| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive lens which improves the durability of a metal die for molding and has optical characteristics equal with conventional one by applying roundness to the cross-sectional form of respective parts of the lens. SOLUTION: The form of a lens 40 has the form of prism, spherical surface or non-spherical surface and roundness 41 at the valley part of the lens is preferably settled within the range of radius from 2 to 3μm m but is not especially limited. As the material of the lens 40, there is transparent optical resin such as polystyrene resin, polyolefin resin, acrylic resin, polycarbonate resin or vinyl chloride resin, for example. Besides, an ultraviolet or electron beam curing resin can be used as well. Concerning a metal die 50 to be molded, it is preferable that copper plating is performed to an iron core, a metal die having a prescribed shape is prepared by performing cutting work to this plating layer with a diamond bite and the metal die performing nickel plating through electrolytic or nonelectrolytic nickel plating to a metal die molding surface is to be used.
|
