PURPOSE: To eliminate micro chips and cracks that could be generated in the edge portion of a front face panel or a back face panel constituting a vacuum envelope so as to enhance the mechanical strength of the vacuum envelope by providing a beveled portion at the edge portion of the front face panel or the back face panel.
CONSTITUTION: Beveled portions 15 having a radius of e.g. about 0.5mm are formed at the respective edge portions of a front face panel 2A and a back face panel 3A which constitute a vacuum envelope 1. The beveled portions 15 can be readily formed by cutting out from a large glass plate material glass plates of predetermined size for use as the panels 2A, 3A, and abrading the glass plates with sandpaper of e.g. No.600 Round curved surfaces are thereby formed at the respective edge portions of the panel 2A and the panel 3A and so distortion due to the cutting is reduced and micro chips or cracks are difficult to be generated even with stress application, whereby deterioration of the mechanical strength of the envelope 1 can surely be prevented. Therefore, a light-emitting element of high quality and reliability is provided while enhancing the productivity and safety thereof.
SEKO KOJI
KAMOGAWA YUJI
SHIMOJO TOKUHIDE
KANDA ISAMU
HARA ZENICHIRO
FUTAISHI SHUNICHI
SHIBAYAMA KOZABURO
MITSUBISHI ELECTRIC CORP