Liquid crystal display element, driving method of the same, and electronic paper having the same

1. A method of driving a liquid crystal display element comprising:

a first step for initializing a liquid crystal in a pixel and displaying an initial grayscale at the pixel; and

a second step for displaying a desired grayscale lower than the initial grayscale by making a cumulative time difference between low grayscales lower than a reference grayscale longer than a cumulative time difference between high grayscales higher than the reference grayscale, where the cumulative time differences are a difference between a cumulative voltage application time of voltage pulses cumulatively applied to display a grayscale lower than the initial grayscale and a cumulative voltage application time of the voltage pulses cumulatively applied to display a grayscale one level lower than the grayscale lower than the initial grayscale.

2. The method of driving a liquid crystal display element according to claim 1 , wherein the second step includes a plurality of sub-steps for applying the voltage pulses having equal voltage values and different pulse widths to the liquid crystal.

3. The method of driving a liquid crystal display element according to claim 2 , wherein the second step includes a plurality of sub-step groups for executing part of the plurality of sub-steps in one frame.

4. The method of driving a liquid crystal display element according to claim 3 , wherein the second step is terminated when the execution of part of the plurality of sub-step groups is finished.

5. The method of driving a liquid crystal display element according to claim 3 , wherein a reference voltage is applied to initialize the liquid crystal at the first step.

6. The method of driving a liquid crystal display element according to claim 1 , wherein a relatively high grayscale included in the high grayscales is displayed at the pixel prior to a relatively low grayscale included in the low grayscales at the second step.

7. The method of driving a liquid crystal display element according to claim 1 , wherein a grayscale which is one level lower than an m/2 n -th grayscale is set as the reference grayscale where n represents a number of the reference grayscales to be set and m represents a number of grayscales to be displayed at the pixel and wherein the cumulative time differences on both sides of the reference grayscale serving as a boundary are different from each other.

8. The method of driving a liquid crystal display element according to claim 7 , wherein a cumulative number of applications of the voltage pulses within a range in which the cumulative time differences are equal to each other is given by log 2 t where t represents a number of the grayscales included in the range (t is a power of 2).

9. The method of driving a liquid crystal display element according to claim 1 , wherein the initial grayscale is a highest grayscale.

10. A liquid crystal display element comprising:

a liquid crystal enclosed between a pair of substrates;

a pixel including the liquid crystal and a pair of electrodes sandwiching the liquid crystal; and

a driving device for displaying a multiplicity of grayscales by performing a first step for initializing the liquid crystal in the pixel and displaying an initial grayscale at the pixel and a second step for displaying a desired grayscale lower than the initial grayscale by making a cumulative time difference between low grayscales lower than a reference grayscale longer than a cumulative time difference between high grayscales higher than the reference grayscale, where the cumulative time differences are a difference between a cumulative voltage application time of voltage pulses cumulatively applied to display a grayscale lower than the initial grayscale and a cumulative voltage application time of the voltage pulses cumulatively applied to display a grayscale one level lower than the grayscale lower than the initial grayscale.

11. The liquid crystal display element according to claim 10 , wherein the second step includes a plurality of sub-steps for applying voltage pulses having equal voltage values and different pulse widths to the liquid crystal.

12. The liquid crystal display element according to claim 11 , wherein the second step includes a plurality of sub-step groups for executing part of the plurality of sub-steps in one frame.

13. The liquid crystal display element according to claim 12 , wherein the driving device terminates the second step when the execution of part of the plurality of sub-step groups is finished.

14. The liquid crystal display element according to claim 10 , wherein the driving device displays a relatively high grayscale included in the high grayscales at the pixel prior to a relatively low grayscale included in the low grayscales at the second step.

15. The liquid crystal display element according to claim 10 , wherein the driving device sets a grayscale which is one level lower than an m/2 n -th grayscale as the reference grayscale where n represents a number of the reference grayscales to be set and m represents a number of grayscales to be displayed at the pixel to make the reference grayscale serves as a boundary between the cumulative time differences different from each other.

16. The liquid crystal display element according to claim 15 , wherein the cumulative number of applications of voltage pulses within a range in which cumulative time differences are equal to each other is given by log 2 t where t represents the number of grayscales included in the range (t is a power of 2).

17. The liquid crystal display element according to claim 10 , wherein the initial grayscale is a highest grayscale.

18. The liquid crystal display element according to claim 10 , wherein the driving device shorts the pair of electrodes to a reference potential to initialize the liquid crystal at the first step.

19. An electronic paper comprising a liquid crystal display element according to claim 10 .

20. The electronic paper according to claim 19 , comprising at least two write modes resulting in different states of display.