Ink formulations and uses thereof

An ink comprising:

• a solvent;
• a colorant;
• and a binder polymer, wherein the colorant comprises pigments, wherein the binder polymer is a polymer which comprises multiple olefinically unsaturated groups and is capable of being crosslinked under free radical polymerization conditions in the absence of a crosslinker to form inter- and intra crosslinkages so that a macromolecular matrix is formed to bind and/or trap pigments onto a soft contact lens and to ensure no visible and microscopic (˜10×) observation of colorant bleeding, smearing, or delamination in a color image printed on the contact lens with said ink, wherein each intra-crosslinkage is an intramolecular covalent bond formed between a pair of olefinically unsaturated groups which belong to the same binder polymer molecule, wherein the inter-crosslinkage is an intermolecular covalent bond formed between a pair of olefinically unsaturated groups each belonging to one of two binder polymer molecules, wherein the ink is characterized by having a surface tension of from about 20 mN/m to about 60 mN/m, a viscosity of less than 50 centipoise, and good adhesion to a soft contact lens and by being stable for at least about 4 hours, wherein a color image printed on the soft contact lens with said ink passes a sterilization surviving test, and wherein the binder polymer is a cellulosic resin, polyester, polyurethane, polyurea, or polyamides, wherein the amount of the solvent is from about 60% to 99% by weight, wherein the amount of the binder polymer is from about 1% to about 30% by weight, and wherein the amount of the colorant is from about 0 to about 15% by weight.