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Abstract

An improved method and apparatus for high-pressure injection or compression molding of optical thermoplastic parts such as lenses or optical disks, wherein the optical surfaces of a molded part are formed by intimate contact with suitably contoured or profiled and lapped surfaces of one or more optical mold insert elements. The optical surface of such mold element is of a different composition metallurgically than is the bulk composition of the rest of the mold element, thus allowing for optimum selection for materials-of-construction parameters (such as heat transfer, load-bearing quality, and ease of fabrication) in the bulk properties of the substrate metal, without necessarily trading off against optimum optical surface characteristics (such as imperviousness to chemical oxidation or attack, resistance to scratching and abrasion, ease of generating optical surface therein). Thus, a one-piece construction (not mechanically joined from separate elements) of a seamless nature, generally consists of at least one layer of relatively thick electroplating (nickel or chromium) onto a beryllium-copper alloy substrate of certain specified mechanical and thermal characteristics. Heat transfer is further improved by means of machined flow channels provided for circulating liquid coolants. A most preferred mold element construction consists of, first, a machined beryllium-copper substrate onto which a thick watts nickel plating was deposited, followed by abrasive lapping to create the specified surface contour to a high level of microstructure perfection and smoothness, onto which a final thin hardcasting of either vacuum-deposited TiN or flash plate of chromium is deposited.

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First Claim