B - Operations – Transporting – 29 – D
Patent
B - Operations, Transporting
29
D
B29D 11/02 (2006.01) A61F 2/16 (2006.01) B29C 59/02 (2006.01)
Patent
CA 2058409
A method for manufacturing an intraocular lens from a cell cast sheet of high molecular weight polymethylmethracrylate (PMMA). A lens blank 30 having a lens generation area 31 with a surface contoured to correspond to the desired contour of the finished lens 10 is machined from the sheet of PMMA to a predetermined precompensated size larger than desired to accommodate normalizing shrinkage. The lens blank 30 is normalized by heating the blank in a vacuum oven. The vacuum is released from the oven by introducing dry nitrogen. A stamping die 54 is provided. An optical embossing surface 56 of the stamping die is contoured as a physical negative of the lens generation area 31 and bears a physical negative of the desired optical surface structure of the lens, such as a multifocal diffractive zone plate 18. The embossing surface 56 of the stamping die 54 is forced into engagement with the surface of the lens blank 30 at a predetermined stamping pressure and for a predetermined stamping dwell time. Sufficient heat or ultrasonic energy is applied to the lens generation area 31 of the lens blank 30 to heat the lens generation area to a temperature between the glass transition temperature and the melt temperature of the polymer, and emboss the surface structure onto the lens generation area, The embossing surface 56 of the stamping die 54 is removed from the lens blank 30 following the expiration of the stamping dwell time.
Minnesota Mining And Manufacturing Company
Smart & Biggar
LandOfFree
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