Method for marking a water-absorptive contact lens: dyeing dry lens with a mark using reduced vat dye and then making the dye insoluble

摘要

A method for tinting a water-absorptive contact lens to have a mark tinted thereon, which comprises superimposing on a water-absorptive contact lens in the dry state a screen provided with a tinting pattern corresponding to the mark to be tinted on the contact lens, applying to the contact lens through the tinting pattern of the screen a dye solution containing a vat dye and an alkaline reducing agent, followed by insolubilizing the vat dye.