Abstract
Pulp fibers were dyed with direct dye in red and then the sheet was etched by sputtering. Change in color of the sheet was investigated in terms of differential metric lightness (ΔL*), differential metric chroma (ΔC*ab) and differential metric hue (ΔH*ab) parameters on the basis of CIE L*a*b* color system. All theses parameters relating to the color depth were changed with the sputtering conditions, especially gas pressure and sputtering energy. Sputtering at a gas pressure of 10 Pa gave a maximum color deepening up to ΔL* of -1 and ΔC*ab of +3 atthe sputtering energy of 20 J/cm2 with little change of ΔH*ab, which may be the best sputtering condition for color deepening. Sputtering at the gas pressure of 1 or 0.2 Pa showed the increase in minus ΔL* and plus ΔH*ab with an increase in sputtering energy, and gave maximum plus value in ΔC*ab around the sputtering energy of 100J/cm2. Color deepening by sputtering on chromatic -colored paper is attributed to the minus ΔL* and plus ΔC*ab, both of which were occurred simultaneously. The change, of color deepening with an increase in sputtering energy as shown in the colorimetric parameters were interpretted as a combination of color deepening and anti-color deepening occurred concurrently by sputtering. The former should be caused by the surface microstructure i. e. dense forests of cones or numerous microcraters and their prestructure, and the latter should be caused by thermal degradation of fiber and dye and by the etching of fiber surface layer which has an abundance of color dye.
