| 摘要 |
An article having a lithia-alumina-magnesia-silica glass base has a film of a crystal nucleating material applied to the surface thereof, the coated glass then being heat-treated to develop crystals in the glass surface. The nucleating agent is preferably titanium dioxide but may be silver. In the case of titanium a titanium containing material, capable of forming titanium dioxide on heating, is dissolved in a solvent and coated on to the glass surface. The titanium is preferably present in an amount of from 0.01 to 5% by weight and may contain 0.01 to 2% by wt. of a soluble iron salt. The coating is carried out at a temperature of from 65 DEG to 75 DEG F. and the subsequent heat treatment at from 100 DEG to 200 DEG F. below the softening point of the glass, e.g. at 1300 DEG to 1575 DEG F. for from 5 to 30 minutes. The film of nucleating agent should have a thickness of from 0.001 to 0.05 microns. The final article should be transparent and if in sheet form have a surface compressive stress in the crystallized zone of at least 50,000 p.s.i. A suitable glass composition is such as disclosed in Specification 1,089,912.ALSO:An article having a lithia-alumina-magnesia-silica glass base has a film of a crystal nucleating material applied to the surface thereof the coated glass then being heat treated to develop crystals in the glass surface. The nucleating agent is preferably titanium but may be silver. The base glass article is coated by either being dipped in, or having sprayed thereon, a solution or dispersion of a titanium compound or composition. The film may be either a titanium compound or a titanium containing composition but must be capable of yielding a clear film of titanium dioxide at temperatures in the range 1250 DEG to 1450 DEG F, the film having a thickness of from 0.001 to 0.05 microns. The coating is carried out at temperatures in the range 65 DEG to 75 DEG F and a relative humidity of less than 40% and preferably below 25%. A list is given of suitable titanium containing materials, particularly organic titanium containing materials. The titanium is preferably present in the coating solution or dispersion in an amount of from 0.01 to 5% by wt. and there may be present from 0.01 to 2% of a soluble iron salt. |
