Abstract: A liquid crystal device of the kind in which individually addressable regions are settable to different optical states in response to drive waveforms is described. The waveforms are used to cause the material in different regions to remain set in its existing optical state or to change to another state in dependence upon data to be input to the device, and they are pulse-like in nature and of predetermined amplitude and duration. The operating speed of the device in response to said waveform is improved by causing the profile of the waveforms to depart from the usual squared profile. In one example, the waveforms are caused to have substantially triangular leading and/or trailing edges and the profile causing the material to remain set in its existing optical state differs from that causing the material to change into another optical state.