GB803019A - Method of preparing a fluorescent screen and a fluorescent screen when prepared by the method - Google Patents

Abstract

803,019. Luminescent screens. SYLVANIA ELECTRIC PRODUCTS, Inc. March 10, 1955 [March 24, 1954], No. 7097/55. Class 39(1). Method of preparing a fluorescent screen for a colour television tube includes the steps of coating a glass or other plate 12 of the screen with a tacky material 14, arranging a mask 10 of conductive material having apertures 20 in spaced relation, by the annular member 36, with the coated plate, introducing a quantity of a colour-emitting phosphor 18 into a region opposite the coated plate and separated therefrom by the apertured mask and electrostatically charging the phosphor in a field arranged between the apertured mask and a conductive plate 16 to cause the phosphor particles to migrate through the apertures 20 and to be deposited on areas of the plate 12, 14 which are exposed by the apertured mask. Second and third colour emitting phosphors can be deposited on other areas of the plate 12, 14 by indexing the mask 10 with respect to the plate 12 or by using differently apertured masks, the additional phosphors being placed in turn on the plate 16 or fresh plates 16 with the additional phosphors being used. Alternatively the operations can be carried out at three stations, the glass plate 12 being carried to each station in turn. The phosphor can be deposited on the plate 16 by blowing a charge through the tube 40. A screen 30 can be positioned between the plate 16 and the mask 10 to break up or intercept lumps of phosphor and can be in the form of a wire mesh having 325 holes to the inch. The plate 16 can be made of aluminium or graphite and annular spacing members 32 and 34 of "Bakelite" (Registered Trade Mark). The distance between the mask 10 and the plate 16 can be about “ inch with a potential difference of about 7-10 KV between them. The tacky material 14 can be silicone grease, phosphoric acid deposited as smoke on moist glass or moistened with water vapour, potassium or sodium silicate, or nitro-cellulose lacquers. After the phosphor screen has been formed the tacky material can be baked-out or otherwise removed. In the embodiment illustrated in Fig. 3 a dished face-plate 50 of a C.R.T. and a correspondingly dished mask 52 are used.