Process for forming luminescent screens

Claim 1

IN THE PROCESS OF FORMING A LUMINESCENT SCREEN BY DEPOSITING THE LUMINESCENT MATERIAL FROM AN AQUEOUS SETTLING BED HAVINS A PH OF MORE THAN 9.5 AND CONTAINING SAID LUMINESCENT MATERIAL, A SILICATE SELECTED FROM THE GROUP CONSISTING OF POTASSIUM AND SODIUM SILICATE AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL AND ALKALINE EARTH COMPOUNDS OTER THAN SAID SILICATE ON A SURFACE THUS FORMING A LUMINESCENT SCREEN, AND THEN ADDING TO SAID SETTLING BED A SOLUTION OF AN ORGANIC FILM FORMING MATERIAL HAVING A SPECIFIC GRAVITY LOWER THAN THST OF THE SETTLING BED, AND REMOVING THE SETTLING BED TO FORM A THIN COHERENT ORGANIC FILM ON THE LUMINESCENT SCREEN, THE IMPROVEMENT WHICH COMPRISES REDUCING THE PH OF THE SETTLING BED TO A VALUE BETWEEN ABOUT 5 AND 8.5 BY THR ADDITION OF AN ACIDIC SUBSTANCE AFTER THE FORMATION OF THE LUMINESCENT SCREEN BUT BEFORE THE ORGANIC FILM FORMING MATERIAL IS ADDED TO THE SETTLING BED.