Deposition of silver layer on nonconducting substrate

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with a preferred aspect of the invention, a process for depositing a uniform thin layer of silver onto the surface of an electrically non-conducting substrate comprises the steps of cleaning the surface in an aqueous cleaning solution; activating the surface in an aqueous activating solution containing at least about 0.
001 grams per liter of a salt containing stannous tin ions; depositing silver onto the surface from a deposition solution having a pH of not less than about 8, and containing silver nitrate, a reduction agent selected from the group consisting of formaldehyde, hydrazine sulfate, hydrazine hydroxide, and hypophosphoric acid, in a concentration sufficient to reduce the silver salt to form metallic silver at the surface of the substrate, and a deposition control agent selected from the group consisting of invertose, succinate acid, sodium citrate, sodium acetate, sodium hydroxide, potassium hydroxide, and ammonia in a concentration sufficient to prevent the silver in the solution from precipitating from the solution, and to permit it to deposit upon the surface of the substrate, the step of depositing being accomplished in darkness; and stabilizing the deposited silver by contacting the surface upon which colloidal silver has deposited for at least about 5 seconds with a stabilizing solution of at least about 0.
001 grams per liter of a salt of a metal selected from a member of the platinum group and gold dissolved in dilute nitric acid, the resulting solution having a pH value of from about 3.
0 to about 4.
8.
The present invention is operable in depositing a colloidal metallic silver layer upon the surfaces of many different nonconducting substrate materials.
The substrate may itself be a flexible film, or may be a rigid solid.
Such materials include, by way of example and not limitation, latex, polystyrene, polyester, polyvinylchloride, polyurethane, ABS polymers, ceramics such as aluminum oxide, glass, polyamide, polyimide, polycarbonate, and synthetic rubber