Optical filter in fluorescent liquid crystal display devices

A fluorescent liquid crystal display having a display side and a rear side comprising:

• a pair of substrates including a rear substrate and a display side substrate;
• liquid crystal material interposed between said pair of substrates;
• a fluorescent material mixed within said liquid crystal material for producing fluorescence;
• an exciting source at said rear side of said display for emitting exciting radiation to stimulate the fluorescent material to produce said fluorescence;
• a diffusing plate interposed between the exciting source and said rear substrate;
• the wavelength of the fluorescence being different from the wavelength of the exciting radiation, the fluorescent material having a high absorption coefficient with respect to the exciting radiation;
• first filter means between said diffusing plate and said rear substrate for controlling the propagation of the exciting radiation from said rear side to said display, said first filter means permitting the exciting radiation capable of being absorbed by the fluorescent material to pass therethrough and preventing the exciting radiation having a wavelength which is substantially equal to the wavelength of the fluorescence from passing therethrough and preventing said fluorescence from passing therethrough to said rear side of said liquid crystal display;
• and
• second filter means adjacent said display side substrate for permitting passage of said fluorescence therethrough and for preventing the exciting radiation not absorbed by said fluorescent material from passing therethrough.