Electrochromic displays are very simple and cheap.
prelonic developed the probably cheapest EC display regarding materials and process. It could be printed fully and one-sided in a dry stack. The displays are characterized by low current and fast response at 1,3 Volts.
The printing process is simple: all layers are printed via simple standard screen printing. All materials are available on a commercial base.
The display could be used to show images or logos, but also variing information by using segmented displays.
The image display duration can be adjusted from fading out within few minutes to instantly disappearing image.