Method of forming phosphor pattern on fluorescent screen for color picture tubes with polymer coagulent

In a method of forming a fluorescent screen for a color picture tube comprising:

• a first step of coating an inner panel face of a bulb of the color picture tube with a photosticky substance mainly containing a diazonium compound to form a layer of the compound:
• a second step of exposing to light through a color selection electrode portions of said compound layer where a first color phosphor is to be adhered to as to render exposed portions of said compound sticky;
• a third step of applying the first color phosphor on the surface of said compound layer;
• a fourth step of removing surplus first color phosphor applied on unexposed portions of said compound layer;
• a fifth step of conducting said second, third and fourth steps consecutively for the phosphor of second and third colors to form a fluorescent screen comprising picture elements of triads of three color phosphors on the inner face of the panel;
• and
• a sixth step of filming or aluminizing said fluorescent screen;
• the improvement wherein after applying the three color phosphors to the inner face of the panel and before said filming or aluminizing step, said said inner panel face with picture elements of three color phosphors is treated with an aqueous solution of polymer coagulant to improve the adhesiveness of the phosphor to the inner panel face thereby allowing sufficient washing to form a color picture tube having better quality and improved brightness.