or preventing a u03c0 merisation of the aromatic moieties application_number US 92645810 A description reference will now be made in detail to the preferred embodiments of the present invention examples of which are illustrated in the accompanying drawing fig1 is a perspective view of a working cell for an electrochromic display the working cell for the electrochromic display is made by placing an electrochromic material between two transparent electrodes potentially indium tin oxide better known as ito electrodes the coloring of the electrochromic material is caused by changing the potential of the cell by charging the transparent electrodes the electrodes and the electrochromic mixture are sandwiched between a pair of substrates perhaps glass substrates in a preferred embodiment the value of the index n is in the range from 5 to 300 the new color is probably achieved by prevention of the stacking of the 4 4 u2032 bipyridine units which is also referred to as u03c0 merization and this allows the dye to switch to a bright blue in this case the hydroxyl functionalities block the stacking to u03c0 mers it is a further advantage of the formulation comprising the novel dye that the dye in its formulation in the display by virtue of the substituent effects has very rapid switch on and switch off performance in the range of 60 100 ms usually in the range from 0 5 to 2 seconds at the same time the substituent effects in the switched state also increase the color depth as a result of which a higher contrast can be achieved at a lower power consumption the new type of viologen dyes therefore.