Abstract
Electrolytic printing ink has been developed based on a polymeric gel. This polymeric gel ink consists of poly(vinyl alcoho1)(PVA)partially crosslinked with borax, carbon black as a pigment, and water. It has the nature of gel to sol transition with pH variation. During to the transition its viscosity decreased.
There are several techniques to change pH such as the addition of acidic or alkali and the application of electric voltage. However, adding chemical substances changes the composition of the gel ink. Consequently, electric voltage was chosen to vary pH. When the electric voltage was applied to the gel ink, an electrochemical reaction occured on the gel ink so that pH became acidic at the anode and viscosity of the gel ink was reduced enough to adhere to a paper. Application of rectangular pulse voltage caused the same phenomenon as a constant voltage.
A Printing apparatus was also designed. Polymeric gel ink with electric conductivity 4.0 × 10-3 Ω-1cm-1 was used. The gel ink was coated on the surface of a metal roller. Then an electric voltage was applied to it by electrodes corresponding to picture elements. Image pattern was formed on the surface of the gel ink and then it was definitively transferred to a paper. When electric voltage was not applied to it, the surface did not show any change.
Polymeric gel ink could offer resolution of at least 200 dots per inch (dpi). Image density was fully controllable from 0.05 to 1.5 as optical density by application of an electric voltage of 3-12 V. Printing speed was 22mm/sec.. An advantage of this printing system is that the polymeric gel ink not only acts as an ink but also as the support and the carrier of the ink itself.
