Colour photocopying:- Explained in brief
by : This blog is only for the information purpose.
Colour photocopying:-
In black and white photocopying the main pigment used is carbon black (C.I. Pigment Black 7). In colour reproduction the three pigments used, in addition to black, are either the same subtractive primaries i.e., yellow, magenta and cyan as used in conventional pronting, or red, green and blue. Pigments such as C.I. Pigment Yellow 1 (3), C.I. Pigment Red 2 (4), or C.I. Pigment Blue 15 (5) have been used. The pigmented developers are applied separately to the latent image in three stages corresponding to the yellow, magenta and cyan content of the original document.
More extended azo pigments, e.g., C.I. Pigment Yellow 97, quinacridones e.g., C.I. Red 22 or pigments based on perylene amides such as Pigment Red 149, have been assessed for this purpose. The induction of charge depends on the structure of thr pigment, its electrical resistivity and in some cases on its degree of crystallinity. Toners contaning thermochromic pigments are also claimed which provide images of varying intensity, depending on the temperature. One interesting application a computer designed print out can be colour photocopied using developers containing sublimable dyes. The photocopy can then the be transter printed onto fabric. The operation from computer input to finished sample for customer use can be achieved in 15 min.
