The effect of ultrafine pigment color filters on cathode ray tube brightness, contrast, and color purity

A high brightness, high contrast, and high color purity cathode ray tube (CRT) has been realized by the application of a color filter of inorganic ultrafine pigment placed between the phosphors and the panel glass. The picture image contrast of the CRT is improved by the reduction of the diffuse reflection of ambient light at the tube face. To lower reflected ambient light, a pigmented phosphor or a low transmittance glass is commonly used. Although the first method has the advantage of raising color purity to a certain extent, both methods (pigmented phosphor and low transmittance panel) lower brightness. However, as the color filters are transparent to the phosphor light and absorb the rest of the visible spectrum, application of color filters improves both contrast and color purity without lowering brightness. Brightness increases 30% when the contrast remains the same and contrast increases 30% when the brightness remains the same. Chromaticity coordinates x/y (color point) is shifted from reddish orange to red and the color gamut (color reproduction area) expands by 10%.