Digital and electronic inks

Digital and electronic inks

Non-impact printing (NIP) technology ('plateless printing') is becoming popular these days, with the proliferation of computers, office copiers, fax machines and laser printers, and home and office ink jet printers. By definition, NIP accepts electronic input (for example, digital) and uses 'impactless' electrostatic, dielectric inkjet, thermal transfer or magnetic printing technologies to put an image onto substrates. Digital printing is the merging of the graphic design system (scanner or computer) with the printing unit.
Inkjet technology is the fast growing segment in the NIP sector (Chem. Br., August 2000, p39). Here an electrical pulse forces the printer to eject an ink drop. The ink for this purpose has the same general composition as other inks, but has some special characteristics: for example, very small particle sizes are required to pass through the fine nozzle and very low viscosity is needed for free ink flow. Drop on Demand (DOD) and Continuous Ink Jet (CIJ) are the two main inkjet printing technologies. Piezo Ink Jet DOD technology, in which a piezo crystal pushes a drop of the ink when prompted by a frequency regulated energy impulse, dominates the market.
Electronic inks represent the latest development in inks that is expected to change the concept of printing itself. These inks are now used in sign boards, and the display can be changed electronically, without resorting to liquid crystal displays (LCDs) or light emitting diodes (LEDs). Electronic inks change colour when an electric field is applied to them. The ink is made up of tiny bubbles of a dark coloured dye in which light coloured particles are suspended. These plastic-encapsulated particles are printed on a conductive material and some look light and some look dark when electricity is applied, so creating images. Normally the ink is not visible and reveals images only on applying electricity. Microcapsules of proprietary particulate materials mixed with the appropriate binders form the main constituents of these inks.