GB523848A - Improvements in and relating to electric discharge lamps - Google Patents

Abstract

523,848. Glass manufacture. BRITISH THOMSON-HOUSTON CO., Ltd., SCOTT, W. J., ANDERSON, J. T., and WELLS, R.S. Jan. 16, 1939, No. 1474. [Class 56] [Also in Group XL] In an electric discharge lamp wherein a layer of fluorescent material is attached to the inside of the glass envelope, a protective coating of an ultra-violet-transmitting, gas permeable glaze is applied to the material; the fluorescent material may be mounted by direct dusting or with a binder such as enamel, boric acid, phosphoric acid, the silicon ester preparation described in Specification 494,105, [Group XV], or by the method described in Specification 523,528, [Group XL], as a suspension in an organic medium. After coating, the fluorescent material is baked on. and at least part of the suspension medium thereby removed ; one or more layers of glass as a suspension in an organic medium is then applied and the tube, is then baked to remove all remaining organic medium and to cause the glass to fuse together and form a porous layer. As a result in the subsequent degassing, gases from the envelope can readily escape and not harm the fluorescent material. To the glass in suspension as described above may be added a small proportion of glass particles having a different coefficient of expansion than that of the main glass coating material, so that cracks will be obtained in the surface when the process has been completed. Reference has been directed by the Comptroller to Specification 512,308.