US Patent 7637604 Ink-jet printing process and ink-jet inks used therein

The present invention relates to an improved process for wet-on-wet ink-jet printing. This invention provides a progressive dot printing ink-jet process comprising the steps of applying a first ink drop to a substrate and subsequently applying a second ink drop on to the first ink drop without intermediate solidification of the first ink drop. The first and second ink drops have a different viscosity, surface tension or curing speed. Further ink drops may be applied sequentially to the combined first and second ink drops without intermediate solidification of the first and subsequent ink drops.