| 摘要 |
474,591. Glass manufacture. STANDARD TELEPHONES & CABLES, Ltd. June 25, 1937, No. 17724. Convention date, Aug. 27, 1936. [Class 56] [Also in Groups XL, XVI, and XXXVI] A dielectric element for use in a condenser, as an insulating support for material which emits secondary electrons or as the base plate of a mosaic screen in a cathode-ray tube, is formed of glass the centre 21 of which has been etched away until it is very thin but supported by the thicker edge or border 22. To form the plate a sheet of glass has its edge coated with beeswax and the centre treated' with hydrofluoric acid either on both sides or only on one side ; the treatment may be effected in stages 'with acid of varying concentration. A mixture of hydrofluoric acid, sulphuric acid and water may be used as the etching means with silver chloride or a mixture of silver chloride and iodide as the resist. |
