Patent ID: 7811485

Claim:
A method for making at least one optical plate, comprising: heating a first transparent matrix resin to a melted state; heating a second transparent matrix resin mixed with diffusion particles to a melted state; heating a third transparent matrix resin to a melted state; injecting the melted first transparent matrix resin into a first molding chamber of a multi-shot injection mold to form a first transparent layer of the at least one optical plate, the multi-shot injection mold including a first mold and at least one second mold, the first mold defining at least one molding cavity receiving the at least one second mold, the first mold including a plurality of first spherical depressions formed at an inmost end of the at least one molding cavity, the second mold including a plurality of second spherical depressions formed at the molding surface, a portion of the at least one molding cavity and the at least one second mold cooperatively forming the first molding chamber; moving the at least one second mold a distance away from the inmost end of the at least one molding cavity of the first mold; injecting the melted second transparent matrix resin mixed with diffusion particles into a second molding chamber of the multi-shot injection mold to form a light diffusion layer of the at least one optical plate on the first transparent layer, a portion of the at least one molding cavity, the first transparent layer, and the at least one second mold cooperatively forming the second molding chamber; moving the at least one second mold a further distance away from the inmost end of the at least one molding cavity of the first mold; injecting the melted third transparent matrix resin into a third molding chamber of the multi-shot injection mold to form a second transparent layer of the at least one optical plate on the light diffusion layer, a portion of the at least one molding cavity, the first transparent layer, the light diffusion layer, and the at least one second mold cooperatively forming the third molding chamber; taking the combined first transparent layer, light diffusion layer and second transparent layer out of the at least one molding cavity of the first mold, wherein a thickness of each of the first transparent layer, the light diffusion layer, and the second transparent layer is greater than or equal to 0.35 millimeters.