Electrolyte for an electrochromic display and an electrochromic display cell comprising this electrolyte.

摘要

There is disclosed an electrolyte for an electrochromic display of the kind in which a persistent coloured species of an electrochromic substance in solution is deposited onto a display electrode upon the passage of current therethrough. The electrolyte comprises an aqueous solution of a di-alkyl bipyridinium salt and a non-polymeric aliphatic alcohol in which either: (a) both alkyl groups of the bipyridinium salt have an odd number of carbon atoms and the alcohol has an even number of carbon atoms; or (b) both alkyl groups of the bipyridinium salt are have an even number of carbon atoms and the alcohol has an odd number of carbon atoms.

The alcohol inhibits recrystallisation (spotting) and non-erasure of the display electrodes. Particularly effective for 1,1' di-heptyl 4,4' bipyridinium dibromide, which has a severe lifetime problem, is n-hexanol.