US Patent 11609470 Writing device including cholesteric liquid crystal and having sectional erase

A writing device includes a liquid crystal layer including reflective cholesteric liquid crystal material. There are electrically conductive layers between which the liquid crystal layer is disposed. At least one of the electrically conductive layers includes at least two conductive sections. There is a front substrate that is flexible and a back substrate between which the electrically conductive layers and the liquid crystal layer are disposed. Neither the front substrate nor the back substrate includes separated sections. Application of pressure to the front substrate changes a reflectivity of a portion of the cholesteric liquid crystal material to form an image. In one aspect, there is electronic erase circuitry including at least one actuator that independently applies an erase voltage waveform to each of at least two of the conductive sections. In another aspect the electronic erase circuitry includes at least one actuator that independently applies an erase voltage waveform to each of the conductive sections, and that applies erase voltage waveforms to at least two of the conductive sections in combination.