Photoresist for cathode ray tubes that includes vinyl

Abstract

The inner surface of a video display panel such as cathode ray tube (CRT) glass faceplate is initially coated with a mixture of one of the primary color phosphors, an organic binder such as polyvinyl alcohol (PVA) diluted with water, and a photoresist agent. The organic binder overcomes the poor adhesion to the glass faceplate of the photoresist which typically includes polyvinyl pyrrolidone (PVP) and reduces the oxygen which decreases phosphor exposure time. To overcome PVA and PVP incompatibilities which give rise to nonuniform film thickness, a vinyl pyrrolidone-vinyl alcohol (VP-VA) copolymer is added to the phosphor, organic binder and photoresist mixture in the range of 0.1-30 wt %. The copolymer with both the VP and VA functioning groups serves as a coupling agent between the PVA and PVP and eliminates incompatibilities between these components. The VP-VA copolymer preferably has a VP/VA mole ratio in the range of 20/80 to 80/20. The photoresist further includes a photosensitive tetraalkylammonium salt and water. By substituting the sodium disulfonate group in the prior an disodium salt with a di-tetraalkylammonium group, the water solubility of the salt is substantially increased permitting increased concentrations of the tetraalkylammonium salt to be used in the photoresist for improved video image contrast. The tetraalkylammonium salt also serves as a linking, or bonding, agent between VP-VA and PVP to prevent the VP-VA from being wiped away during CRT manufacture and for improved application of the photoresist to the glass faceplate.