Corning Glass Works

Leon M Sanford

Paul A Tick

Che-Kuang Wu

Roger F Bartholomew

William L Haynes

Glass compositions in the tin-phosphorus-oxyfluoride composition system exhibiting very low glass transition temperatures and capable of being modified by the addition of selected constituents to exhibit excellent stability in a humid environment, are described.

Tin-phosphorus oxyfluoride glasses

The instant invention is concerned with the production of glasses which are capable of being molded or otherwise shaped under pressure at temperatures not exceeding about 450.degree. C. Such glasses consist essentially, in mole percent as analyzed on the oxide basis, of at least 20% but less than 50% P.sub.2 O.sub.5, 15-45% R.sub.2 O, wherein R.sub.2 O consists of 0-45% Li.sub.2 O, 0-20% Na.sub.2 O, and 0-10% K.sub.2 O, and 0-20% RO, wherein RO consists of 0-10% MgO, 0-15% CaO, 0-20% SrO, and 0-20% BaO, with about 0.3-3% by weight F as analyzed in the final glass. Useful additions to the base compositions include PbO, La.sub.2 O.sub.3, ZnO, and B.sub.2 O.sub.3.

Moldable glasses

The present invention is concerned with the production of sodium and/or potassium hydrosilicate glass bodies. The basis of the invention resides in the hydration of anhydrous sodium and/or potassium silicate glass bodies in aqueous alcohol solutions to impart enhanced mechanical strength and thermoplastic properties thereto. The hydrating process, which permits close control to be maintained over the water content absorbed in the glass, can be carried out in liquid solutions of water and relatively short chain, i.e. up to about five carbon atoms, aliphatic alcohols or in gaseous atmospheres of such solutions. An ion exchange reaction of Li.sup.+ ions or protons with Na.sup.+ and/or K.sup.+ ions can be promoted at temperatures above the transformation range of the hydrated glass, and an exchange of K.sup.+ ions for Na.sup.+ and/or Li.sup.+ ions at temperatures below the transformation range. The invention also contemplates treating sodium and/or potassium hydrosilicate glass bodies, produced through the previous hydration of sodium and/or potassium silicate glass bodies, in a gaseous or liquid alcohol or water-alcohol mixture to impart increased strength and impact resistance thereto and alter the absorbed water content therein. The aforementioned ion exchange reactions are also applicable here.

Hydration of silicate glasses in alcohol-water solutions

An optical glass article having a desired surface figure and demonstrating maximum theoretical light transmission can be prepared by forming a base anhydrous glass of defined compositional ranges, hydrating the glass, partially dehydrating the glass at a temperature above the softening point and, using an inert gas, at a pressure above the vapor pressure of water contained therein, and then molding a preformed blank of the glass against a die having a desired optical quality surface figure, the molding being under conditions sufficient to transfer the surface figure of the die to the glass. The base glass comprises, in mole percent, about 70 to 82% SiO.sub.2, 10 to 17% Na.sub.2 O and/or K.sub.2 O, and 5 to 15% of an oxide or oxides selected from ZnO and PbO. The water content of the partially dehydrated glass ranges from about 3 to 8 wt. percent and the molded glass has a substantially uniform refractive index throughout its bulk. Homogeneous distribution of the water throughout the glass bulk appears to be assured by limiting the total water content to a range at which the diffusion coefficient of the water species (H.sub.2 O, H.sup.+, and OH.sup.-) exhibits the greatest dependence on the total water concentration (i.e. the range at which the coefficient is a quasi-step function).

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Corning, NY, United States of America

Leon M Sanford