Lithium disilicate glass-ceramic, method for production thereof and use thereof

Abstract

The invention relates to glass-ceramics based on the lithium silicate system which can be mechanically machined easily in an intermediate step of crystallisation and, after complete crystallisation, represent a very strong, highly-translucent and chemically-stable glass-ceramic. Likewise, the invention relates to a method for the production of these glass-ceramics. The glass-ceramics according to the invention are used as dental material.

1 . A lithium disilicate glass-ceramic comprising at least 10% by weight of a stabiliser in order to increase the chemical and mechanical stability, the stabiliser being present essentially in the amorphous phase. 
     
     
         2 . The lithium disilicate glass-ceramic according to  claim 1 , wherein the stabiliser is selected from the group consisting of zirconium oxide, hafnium oxide and mixtures hereof. 
     
     
         3 . The lithium disilicate glass-ceramic according to  claim 2  having the following composition:
 55 to 70% by weight of SiO 2 , 
 10 to 15% by weight of LiO 2 , 
 10 to 20% by weight of the stabiliser selected from the group consisting of ZrO 2 , HfO 2  or mixtures hereof, 
 0.1 to 5% by weight of K 2 O, 
 0.1 to 5% by weight of Al 2 O 3 , 
 0 to 10% by weight of additives and also 
 0 to 10% by weight of colourants. 
 
     
     
         4 . The lithium disilicate glass-ceramic according to  claim 3 , wherein the colourants are glass-colouring oxides and/or pigments. 
     
     
         5 . The lithium disilicate glass-ceramic according to  claim 4 , wherein the glass-colouring oxides are selected from the group of the oxides of iron, titanium, cerium, copper, chromium, cobalt, nickel, manganese, selenium, silver, indium, gold, rare earth metals, in particular neodymium, praseodymium, samarium and europium. 
     
     
         6 . The lithium disilicate glass-ceramic according to  claim 4 , wherein the pigments are doped spinels. 
     
     
         7 . The lithium disilicate glass-ceramic according to  claim 3 , wherein the additives are selected from the group consisting of boron oxide, phosphorus oxide, fluorine, sodium oxide, barium oxide, strontium oxide, magnesium oxide, zinc oxide, calcium oxide, yttrium oxide, titanium oxide, niobium oxide, tantalum oxide, lanthanum oxide and mixtures hereof. 
     
     
         8 . The lithium disilicate glass-ceramic according to  claim 3  having the following composition:
 58 to 64% by weight of SiO 2 , 
 11 to 13% by weight of LiO 2 , 
 10 to 15% by weight of the stabiliser selected from the group consisting of ZrO 2 , HfO 2  or mixtures hereof, 
 2 to 5% by weight of K 2 O, 
 2 to 5% of Al 2 O 3 , 
 2 to 5% of P 2 O 5  and also 
 0 to 5% by weight of additives and also 
 0 to 10% by weight of colourants. 
 
     
     
         9 . A method for the production of a lithium disilicate glass-ceramic according to  claim 3 , wherein
 a) an initial glass is produced which comprises the components of the glass-ceramic,   b) the initial glass is subjected to a first heat treatment in order to produce a glass-ceramic which has lithium metasilicate as main crystal phase,   c) the glass-ceramic of b) is subjected to a second heat treatment in which the lithium metasilicate is converted with SiO 2  from the glass phase into lithium disilicate and subsequently lithium disilicate is present as main crystal phase.   
     
     
         10 . The method according to  claim 9 , wherein the first heat treatment is effected at a temperature of 620° C. to 800° C. over a period of time of 1 to 200 min, in particular of 650° C. to 750° C. over a period of time of 10 to 60 min. 
     
     
         11 . The method according to  claim 9 , wherein the second heat treatment is effected at a temperature of 800° C. to 1,040° C. over a period of time of 5 to 200 min, in particular of 650° C. to 750° C. over a period of time of 5 to 30 min. 
     
     
         12 . The lithium disilicate glass-ceramic of  claim 3 , wherein the glass-ceramic is a dental material or component of a dental material. 
     
     
         13 . The lithium disilicate glass-ceramic of  claim 12  in the form of an inlay, an onlay, a bridge, a pin construction, a veneer, a (partial) crown.