Method for driving a liquid crystal display device

1. A method for driving a liquid crystal display device including pixel electrodes, counter electrodes and liquid crystal provided between the pixel electrode and the counter electrodes, to suppress an uneven distribution of ions in the liquid crystal, the method comprising the steps of:

applying a common voltage to the counter electrodes;

applying a first image signal to the pixel electrodes;

applying a second image signal to the pixel electrodes,

applying a first clock for starting a frame period;

applying a second clock for changing a polarity of the first and second image signals,

applying another second clock for again changing a polarity of the first and second image signals, and

applying another first clock after said another second clock has been applied, wherein:

the first image signal has a positive polarity with reference to the common voltage,

the second image signal has a negative polarity with reference to the common voltage,

the first image signal and the second image signal are applied to respective pixels at the same position,

the common voltage drifts from an intermediate value of the first image signal and the second image signal,

the first image signal is applied to the liquid crystal during a first applying period started by the second clock,

the second image signal is applied to the liquid crystal during a second applying period started by the another second clock,

the frame period is repeated periodically,

a time spacing between said second clock and said another second clock is shorter than a time spacing between said first clock and said another first clock,

the second applying period is longer than the first applying period to thereby suppress the uneven distribution of ions in the liquid crystal, and

the another first clock and the another second clock are output asynchronously.

2. A method for driving a liquid crystal display device according to claim 1 , wherein the liquid crystal display device is a reflective-type liquid crystal display device for a projector.

3. A method for driving a liquid crystal display device according to claim 1 , wherein the method further includes a step of detecting a quantity of light emitted from a pixel of the liquid crystal display device and setting a length of the first period in response to the quantity of light.

4. A method for driving a liquid crystal display device according to claim 1 , wherein the method further includes a step of detecting a quantity of light emitted from a pixel for detection and setting a length of the first period in response to the quantity of light.

5. A method for driving a liquid crystal display device according to claim 1 , wherein the method further includes a step of setting the first period based on a radiation time accumulated quantity of light radiated to the liquid crystal display device.

6. A method for driving a liquid crystal display device including a display region on which a plurality of pixels are formed, pixel electrodes which are provided to the pixels, counter electrodes which face the pixel electrodes in an opposed manner, a liquid crystal provided between the pixel electrode and the counter electrodes and an image memory which stores display data, to suppress an uneven distribution of ions in the liquid crystal, the method comprising the steps of:

applying a common voltage to the counter electrodes;

storing display data in the image memory;

starting a first polarity period in response to outputting of a first polarity changeover signal;

starting a second polarity period in response to outputting of a second polarity changeover signal;

applying a first clock for starting a frame period,

applying another first clock after said second polarity changeover signal has been applied;

applying video signals of first polarity to the liquid crystal during the first polarity applying period started by the first polarity changeover signal; and

applying video signals of second polarity to the liquid crystal during the second polarity applying period started by the second polarity changeover signal, wherein:

the video signals of the first polarity and the second polarity are applied to respective pixels at the same position,

a second polarity and a first polarity have reverse polarities from each other with reference to a common voltage,

the common voltage drifts from an intermediate value of the signal of first polarity and the signal of second polarity,

a first video signal and a second video signal are voltages in conformity with display data stored in the image memory,

the frame period is repeated periodically,

a time spacing between the first polarity changeover signal and the second polarity changeover signal is shorter than a time spacing between the first clock and said another first clock,

the first polarity applying period and the second polarity applying period differ in length to thereby suppress the uneven distribution of ions in the liquid crystal, and

the another first clock and the second polarity changeover signal are output asynchronously.

7. A method for driving a liquid crystal display device according to claim 6 , wherein the liquid crystal display device is a reflective-type liquid crystal display device for a projector.

8. A method for driving a liquid crystal display device according to claim 6 , wherein the method further includes a step of detecting a quantity of light emitted from a pixel of the liquid crystal display device and setting a length of the first period in response to the quantity of light.

9. A method for driving a liquid crystal display device according to claim 6 , wherein the method further includes a step of detecting a quantity of light emitted from a pixel for detection and setting a length of the first period in response to the quantity of light.

10. A method for driving a liquid crystal display device according to claim 6 , wherein the method further includes a step of setting the first period based on a radiation time accumulated quantity of light radiated to the liquid crystal display device.

11. A method for driving a liquid crystal display device, including a display region on which a plurality of pixels are formed, pixel electrodes which are provided to the pixels, counter electrodes which face the pixel electrodes in an opposed manner, a liquid crystal provided between the pixel electrode and the counter electrodes and an image memory which stores display data, to suppress an uneven distribution of ions in the liquid crystal, the method comprising the steps of:

applying a common voltage to the counter electrodes;

storing display data for one display region in the image memory;

outputting a first polarity changeover signal in an interval between a first display start signal and a second display start signal and, thereafter, outputting a second polarity changeover signal;

starting a first polarity period in response to outputting of the first polarity changeover signal;

starting a second polarity period in response to outputting of the second polarity changeover signal;

applying a first clock for starting a frame period,

applying another first clock after said second polarity changeover signal has been applied;

applying video signals of first polarity to the liquid crystal during the first polarity applying period started by the first polarity changeover signal; and

applying video signals of second polarity to the liquid crystal during the second polarity applying period started by the second polarity changeover signal, wherein:

the video signals of the first polarity and the second polarity are applied to respective pixels at the same position,

a second polarity and a first polarity have reverse polarities from each other with reference to a common voltage,

the common voltage drifts from an intermediate value of the signal of first polarity and the signal of second polarity,

a first video signal and a second video signal are voltages in conformity with display data stored in the image memory,

the frame period is repeated periodically,

a time spacing between the first polarity changeover signal and the second polarity changeover signal is shorter than a time spacing between the first clock and said another first clock, and

the first polarity applying period and the second polarity applying period differ in length to thereby suppress the uneven distribution of ions in the liquid crystal, and

the first clock and the second polarity changeover signal are output asynchronously.

12. A method for driving a liquid crystal display device according to claim 11 , wherein the liquid crystal display device is a reflective-type liquid crystal display device for a projector.

13. A method for driving a liquid crystal display device according to claim 11 , wherein the method further includes a step of detecting a quantity of light emitted from a pixel of the liquid crystal display device and setting a length of the first period in response to the quantity of light.

14. A method for driving a liquid crystal display device according to claim 11 , wherein the method further includes a step of detecting a quantity of light emitted from a pixel for detection and setting a length of the first period in response to the quantity of light.

15. A method for driving a liquid crystal display device according to claim 11 , wherein the method further includes a step of setting the first period based on a radiation time accumulated quantity of light radiated to the liquid crystal display device.

16. A method for driving a liquid crystal display device according to claim 6 , wherein the video signals of the first polarity are applied to the pixel electrodes during the first polarity period and the video signals of the second polarity are applied to the pixel electrodes during the second polarity period.

17. A method for driving a liquid crystal display device according to claim 11 , wherein the video signals of the first polarity are applied to the pixel electrodes during the first polarity period and the video signals of the second polarity are applied to the pixel electrodes during the second polarity period.