Process for producing flat plate illumination devices

Abstract

A multistep process is disclosed which enables hermetically sealed, durable, long-lasting illumination devices which utilize electrical discharges through inert gas and inert gas/mercury vapor mixtures to be produced in an essentially flat-plate configuration without the use of glass tubing to contain the discharge. This process utilizes plates of glass having a particular range of thermal expansion coefficients for the preparation of these display devices through the discovery of a heating/cooling process that enables these thick glass assemblies to be produced rapidly yet without cracking and without significant residual air or water vapor contamination and which includes the heat sealing of a evacuation/backfilling tubulation in the same sequence and also includes the unique feature of the inclusion of finely divided powder in the inert gas chamber which, when subjected to the heating/cooling cycle, acts to getter residual air and water vapor from the inert gas. This process also utilizes a special means for preventing the adhesion of the flat plates to the platens used for their support during the thermal fusing treatment that is required to form the gas discharge channels. An interrupt step, introduced after fusion bonding is complete, enables the usage of a low softening point glass having a thermal expansion coefficient compatible with that of the window glass to produce the evacuation and gas filling tubulation port.