Abstract
Generally, natural dyes have moderate colors and are environmentally friendly, but harmful mordants must be used for fixing them and obtaining a full color range on fabric, and it is very hard to improve K/S values of the dyeing, though we have tried repeated dyeings and mordanting. In this study, to give deep and strong colors on natural dyed fabrics, wool, silk and nylon 6 fabrics were dyed with several natural dyes, cochineal, curcuma longa L. and logwood, and then, they were treated by sputter etching. The apparent color depth (K/S) value of dyed fabrics was considerably increased with sputter etching time. SEM photographs showed that innumerable fine microcraters were shown on the fiber surface of wool, silk and nylon 6 fabrics by means of sputter etching treatment. This surface irregularity caused by sputter etching decreases the amount of light reflected, increasing the depth of shade considerably. The color change effect of sputter etching treatment on the dyed fabrics was evaluated by the CIELAB color system. ${\Delta}E^*$(color difference) was remarkably increased, while h (metric hue angle) was little influenced by sputter etching. Changes in $L^*$ (metric lightness) and $C^*$ (metric chroma) of dyed fabrics with various sputter etching time were different in accordance with the types of each natural dyes and mordants. Much importance should be given to the fact that $L^*$ for cochineal and logwood dyed was decreased, but $C^*$ for all three natural dyes was increased. Thus, sputter etching treatment is the very effective method to produce more vivid colors on dyed fabrics.