Abstract: A process for the deposition, on an optical substrate, of an antireflection coating capable of being engraved. In the process, metal is evaporated in a reactive atmosphere within the enclosure of an evaporator under vacuum and then deposited on the substrate. Previously cleaned substrates are disposed within the enclosure, which is then evacuated until a pressure of at most 1.5 .mu.Pa (10.sup.-8 torr) is obtained. Pure oxygen is injected at a regulated throughput in such a manner that the pressure is within the range of from 2 to 4 mPa, preferably 3 mPa (2.times.10.sup.-5 torr). A heated boat which is disposed within the enclosure and contains chromium is unmasked. The chromium evaporates at a temperature such that a coating of chromium oxide grows in thickness on the substrates at a rate of 0.1 to 0.5 nm per second, preferably 0.2 nm per second.

Abstract: A plastics container with a lid having a skirt extending downwardly around the upper edge portion of the container, the lower edge of the skirt being covered by a protecting member connected with the outer side of the container wall, the protecting member having a vertical flange provided at its upper edge with an inner bead which in the closed position of the lid engages with an outer bead on the skirt at the lower edge thereof.Such arrangement improves upon resistance against disengagement of the lid from the container in the case of elevated pressure in the container or strong deformation of the container.