Driving device and method for matrix-type display panel using guest-host type phase transition liquid crystal

An apparatus for driving a guest-host phase transition liquid crystal in matrix comprising:

• (a) a plurality of liquid crystal display elements including a guest-host liquid crystal with a pleochroic dye added to one of the cholesteric-nematic liquid crystal and the chiralnematic phase transition liquid crystal, said liquid crystal display elements being driven by X and Y electrodes arranged in matrix,
• (b) a circuit generating a rectangular wave clock signal,
• (c) a drive waveform generator circuit for generating in synchronism with said rectangular wave clock signal an X electrode non-selecting voltage and an X electrode selecting voltage to be applied to said X electrodes and a Y electrode non-selecting voltage and a Y electrode selecting voltage to be applied to said Y electrodes, in order to supply each liquid crystal cell of said liquid crystal display elements with selected one of a holding voltage for holding the display condition and a write-in voltage for new writing operation, said drive waveform generator circuit further generating in synchronism with said rectangular wave clock signal an erasure holding voltage to be applied to one of said X and Y electrodes, said holding voltage being selected to be applied to the liquid crystal cells other than those liquid crystal cells to be erased when substantially the same waveform voltage is applied to the X and Y electrodes corresponding to the liquid crystal cells to be erased, in order to apply an erasure voltage to each liquid crystal cell positioned at the parts to be erased,
• (d) an X electrode driving circuit for supplying each of said X electrodes of said liquid crystal display elements with at least the X electrode non-selecting voltage and the X electrode selecting voltage selectively amoung the drive waveform voltages derived from said drive waveform generator circuit,
• (e) a Y electrode driving circuit for supplying each of said Y electrodes of said liquid crystal display elements with at least the Y electrode non-selecting voltage and the Y electrode selecting voltage selectively among the drive waveform voltages derived from said drive waveform generator circuit,
• (f) a change-over circuit for enabling the X electrode non-selecting voltage and the X electrode selecting voltage to be applied to said X electrode drive circuit and the Y electrode non-selecting voltage and the Y electrode selecting voltage to be applied to said Y electrode drive circuit at the time of execution of the writing operation, at least said X and Y electrode drive circuits being supplied with substantially the same waveform voltage while applying said erasure holding voltage to one of said X and Y drive circuits at the time of execution of the partial erasure,
• (g) a designating circuit for designating a region in the display panel of said liquid crystal display elements, where one of said write-in and partial erasure is to be executed, and
• (h) a control signal generator circuit for supplying a control signal to said X electrode drive circuit and said Y electrode drive circuit in such a manner that a write-in voltage is supplied to the liquid crystal cells to be written in the region designated by said designating circuit and a holding voltage is supplied to the other liquid crystal cells at the time of execution of the write-in operation, an erasure voltage being applied to the liquid crystal cells in the region designated by said designating circuit and a holding voltage being applied to the other liquid crystal cells at the time of execution of said partial erasure.