotted nozzle in the range of the tearoff edge. The invention further relates to a device for producing thin glass panes which is characterized in that the feed ( 1 ), the glass drawing tank ( 6 ) and the nozzle system form a closed system. The feed ( 1 ) is provided with a tube ( 2 ) with segmented tube sections ( 2 a, b, c ) that has a length of from 2 m to 5 m and a diameter of from 50 mm to 80 mm, the tube cross-section being circular. The glass drawing tank is provided with a heating system ( 9 ) that is vertically and transversely segmented.

1 . A method for producing thin glass panes, in particular glass panes with a thickness of less than 1 mm, by drawing a thin glass ribbon vertically downward, in which a glass melt is conveyed from a tank furnace, through an inlet, and to a drawing tank with a nozzle system that has at least one slit nozzle, characterized in that 
 on the one hand, the total throughput is set by means of the length and cross section of the inlet and by means of the viscosity of the glass melt disposed in the inlet and    on the other hand, the throughput per unit of length in the lateral direction of the glass ribbon (so-called linear throughput) is set by means of the geometry of the nozzle system and by means of the viscosity of the glass melt disposed in the nozzle system,    and in that upon emerging from the nozzle system, the glass does not wet the underside of the slit nozzle in the vicinity of the breaking edge.    
     
     
         2 . The method according to  claim 1 , characterized in that the temperature of the glass melt in the inlet channel is set to T ZR1 =Tg+670 K to T ZR2 =Tg+590 K.  
     
     
         3 . The method according to  claim 1  or  2 , characterized in that the temperature of the glass melt in the drawing tank is set to T ZT1 =Tg+590 K to T ZT2 =Tg+570 K.  
     
     
         4 . The method according to one of  claims 1  to  3 , characterized in that the temperature TSD of the glass melt in the vicinity of the slit nozzle is set to T SD1 =Tg+570 K to =Tg+550 K.  
     
     
         5 . The method according to one of  claims 1  to  4 , characterized in that the temperature deviation ΔT SD  of the glass melt along the slit nozzle is set to ΔT SD </=20 K.  
     
     
         6 . The method according to one of  claims 1  to  5 , characterized in that the glass melt flow, upon passing through the slit nozzle, is split by at least one draw bar, wherein the glass melt travels downward in the form of a glass film on both sides of the draw bar and comes together to form one glass ribbon at the bottom end of the draw bar.  
     
     
         7 . The method according to  claim 6 , characterized in that the dwell time and the viscosity of the glass films on the draw bar are adjusted in such a way that deviations from the ideal surface contour heal almost completely.  
     
     
         8 . The method according to one of claims  6  or  7 , characterized in that the glass films are selectively heated and/or cooled on the draw bar.  
     
     
         9 . The method according to one of  claims 6  to  8 , characterized in that the glass films are laterally guided along their side edges.  
     
     
         10 . The method according to one of  claims 6  to  9 , characterized in that the glass ribbon is selectively cooled in the vicinity of its onion.  
     
     
         11 . The method according to one of  claims 1  to  10 , characterized in that at least a part of the weight of the glass ribbon is compensated for during drawing.  
     
     
         12 . The method according to one of  claims 1  to  11 , characterized in that the thickness of the glass ribbon is continuously measured and that the drawing speed is controlled by means of the measured thickness values.  
     
     
         13 . The method according to one of  claims 1  to  12 , characterized in that the glass ribbon is stretched lateral to the ribbon direction in the viscoelastic region.  
     
     
         14 . The method according to one of  claims 1  to  13 , characterized in that the glass ribbon is selectively heated and/or cooled both in the ribbon direction and lateral to the ribbon direction, in the rolling furnace and/or in the drawing shaft.  
     
