| 摘要 |
<p>This invention is directed to the preparation of glass articles exhibiting a relatively broad band of high contrast polarizing properties in the infrared region of the radiation spectrum from glasses containing silver halide particles selected from the group consisting of AgCl, AgBr, and AgI. The inventive method comprises the following five general steps: (a) melting a batch for a glass containing silver and at least one halide selected from the group consisting of chloride, bromide, and iodide; (b) cooling and shaping said melt into a glass article of a desired configuration; (c) subjecting said glass article to a temperature at least above the strain point, but not in excess of 75 DEG C above the softening point of the glass, for a sufficient length of time to cause the generation of silver halide particles therein selected from the group consisting of AgCl, AgBr, and AgI, said particles ranging in size between about 200-5000 ANGSTROM ; (d) elongating said glass article under stress at a temperature above the annealing point, but below that where said glass exhibits a viscosity of about 10<8> poises, such that said silver halide particles are elongated to an aspect ratio of at least 5:1 and aligned in the direction of the stress; and, thereafter, (e) exposing said elongated glass article to a reducing environment at a pressure greater than atmospheric pressure and at a temperature above about 250 DEG C, but no higher than about 25 DEG C above the annealing point of the glass, for a period of time sufficient to develop a reducing surface layer on said glass article having a thickness of at least 10 microns wherein at least a portion of said elongated silver halide particles are reduced to elemental silver particles having aspect ratios greater than 2:1 which are deposited in and/or upon said elongated particles. The single figure illustrates the improved contrast and bandwidth achieved by the process (curves B, C and D).</p> |
