In order to rival the quality of silver halide photographs, digital printing systems need to satisfy issues of high print quality as well as image stability. Our research and development efforts have focused on thermal dye transfer and ink jet printing systems, with extraordinarily good results in each system.Discussion will focus on the chelate reaction between dye molecules and metal ions in the thermal dye transfer printing system, which has greatly improved the image stability issues, well in excess of original targets.As for ink jet printing, attention was paid to improving the print quality. These efforts led to the world's first production of micro porous printing media with an RC-paper base. The combination of the printing media and dye inks brings the expected print quality together with other features such as quick drying cased by high ink-absorption speed, resistance to water.Work on improving image stability in ink jet systems will also be discussed.