Method for tinting hydrophilic plastic articles

Abstract

Tinted hydrophilic plastic articles, such as soft contact lenses, are prepared by carrying out the tinting operation while the hydrophilic material is still in its non-hydrated state. Tinting at this point avoids the need for use of swelling agents and also permits integration of the tinting procedure into an overall automated manufacturing operation. A preferred embodiment of the invention is an integrated process for producing a tinted soft contact lens comprising the steps of providing a casting mold having an arbor formed as a cup shaped container, filling said container with a monomeric lens forming liquid, polymerizing said liquid to produce a lens blank having one optical surface formed by the bottom of said cup shaped container, generating (e.g., machining) a second optical surface on said blank while said casting mold is mounted on a precision mandrel, tinting said resulting lens by impregnating the pores of said blank with a dispersion of a solubilized vat dye precursor and subsequently precipitatintg an insoluble vat dye within said pores, the blank being rinsed both before and after precipitation of said vat dye while still mounted in said casting mold, drying said blank to return it to a substantially xerogel state, edging and further processing said blank to convert it into a tinted hydrated soft contact lens, and subsequently hydrating said lens. While the foregoing is the preferred embodiment, the method may be utilized at the xerogel stage in all other presently known methods of forming lenses, e.g., lathing, cast molding and spin casting.