Pad transfer printing method for making colored contact lenses

A method for producing colored contact lenses, comprising the steps of:

• (1) obtaining a mold which comprises a female mold half having first molding surface and a male mold half having a second molding surface, wherein the male and female mold halves are configured to receive each other such that a lens-forming cavity is formed between the first and second molding surfaces when the mold is closed;
• (2) forming, on the first or second molding surface, a colored transferrable polymeric film, wherein the colored transferrable polymeric film is formed by:
• (a) applying a layer of a first polymerizable composition onto the first or second molding surface, wherein the first polymerizable composition is free of any pigment particle,
• (b) at least partially curing the layer of the first polymerizable composition to form a first polymeric film on the first or second molding surface,
• (c) printing a colored image with at least one ink on the first polymeric film on the first or second molding surface by using a pad printing instrument that comprises a silicone pad, a printing plate having a flat surface with an image pattern engraved thereon, and an ink supply system, wherein the ink supply system comprises (i) an ink cup containing the ink having a first temperature of from about 20° C. to about 30° C., (ii) an ink container containing the ink having a second temperature being at least about 3° C. lower than the first temperature and in flow communication with the ink cup, (iii) a thermostat for maintaining the ink in the ink container at the second temperature, (iv) a first flow conduit, and (v) a second flow conduit, wherein the ink cup comprises a) a cylindrical hollow structure defining an ink reservoir for holding the ink and defining an outer edge, wherein the outer edge having a scraping element thereon for engaging the printing plate, b) an ink cup inlet, c) an ink cup outlet, and d) a stirrer for continuously mixing the ink in the ink cup, wherein the first flow conduit extends between the ink container and the ink cup inlet for providing a flow of the ink having the second temperature from the ink container to the ink cup and for maintaining the temperature of the ink in the ink cup at the first temperature, wherein the second flow conduit extends between the ink container and the ink cup outlet for providing a flow of the ink having the first temperature from the ink cup to the ink container,
• (d) curing the colored images on the first polymeric film on the first or second molding surface, and
• (e) optionally applying a layer of a second polymerizable composition on top of the first polymeric film to completely cover the cured colored image on the first polymeric film, wherein the second polymerizable composition is free of any pigment particle and then is curing at least partially to form the second polymeric film which completely covers the cured colored image;
• (3) dispensing a lens-forming composition into the lens-forming cavity of the mold;
• and
• (4) curing the lens-forming composition within the lens-forming cavity to form the colored contact lens, whereby the colored transferrable polymeric film detaches from the first or second molding surface and becomes integral with the body of the colored contact lens.