Prodn. of light impervious layer around edges of lens - by coating with blackening agent and microwave heat-treating to remove any air pockets

摘要

Method of producing a light impervious layer around the edges of a lens consists of coating the edges with a blackening agent followed by heat treating with microwave radiation. This treatment melts the agent and then rehardens it or burns it into the surface. The lens moves through an area (5) in which a microwave field (6) produces a predetermined thermal gradient. The agent is an organic powder, a lacquer, esp. a water soluble lacquer, a paint, a paste material or a foil. ADVANTAGE - Avoids the presence of air pocket between the lens surface and blackening agent without introducing surface stresses which could later lead to the destruction of the optical properties.