5-2
Phaser 440 Color Printer
5
Theory of Operation
Print engine
Sublimation dye transfer — the engine's printing technology
To make colored prints, the print engine uses a color printing method called
sequential sublimation dye transfer printing
. Simply said, the print engine prints by
subliming or vaporizing dots of colored dye from a Mylar® ribbon into a sheet
of paper. The benefits of this method are high-resolution, continuous tone
printing, easy maintenance, and fast printing.
The print process
Figure 5-2 illustrates the printing process employed by the print engine. In the
printing process, a single piece of coated paper (or transparency film) is drawn
past a thin Mylar ribbon, called a transfer roll, which is coated with sequential
bands of colored dye: yellow, magenta and cyan and, in the case of 4-Color
Transfer Rolls, black. A heating device, called a thermal head, vaporizes the
colored wax from the transfer roll into the paper. The thermal head is an
electrical device containing 2816 individually controlled heating elements
aligned parallel to the short axis of the paper it prints upon. And because the
row of thermal elements span the width of the page, the print engine prints an
entire line at one time; this accounts for the print engine's fast print time. The
printer uses a special paper which presents an ultra-smooth, flat surface for the
dye to absorb into.
During printing, the print engine moves the paper past the thermal head three
times when a 3-color transfer roll is used (or four times for 4-color transfer rolls).
During each pass of the paper, individual thermal head elements sublime tiny
dots of dye from the transfer roll's colored bands; first from the yellow band,
then the magenta band, and finally, cyan. (For 4-Color Transfer Rolls, black is
transferred last, after cyan.) The overlaid colors combine on the paper to
produce a complete color image. After the three passes, the finished copy is
ejected from the printer. The dye transfer roll is supplied on one spool, feeds
past the thermal head and drum for printing, and collects on a take-up spool.
