Cone glass for a display tube, method of preparing the cone glass and products obtained therefrom

Abstract

The invention relates to a method of preparing a cone glass for a display tube. The cone glass according to the invention is obtained by mixing a first portion of glass fragments having a known composition with a second portion of vitrifying materials, wherein the first portion contains glass fragments of cone glass and screen glass of a display tube, and wherein the composition of the second portion is chosen to be such that at least one of the physical properties of X-ray absorption, electrical resistance, thermal coefficient of expansion and viscosity is in a desired range.

1 . A cone glass for a display tube, which cone glass contains the following components: 
 1.7-2.3% by weight of Al 2 O 3 ,    6.0-6.5% by weight of Na 2 O    7.3-7.8% by weight of K 2 O,    2.0-2.6% by weight of MgO,    2.9-3.7% by weight of CaO,    0.2-2.2% by weight of SrO,    0.2-2.6% by weight of BaO,    20.5-23% by weight of PbO,    0.1-0.3% by weight of Sb 2 O 3 ,    0.1-0.6% by weight of ZrO 2 ,    up to 0.3% by weight of impurities    rest, i.e. 48-59% by weight of SiO 2 .    
     
     
         2 . A cone glass as claimed in  claim 1 , characterized in that the composition of the components in the cone glass is chosen to be such that the X-ray absorption is minimally 64.8 cm −1 .  
     
     
         3 . A cone glass as claimed in  claim 1 , characterized in that the thermal coefficient of expansion of the cone glass is between 9.8*10 −6 K −1  and 10.0*10 −6 K −1 .  
     
     
         4 . A cone glass as claimed in  claim 1 , characterized in that the logarithm of the electrical resistance of the glass, measured at a temperature of 250° C., is minimally 9.6 Ωcm.  
     
     
         5 . A cone glass as claimed in  claim 1 , characterized in that the cone glass has a viscosity of 10 4  Pa·s at a temperature between 955° C. and 965° C.  
     
     
         6 . A cone for a display tube obtained from cone glass as claimed in any one of the preceding claims  1 ,  2 ,  3 ,  4  or  5 .  
     
     
         7 . A method of preparing cone glass for a display tube by mixing a first portion of glass fragments having a known composition with a second portion of vitrifying materials, in which a quantity of one or more X-ray-absorbing oxides in the second portion is chosen to be such that the cone glass has an X-ray absorption of minimally 64.8 cm −1 .  
     
     
         8 . A method as claimed in  claim 7 , wherein the quantities of Al 2 O 3 , Na 2 O, K 2 O, MgO and CaO in the second portion are chosen to be such that the logarithm of the electrical resistance of the cone glass, measured at a temperature of 250° C., is minimally 9.6 Ωcm.  
     
     
         9 . A method as claimed in  claim 7 , wherein the quantities of Al 2 O 3 , Na 2 O, K 2 O, MgO and CaO in the second portion are chosen to be such that the thermal coefficient of expansion of the cone glass is between 9.8*10 −6  K −1  and 10.0*10 −6  K −1 .  
     
     
         10 . A method as claimed in  claim 7 , wherein the quantities of Al 2 O 3 , Na 2 O, K 2 O, MgO and CaO in the second portion are chosen to be such that the cone glass has a viscosity of 10 4  Pa·s at a temperature between 955° C. and 965° C.  
     
     
         11 . A method of preparing cone glass for a display tube by mixing a first portion of glass fragments having a known composition with a second portion of vitrifying materials, in which the first portion comprises fragments of cone glass and screen glass of a display tube and in which the composition of the second portion is chosen to be such that at least one of the physical properties of X-ray absorption, electrical resistance, thermal coefficient of expansion and viscosity is in a desired range.