Abstract
A tungsten-oxide single-layer film can be colored densely by using dilute sulfuric acid as a liquid electrolyte instead of the multilayer electrochromic cell. The transmissivity contrast before and after coloration reaches 70% at a wavelength of 405 nm. The bleaching relaxation time of a colored tungsten-oxide single-layer film is in the order of 1000 hours and depends on the sputtering power.