Scan driving method for high-quality image and cholesteric liquid-crystal display device using the same
A display device is provided, which includes a display panel. The display panel includes a first substrate, a second substrate, a cholesteric liquid-crystal (ChLC) layer, and a driving circuit section. A plurality of first electrodes formed on the first substrate extend in a first direction. A plurality of second electrodes formed on the second substrate extend in a second direction different from the first direction. The ChLC layer is formed between the first substrate and the second substrate. The driving circuit section is configured to apply a plurality of alternating-current (AC) voltage pulses to pixel circuits at intersections between the first electrodes and the second electrodes. The driving circuit section is further configured to perform a full screen reset procedure to the display panel followed by a pulse-width modulation (PWM) scanning procedure to control cholesteric molecules within the pixel circuits to enter a focal conic state.
1 . A display device, comprising:
a display panel, comprising:
a first substrate on which a plurality of first electrodes extending in a first direction are formed;
a second substrate on which a plurality of second electrodes extending in a second direction different from the first direction are formed;
a cholesteric liquid-crystal layer formed between the first substrate and the second substrate; and
a driving circuit section, configured to apply a plurality of alternating-current (AC) voltage pulses to pixel circuits at intersections between the first electrodes and the second electrodes,
wherein the driving circuit section is further configured to perform a full screen reset procedure to the display panel, which is followed by a pulse-width modulation (PWM) scanning procedure, to control cholesteric molecules within the pixel circuits to enter a focal conic state, wherein:
the full screen reset procedure comprises a first reset phase and a second reset phase arranged in sequence;
the cholesteric molecules within the pixel circuits enter a homeotropic state during the first reset phase, and enter the focal conic state during the second reset phase;
a plurality of first AC voltage pulses with a first voltage amplitude are applied to the pixel circuits during the first reset phase; and
a differential voltage sensed by the cholesteric molecules within the cholesteric liquid-crystal layer at an end of the first reset phase equals to a positive first voltage with the first voltage amplitude.
2 . The display device of claim 1 , wherein a first duration of the first reset phase and a second duration of the second reset phase are between 10 ms and 490 ms.
3 . The display device of claim 1 , wherein the driving circuit section gradually decreases the differential voltage sensed by the cholesteric molecules within the pixel circuits gradually from the positive first voltage to OV during the second reset phase.
4 . A scan driving method for use in a cholesteric liquid-crystal display device, the method comprising:
performing a full screen reset procedure to the cholesteric liquid-crystal display device to control cholesteric molecules within pixel circuits of the cholesteric liquid-crystal display device to enter a focal conic state;
performing a pulse-width modulation (PWM) scanning procedure, which follows the full screen reset procedure, on the cholesteric liquid-crystal display device to render an image on the cholesteric liquid-crystal display device, wherein the full screen reset procedure comprises a first reset phase and a second reset phase arranged in sequence;
controlling the cholesteric molecules within the cholesteric liquid-crystal display device to enter a homeotropic state during the first reset phase, and to enter the focal conic state during the second reset phase; and
applying a plurality of first AC voltage pulses with a first voltage amplitude to the pixel circuits during the first reset phase,
wherein a differential voltage sensed by the cholesteric molecules within the pixel circuits at an end of the first reset phase equals to a positive first voltage with the first voltage amplitude.
5 . The method of claim 4 , wherein a first duration of the first reset phase and a second duration of the second reset phase are between 10 ms and 490 ms.
6 . The method of claim 4 , further comprising: gradually decreasing the differential voltage sensed by the cholesteric molecules within the pixel circuits from the positive first voltage to OV during the second reset phase.