Non-settling process for coating a phosphor slurry on the inner surface

Abstract

This disclosure depicts a non-settling process for forming on an inner viewing surface of a color cathode ray tube faceplate, a coating of an aqueous slurry composed of an organic binder and a suspension of particulate phosphor material of distributed particle size, which coating exhibits an extraordinarily suppressed radial streaking, a high degree of coating weight uniformity, and a predictable particle size distribution. The process comprises supporting the faceplate such that the central axis of the faceplate has a substantial horizontal component and slowly rotating the faceplate about the central axis thereof while dispensing a stream of phosphor slurry having a predetermined phosphor particle size distribution onto the central region of the faceplate inner surface, preferably substantially at the axis of rotation, such that due to gravitational forces and the slow rotation of the faceplate through the descending slurry stream, the slurry is suffused to the perimeter of the faceplate inner surface without any significant settling out of the phosphor particles onto the faceplate. The coating is then levigated by rotating the coated faceplate at a moderate angular velocity for a brief time interval, the joint effect of which moderate angular velocity and brief time interval being to level the coating down to a predetermined thickness while suppressing the formation of radial streaks in the coating radially outward of irregularities in or on the faceplate inner surface.