Method for injection molding plus power lens elements

A method for injection molding of a plus power lens element, comprising:

• injecting a melt of thermoplastic material comprising at least one UV absorber at a temperature higher than a glass transition temperature (Tg) of said thermoplastic material in an initial molding cavity delimited by two facing mold inserts;
• during said injecting, moving said two facing mold inserts toward one another to define a final molding cavity whose volume is less than that of said initial molding cavity;
• and
• after cooling and opening of the molding cavity, recovering said plus power lens element,
• wherein one of said two facing mold inserts comprises a flat surface facing said initial molding cavity, thereby to form a flat surface on one side of said plus power lens element,
• wherein the other of said two facing mold inserts comprises a concave surface facing the initial molding cavity, thereby to form a convex surface on an opposite side of the plus power lens element,
• wherein an edge distance between said two facing mold inserts when delimiting said initial molding cavity is not more than 2.5 times an edge thickness of the plus power lens element,
• wherein said moving of the two facing mold inserts toward one another is effected at a speed of greater than 100 mm/s, and
• wherein said injecting is performed at a speed of greater than about 50 mm/s.