Cathode ray tube device with improved color filtering system

A cathode-ray tube device for generating a bright light spot comprising:

• a cathode-ray tube including an evacuated envelope, means located within said envelope to generate an electron beam, a phosphor capable of emitting visible light radiation when excited by electrons, positioned within said envelope and in the path of said electron beam, and a transparent face plate forming part of said envelope and situated in the path of said visible light radiation and, positioned outside of the outer surface of said face plate and in the path of said visible light radiation, a light beam filtering means comprising, in a container which at least in the path of said light radiation, is transparent to said radiation and which comprises as a visible light radiation exit member a glass end plate, a light filtering solution containing in addition to light filtering ingredients, as index of refraction raising ingredients, a compound selected from the group consisting of cinnamic alcohol and cinnamaldehyde and mixtures thereof in an amount sufficient to form a concentrated solution thereof.