Excess polymer ring removal during ophthalmic lens manufacture
The present invention includes molds for forming ophtalmic lenses, such as contact lens. In particular, the present invention relates to apparatus, molds and methods for fashioning an ophthalmic lens with a mold assembly that includes two or more mold parts with at least one of the mold parts including a flange surface and a static charge differential between each mold part, including the flange surface.
1. A method of molding an ophthalmic lens, the method comprising the steps of:
forming multiple mold assemblies, each mold assembly comprising a first mold part and a second mold part and each mold part comprising an optical surface portion;
imparting a static charge differential between multiple sets of first mold parts and second mold parts, wherein at least the second mold part comprises a flange and the static charge differential comprises a negative charge imparted to the respective second mold parts across a lens forming surface, relative to the first mold part and the static charge is imparted via a static bar;
dosing a reaction mixture into the first mold parts;
coupling respective second mold parts to the first mold parts thereby forming a cavity therebetween, with the reaction mixture formed to a shape of the cavity and the reaction mixture also formed into a ring in contact with the flange surface of the second mold parts;
exposing the reaction mixture to actinic radiation thereby forming an ophthalmic lens in the respective multiple mold assemblies and also forming an excess polymer ring in at least some of the multiple mold assemblies;
decoupling the second mold part from the first mold part;
automatically inspecting the multiple ophthalmic lenses formed and corresponding first mold parts for excess polymer ring defects;
designating an incidence of polymeric ring attachment to one or both of: formed ophthalmic lenses and respective first mold parts containing the formed ophthalmic lens with no static charge applied; and
determining a decreased incidence of excess polymer rings attached to one or both of: the multiple ophthalmic lenses formed and the corresponding first mold parts with the imparting a static charge differential between each set of first mold parts and second mold parts, as compared to similar mold parts without a static charge differential.
2. The method of claim 1 wherein the static charge differential imparted between the first mold part and the second mold part is of about 30 kV.
3. The method of claim 1 wherein the static charge differential imparted between the first mold part and the second mold part is within a range of about 0.5 kV and 5.0 kV.
4. The method of claim 1 wherein the static charge differential imparted between the first mold part and the second mold part is within a range of about 0.5 kV and 0.05 kV.
5. The method of claim 1 additionally comprising the steps of:
discharging static charge from at least one of the first mold part and the second mold part; and
transporting the least one of the first mold and the second mold part from which static has been discharged on a transport apparatus.
6. The method of claim 1 wherein at least one of the first mold part and the second mold part comprises polyvinyl alcohol.
7. The method of claim 1 wherein at least one of the first mold part and the second mold part comprises polypropylene.
8. The method of claim 2 wherein the automatic lens inspection for delamination indicates a less than 1% incidence of ophthalmic excess polymer ring defect.
9. The method of claim 2 wherein the automatic lens inspection for delamination indicates a less than 20% incidence of ophthalmic excess polymer ring defect.