     
         15 . A device for producing thin glass panes, in particular glass panes with a thickness of less than 1 mm, with a tank furnace, a homogenization system, an inlet, and a drawing tank, wherein the drawing tank has a nozzle system with at least one slit nozzle, characterized in that 
 the inlet ( 1 ), the drawing tank ( 6 ), and the nozzle system constitute a closed system,    in that the inlet ( 1 ) has a tube ( 2 ) with segmented tube sections ( 2   a, b, c ), wherein the tube ( 2 ) has a length of 2 to 5 m and a cross section of 50 mm to 80 mm, wherein the tube cross section is circular, and    in that the drawing tank ( 6 ) has a heating system ( 9 ) that is segmented in the vertical and lateral direction.    
     
     
         16 . The device according to  claim 15 , characterized in that the tube ( 2 ) is situated vertically.  
     
     
         17 . The device according to one of claims  15  or  16 , characterized in that the inlet ( 1 ) has a segmented heating and cooling unit ( 3 ,  4 ).  
     
     
         18 . The device according to one of  claims 15  to  17 , characterized in that the slit nozzle ( 11 ) has a heating unit ( 15 ).  
     
     
         19 . The device according to one of  claims 15  to  18 , characterized in that the slit nozzle ( 11 ) contains at least one vertically situated draw bar ( 16 ).  
     
     
         20 . The device according to one of  claims 15  to  19 , characterized in that the draw bar ( 16 ) is a plate made of a platinum alloy that tapers down to a point at the bottom.  
     
     
         21 . The device according to one of  claims 15  to  20 , characterized in that the draw bar ( 16 ) protrudes upward beyond the slit nozzle ( 11 ).  
     
     
         22 . The device according to one of  claims 15  to  21 , characterized in that the draw bar ( 16 ) has side limiters ( 17 ).  
     
     
         23 . The device according to one of  claims 15  to  22 , characterized in that the draw bar ( 16 ) can be adjusted in the X-, Y-, and Z-direction.  
     
     
         24 . The device according to one of  claims 15  to  23 , characterized in that the draw bar ( 16 ) can be stretched in the X-direction through exertion of a tensile force.  
     
     
         25 . The device according to one of  claims 15  to  24 , characterized in that the draw bar ( 16 ) has a heating unit and/or a cooling unit.  
     
     
         26 . The device according to one of  claims 15  to  25 , characterized in that the slit nozzle ( 11 ) is adjoined on the underside by a nozzle furnace ( 18 ) with a segmented heating and cooling device ( 20 ,  23 ,  24 ).  
     
     
         27 . The device according to  claim 26 , characterized in that the nozzle furnace ( 18 ) has radiation plates ( 19 ) on the surfaces opposite the draw bar ( 16 ).  
     
     
         28 . The device according to one of claims  26  or  27 , characterized in that the nozzle furnace ( 18 ) has at least one movable dividing wall ( 22 ) underneath the radiation plates ( 19 ).  
     
     
         29 . The device according to one of  claims 26  to  28 , characterized in that the nozzle furnace ( 18 ) has means that allow it to be opened lateral to the ribbon direction.  
     
     
         30 . The device according to one of  claims 26  to  29 , characterized in that the nozzle furnace ( 18 ) is adjoined from underneath by a rolling furnace ( 25 ) with a rolling shaft ( 26 ), which has a heating and cooling unit ( 27 ,  28 ) that is segmented in the X- and Y-directions.  
     
     
         31 . The device according to  claim 29 , characterized in that the rolling shaft ( 41 ) contains at least one warp roller pair ( 29 ) and/or drawing roller pair ( 30 ).  
     
     
         32 . The device according to one of  claims 29  to  31 , characterized in that the rolling furnace ( 25 ) has means that allow it to be opened lateral to the ribbon direction.  
     
     
         33 . The device according to one of  claims 15  to  32 , characterized in that the drawing speed of the drawing rollers ( 30 ) can be regulated as a function of the on-line total thickness of the glass ribbon.  
     
     
         34 . The device according to one of  claims 15  to  33 , characterized in that the drawing shaft can be telescoped out and in, downward or to the side.  
     
     
         35 . The use of the glass panes produced with the method according to one of  claims 1  to  15  as substrate glass in electronic devices or as substrate glass for mass storage devices of computers.