Method of manufacturing color picture tubes

In a method of manufacturing a colour picture tube of the type comprising the steps of coating phosphors of three primary colours on the inner surface of the face plate of the colour picture tube to form dots or stripes of the phosphors;

• applying an acrylic resin emulsion on said dots or stripes of the phosphors to form an acrylic resin film;
• vapour depositing metal onto said film to form a metallic reflecting film;
• subjecting said acrylic resin film to a pyrolysis for decomposing it into gases;
• and removing the gases;
• the improvement wherein said acrylic resin film-forming emulsion consists essentially of a mixture of a plurality of film-forming emulsions each consisting essentially of a different acrylic resin having a different pyrolysis characteristic, wherein one of the emulsions of said mixture consists essentially of a first film-formimg acrylic polymer having a peak pyrolysis temperature lower than that of a second acrylic film-forming polymer contained in a second emulsion of said mixture and said first polymer is present in an amount of 5 to 40% by weight based on the total weight of said film-forming polymers, whereby said mixture results in an acrylic film-forming emulsion the film formed by which has a pyrolysis characteristic that is different from the pyrolysis characteristic of that formed by any of the emulsions forming said mixture.