Abstract: The invention provides a protective and heat resisting membrane for application onto electrochromic layers and/or leads in an electrochromic display to prevent dissolution and erosion thereof as a result of contact with the display electrolyte. The membrane typically comprises (a) a long chain organic acid, preferably a water insoluble carboxylic acid, (b) optional acid reistant epoxy resin and (c) a compound selected from at least one of an amine and amide in sufficient amount to form the respective amino or amido salt of the acid, which salt together with any epoxy resin present, imparts water repellency and ionic conductivity to the membrane, and with the amine or amide being present in less than the amount required to fully cure any epoxy resin present with time and temperature so that only a minor, dispersed portion of the resin is cured. Curing of a minor, dispersed portion of the resin improves adherence and does not adversely affect the ionic conductivity of the membrane.

Abstract: Disclosed is an electrochromic display having an electrolyte of optimized cationic mobility and a counter electrode of optimized electronic mobility. Preferably the display comprises (a) a front substrate with selectively actuable transparent electrodes and image-forming electrochromic layers thereon, (b) an acidified aqueous electrolyte containing a sufficient quantity of highly mobile hydrogen ions for coloration of the electrochromic layers and (c) a rear substrate spaced from the front substrate carrying a counter electrode in contact with the electrolyte, the counter electrode being in the form of a layer comprising predominantly an alkali tungsten bronze, preferably sodium and or potassium tungsten bronze, in the high temperature heat treated condition which exhibits enhanced electronic mobility. A process for making the display is also disclosed.