Ink-jet printing technology on maunfacturing color filter for liquid crystal display - Part I: Ink-jet manufacturing processes

A manufacturing process is developed to make color filter by discharging the predetermined color ink to the substrate, and then curing the discharged ink to form the color filter pattern. In this paper, an ink-jet printing apparatus with drop on demand multi-nozzle heads was set up to manufacture color filters. The apparatus includes a X-Y-theta table supporting the substrate, and a set of drop-on-demand ink-jet heads arranged on the adjustable Z-axis for coloring the filter elements. The special inks invested by ITRI (Industrial Technology Research Institute, Taiwan), by using this system with OES self developed print head, a strip-type color filter (pixel size 113 mum * 339 mum, with 20 mum black matrix width) made by ink-jet printing method is achieved. The color coordinates of three colors (red, green and blue) on the chromaticity diagram are (0.64, 0.35), (0.31, 0.52) and (0.13, 0.13). The transmittance for red, green and blue is 90%, 80%, and 85%, respectively. Compare with commercial standard, the heat, light and chemical test results come to DeltaE <5 for each color, but the alkali tests (5% NaOH & KOH) are not satisfactory. Further study to improve the ink formula is needed.