Injection mold design, method for in-mold coating of lenses, and coated lenses
View Patent ↗A method and apparatus for coating lenses within an injection molding machine having a concave optical insert with a perimeter edge that meets the receiver ring in an annular contact region. A channel is formed throughout the annular contact region. When molding a lens with the apparatus, and according to the method, a closed-loop coating containment lip is formed by the channel. After the lens has solidified and the mold is opened, a predetermined volume of coating solution is applied and the mold is re-clamped. A uniformly thin layer of coating is cured on to the convex lens surface by avoiding coating run off and preventing mold contamination.
1. A method of coating lenses in an injection molding machine having a concave optical insert with a perimeter edge that meets two receiver rings in an annular contact region, comprising the steps of:
providing a molding cavity with a channel formed throughout the annular contact region, wherein the channel is formed within the two receiver rings and spans the parting line;
injection molding a lens within the cavity whereby a coating containment lip is formed by the channel at the lens periphery; and
dispensing a coating solution on to the lens so that the lip contains the coating during coating application spread.
2. The method of claim 1 , wherein said dispensing step comprises: dispensing a predetermined volume of coating solution to insure lip containment so that a uniformly thin coating layer is provided across the entire lens surface.
3. The method of claim 1 , wherein said dispensing step comprises: dispensing a predetermined volume of coating solution to insure lip containment so that coating run off is avoided to prevent contamination of the mold.
4. The method of claim 1 , wherein the channel is formed with an open cross-sectional geometry to allow the injection molding machine to open, with the insert and receiver cleanly pulling away from the lens and the lip.
5. The method of claim 4 , wherein the channel forms an interior wall of the lip at an angle from greater than 0 degrees to 90 degrees.
6. The method of claim 4 , wherein the lip has a height in the range of 0.25 mm to 10 mm.
7. The method of claim 4 , wherein following said injection molding step, the molding machine opens and the coating solution is dispensed; and wherein coating application spread is achieved by closing the molding machine.
8. The method of claim 1 , wherein the concave optical insert is removable.
9. The method of claim 8 , wherein the concave optical insert has a bifocal part-forming surface.
10. The method of claim 1 , wherein the concave optical insert has a bifocal part-forming surface.
11. The method of claim 1 , wherein the injection molding step comprises delivering molten thermoplastic material through an edge gate formed in one of the receiver rings.
12. The method of claim 1 , wherein the channel is formed by grooving at least one of the receiver rings.
13. The method of claim 1 , wherein the channel is formed by chamfering at least one of the receiver rings.