4 thereon of a material such as for example tin oxide the pattern may be etched on the substrate by using a commercially available material known as nesa glass and removing the conductive coating except for electrodes 3 4 coated on transparent electrode segments 3 4 are layers of electrochromic material such as tungsten trioxide wo 3 indicated as 11 12 the electrochromic layers 11 12 are applied by suitable masking techniques to cover a smaller area than the electrodes so as to give good edge definition substrate 2 may be made of glass ceramic plastic or preferably metal such as tungsten and includes counter electrode 9 the composition and formation of which are described in detail hereinbelow as shown terminal 10 connects counter electrode 9 to the electrical circuitry of the display electrolyte layer 15 may take various forms but a preferred electrolyte having optimized cationic mobility comprises acidified aqueous solutions for example an aqueous solution of sulfuric acid or phosphoric acid in which the acid content ranges from about 5 to 80 by volume dilute acid solutions are preferred since they provide increased cationic mobility h mobility for coloration purposes although less preferred aprotic and solid state electrolytes may also find use in the.