The Research On Dot Gain In Ink-jet Printing

The three central factors influencing the quality of ink-jet prints are printing engine, inks and substrates. The emphases in this thesis are the last two factors, especially the interactive between inks and substrates including ink penetration and ink spreading. Before studying the interactive between inks and paper, the ink-jet printing technology and the materials of ink-jet printing are introduced, and also is the halftone method in ink-jet printing, ie. FM Screening. In the third chapter the optical dot gain is analyzed deeply. The optical dot gain results from basically the light scattering in substrates. In ink-jet printing the ink penetration changes the optics of the coating of the substrates including the light scattering coefficient and absorption coefficient. So it affects the optical dot gain greatly. The application of Kubelka-Munk (K-M) Theory in halftones is also studied, and so an ink penetration model is established using K-M theory. The penetration depth and the scattering and absorption coefficients are decided. According to the prediction results of reflectance using K-M theory we can see that the ink penetration changes the hue of the color, the color saturation and reduces the range of tones of the prints. Then another interactive between ink and paper–ink spreading is analyzed. First the dynamitic process of ink spreading is illustrated. And on the basis of fractal theory an ink-spreading model is put forwarded. In the last chapter 125 test samples are designed to confirm the two models above. The results proved that when predicting the color of prints the consideration of ink penetration and ink spreading would improve the accuracy of prediction comparing with measurement.