GB1325953A - Method of manufacture of colour cathode ray tube screens - Google Patents

Abstract

1325953 Colour television tubes ZENITH RADIO CORP 2 June 1971 [24 Aug 1970] 18598/71 Heading H1D In the manufacture of a multi-dot or like colour screen wherein each phosphor element is deposited over a filter element which transmits the colour emitted by the phosphor, the filter elements are deposited by a photo-resist process and comprise an inorganic colourant derived by heating an organic metallic compound. In one process the screen is coated with the organic compound, which is insoluble in water, coated in turn with a water soluble resist, such as polyvinul alcohol sensitized with ammonium dichromate, (Fig. 3, not shown). The photo-resist is exposed through a shadow mask and developed to leave a dot pattern of the resist over a continuous layer of the organic compound (Fig. 4, not shown) and the screen is then washed with a solvent which removes exposed areas of the organic compound (Fig. 5, not shown). A heating step converts the remaining organic compound dots into dots of filter material and may be carried out at this stage, or alternatively after all three filter patterns have been deposited in like manner, or alternatively as a final step when all the filters and phosphors have been deposited. Preferably the three sets of filters are deposited first and then the overlying phosphors are deposited on them by a photo-resist process. As an alternative, phosphor material may be included in the photo-resist coating which is used to form the filter pattern so that the filter and phosphor materials are deposited simultaneously. In an alternative process the organic metallic compound is mixed with an organic based photosensitive polymer to form a single coating which is exposed and developed to form a dot pattern (Fig. 7, not shown). The organic metallic compounds are preferably metallic lustres, that is metal resinates which are the reaction products of metal compounds or oxides as a base neutralized with an organic resinic acid. Gold with no oxide additive develops a reddish colourant, chrome oxide results in a green tint, and cobalt oxide blue. The edges of the filter dots may overlap to form opaque areas between each light transmission area (Fig. 1, not shown).