Glass plate for visual display indicators - is made extremely flat by applying pressure during stress relieving heat treatment

摘要

The glass is laid on a flat template and pressure applied so the glass is in contact with the template. The glass plate is then heated to below its softening temp. and allowed to cool. The glass plate is pref. forced against the template by atmospheric press. due to the application of a vacuum via holes in the template. The glass thus obtd. can be used for image reproduction e.g. liq. crystal displays a flatness tolerance of e.g. 1 um being achieved.