ANTISTATIC POLYMER LAYERS BASED ON POLY(ISOTHIANAPHTHENE) APPLIED FROM AQUEOUS COMPOSITIONS

Abstract

Electrostatic charging of photographic materials can be avoided by applying an antistatic coating to one or both sides of the photographic film. Electronically conducting polymers can be used for this application especially because the conductivity is independent from the relative humidity. However, these polymers usually are deeply coloured. It has been suggested that the absorption of polyisothianaphthene in the visible part of the spectrum is low, due to its low energy band gap. Application of polyisothianaphthene, however, is difficult due to its insolubility. A method is provided wherein an antistatic layer of polyisothanaphthene is coated from an aqueous dispersion. In this method polyisothianaphthene is polymerised in concentrated sulphuric acid and dispersed in water with the help of lambda carrageenan as a polymeric surfactant. Coating from this dispersion on a polyethylene terephthalate substrate yields a transparent antistatic film whose logarithm of the surface resistivity is 8.48 OMEGA/Square.