Method of forming fluorescent screens of color picture tubes

A method of forming a fluorescent screen of a color picture tube comprising the steps of:

• A. applying to the inner surface of a face plate of said tube a film comprising a mixture of a photosensitive binder selected from the group consisting of ammonium dichromate, a benzene chloride diazonium salt, and a diazo resin, and a photosensitive composition consisting essentially of a diazonium salt in a film-forming resin, said diazonium salt being capable of forming zinc chloride upon exposure to light;
• B. exposing to light a predetermined portion of said film to be deposited with phosphors thereby rendering sticky said portion by a photoreaction created by said light exposure of the photosensitive composition and moisture in atmosphere, and causing the photosensitive composition and photosensitive binder to undergo a cross-linkage reaction whereby the exposed area becomes insoluble in washing fluids;
• C. depositing a powder of phosphors onto said predetermined portion whereby the powder sticks thereto as a result of the photoreaction;
• and
• D. washing the deposited film with a member in which said exposed portion of film is insoluble, said member selected from the group consisting of water, organic solvents, mixtures thereof, and solutions of inorganic compounds, thereby removing the non-adhered phosphor powders from the non-exposed portions of the said film.