Liquid crystal display device, driving method of liquid crystal display device and electronic apparatus, having pixels with memory functions
View Patent ↗A liquid crystal display device in which pixels having a memory function are arranged includes: a display drive unit performing display driving by a driving method for obtaining halftone gray scales by setting plural frames as one cycle and temporarily changing gray scales of respective pixels within one cycle; and a pixel drive unit supplying a voltage having the same phase as, or the reverse phase to, a common voltage the polarity of which is inverted in a given cycle and applied to counter electrodes of liquid crystal capacitors to pixel electrodes of the liquid crystal capacitors. The pixel drive unit supplies an intermediate voltage between high- and low-voltage sides of the common voltage to the pixel electrodes of the liquid crystal capacitors at the time of transition from the supply of the voltage having the same phase to the supply of the voltage having reverse phase.
1. A liquid crystal display device in which pixels having a memory function are arranged, comprising:
pixel electrodes constituting the pixels arranged in a matrix;
counter electrodes disposed opposed to the pixel electrodes, liquid crystal capacitors of the pixel being formed between the pixel electrodes and the counter electrodes;
a display drive unit configured to perform display driving by a driving method for obtaining halftone gray scales by setting frames as one cycle and temporarily changing gray scales of respective pixels within one cycle; and
a pixel drive circuit configured to supply a first signal and a second signal that is different from the first signal to each of the pixel electrodes, the first signal being switched to the second signal or the second signal being switched to the first signal by each of the frames, at a switching timing,
wherein the counter electrodes are applied with a common voltage signal of which a polarity is inverted in a polarity cycle of a polarity cycle period;
wherein the first signal has, in all of the polarity cycle periods, a same phase with the common voltage signal;
wherein the second signal has,
in a first-second voltage period of the polarity cycle period, one of a first voltage and a second voltage, each of which is a voltage of a reverse phase to the common voltage signal, and
in a third voltage period of the polarity cycle period, a third voltage that is between the first voltage and the second voltage,
the first-second voltage period and the third voltage period are alternately repeated; and
wherein the switching timing is when the second signal is switched from the first voltage or the second voltage to the third voltage.
2. The liquid crystal display device according to claim 1 ,
wherein the pixel drive circuit controls the timing of switching the second signal from the first voltage or the second voltage to the third voltage so as to correspond to lines to which display driving is performed by the display drive unit.
3. The liquid crystal display device according to claim 2 ,
wherein the pixel drive circuit switches the second signal from the first voltage or the second voltage to the third voltage in accordance with the timing of rewriting memory contents of the pixels.
4. The liquid crystal display device according to claim 1 ,
wherein the pixel drive circuit controls the second signal in accordance with an ambient temperature.
5. The liquid crystal display device according to claim 4 , wherein the pixel drive circuit controls, when the ambient temperature is higher than a predetermined temperature, the third voltage to have a voltage of one of the first voltage and the second voltage that has the reverse phase to the common voltage signal.
6. The liquid crystal display device according to claim 5 ,
wherein the pixel drive circuit adjusts a value of the third voltage in accordance with the ambient temperature.
7. The liquid crystal display device according to claim 5 ,
wherein the pixel drive circuit adjusts a period of supplying the third voltage in accordance with the ambient temperature.
8. A drive method to be used when driving a liquid crystal display device in which pixels having a memory function are arranged and which includes:
pixel electrodes constituting the pixels arranged in a matrix; and
counter electrodes disposed opposed to the pixel electrodes, liquid crystal capacitors of the pixel being formed between the pixel electrodes and the counter electrodes,
the drive method comprising:
performing display driving by a driving method for obtaining halftone gray scales by setting frames as one cycle and temporarily changing gray scales of respective pixels within one cycle, by a display drive unit;
supplying a first signal and a second signal that is different from the first signal, by a pixel drive circuit to each of the pixel electrodes, the first signal being switched to the second signal or the second signal being switched to the first signal by each of the frames, at a switching timing; and
applying a common voltage signal of which a polarity is inverted in a polarity cycle of a polarity cycle period, to the counter electrodes,
wherein the first signal has, in all of the polarity cycle periods, a same phase with the common voltage signal; and
wherein the second signal has,
in a first-second voltage period of the polarity cycle period, one of a first voltage and a second voltage, each of which is a voltage of a reverse phase to the common voltage signal, and
in a third voltage period of the polarity cycle period a third voltage between the first voltage and the second voltage,
the first-second voltage period and the third voltage period are alternately repeated; and
wherein the switching timing is when the second signal is switched from the first voltage or the second voltage to the third voltage.
9. An electronic apparatus including a liquid crystal display device in which pixels having a memory function are arranged and which comprises:
pixel electrodes constituting the pixels arranged in a matrix;
counter electrodes disposed opposed to the pixel electrodes, liquid crystal capacitors of the pixel being formed between the pixel electrodes and the counter electrodes;
a display drive unit configured to perform display driving by a driving method for obtaining halftone gray scales by setting frames as one cycle and temporarily changing gray scales of respective pixels within one cycle; and
a pixel drive circuit configured to supply a first signal and a second signal that is different from the first signal to each of the pixel electrodes, the first signal being switched to the second signal or the second signal being switched to the first signal by each of the frames, at a switching timing,
wherein the counter electrodes are applied with a common voltage signal of which a polarity is inverted in a polarity cycle of a polarity cycle period;
wherein the first signal has, in all of the polarity cycle periods, a same phase with the common voltage signal;
wherein the second signal has,
in a first-second voltage period of the polarity cycle period, one of a first voltage and a second voltage, each of which is a voltage of a reverse phase to the common voltage signal, and
in a third voltage period of the polarity cycle period, a third voltage that is between the first voltage and the second voltage,
the first-second voltage period and the third voltage period are alternately repeated; and
wherein the switching timing is when the second signal is switched from the first voltage or the second voltage to the third voltage.