Patent GB-1350667-A (GB)
Title: Method of making colour screens
IPC: H01J9/227
Filed: 1971-07-08
Abstract: 1350667 Luminescent screens SONY CORP 8 July 1971 [11 July 1970] 32205/71 Heading H1D The manufacture of a colour screen for a colour picture tube having a shadow mask wherein the screen including a light absorbing layer with holes of diameter less than that of the shadow mask apertures comprises applying a photoresist layer, irradiating with light from point or extended source through the mask, developing to form a plurality of resist dots, forming a light absorbing layer on the entire face, and removing said dots to leave an apertured light absorbing layer, characterized in that the light source is moved in a circle in turn about the axes corresponding to the red, green and blue phosphor systems respectively. The photoresist material may be rendered insoluble when exposed to light and the circle radius r may be 0 < r <#/#-1.a where # is the ratio of the light source to face spacing to light source to mask spacing and a is the aperture radius. When the resist is rendered soluble by light, the circle radius r < #/#-1.a. The latter forms annular exposed regions with inner diameters (e.g. 280Á) smaller than the mask apertures of 380Á diameter. Initially (Figs. 4A-4J, not shown) continuous positive resist layer (11) is laid, exposed rings (13G) formed about areas (12G) for green phosphor occupation, corresponding (13B), (13R) regions formed, exposed areas removed by alkaline solution, and graphite layer (15) added. The resist sensitization is inverted trapezoid due to increase of light absorption with depth, sharp edges (14a) ensuring accuracy. Then light irradiates the outer face to sensitize regions (14), the layer developed by alkaline solution to remove regions (14) and associated graphite (15A) producing light absorbing regions at areas not to be occupied by the phosphors. The phosphors are deposited by resist slurries, Al film (22) formed through intermediate film (21) of acrylate resin then removed by baking. Larger green phosphor dots to compensate for lower brightness may be provided by increasing the gyration radius. With a negative resist and r < #/#-1.a, formation is as in Figs. 5A to 5J, (not shown) producing resist areas (33) after water development at areas to be phosphor occupied, covering with graphite (34) and hydrogen peroxide developed to remove areas (33) and associated graphite coverings, and photosensitive slurries utilized to provide phosphors (37R), (37G), (37B). Similarly, one set of phosphors may be of greater area than the others. Fig. 6 (not shown) illustrates a rotary lamp source with lamp house (40) enclosing point or extended light (41) (e.g. super high pressure Hg arc lamp), shift means (43) rotating support (42) and sliding same in x-y direction by micrometers (50) and (51), means (43) being mounted on rotary unit (45) rotatable on fixed shaft (44) and with pulley (47<SP>1</SP>) driven by synchronous motor (46). Second shift means (53) moves fixed shaft (44) in the x and y directions by micrometers (55), (56). Inlet and outlet pipes (57) and (58) discharge cooling water. Shift means (60) effects repositioning for the different phosphors, while reference numeral (61) indicates a correcting lens.