Liquid crystal display panel, stack type liquid crystal display panel and driving method

A stack type liquid crystal display panel, comprising:

• a first liquid crystal display panel comprising:
• pixel electrodes which are arranged in a two-dimensional matrix;
• an active matrix substrate which includes switching elements arranged in a matrix in a one-to-one relationship with the pixel electrodes to control application and interruption of a voltage to the pixel electrodes;
• an opposing substrate which includes a common electrode opposing the pixel electrodes;
• and
• a liquid crystal layer disposed between the pixel electrodes and the common electrode, the liquid crystal layer showing cholesteric phase at a temperature of 25° C., wherein different voltages are applied to the liquid crystal layer in each of 1) an image erasing period, 2) an image writing period and 3) an image displaying period, and thereby a state of the liquid crystal layer is changed in an order of erasing an image, writing an image and displaying an image, wherein a first time period Tw of applying a writing voltage to the liquid crystal layer during the image writing period is set longer than or equal to a second time period for applying the writing voltage to the liquid crystal layer in which a variation ΔVs is less than or equal to a predetermined value, wherein ΔVs for the second time period is defined to be an absolute value of a difference of 1) a first writing voltage for obtaining approximately 50% of a maximum reflectance for the liquid crystal layer at a first predetermined temperature and 2) a second writing voltage for obtaining approximately 50% of a maximum reflectance for the liquid crystal layer at a second predetermined temperature;
• and
• a second liquid crystal display panel stacked on said first liquid crystal panel, wherein said second liquid crystal display has a structure substantially identical to said first liquid crystal panel;
• and
• wherein the time period Tw of applying the writing voltage to the liquid crystal layers of the stacked liquid crystal display panels is the same for all of the stacked liquid crystal display panels.

A liquid crystal display panel, comprising:

• pixel electrodes which are arranged in a two-dimensional matrix;
• an active matrix substrate which includes switching elements arranged in a matrix in a one-to-one relationship with the pixel electrodes to control application and interruption of a voltage to the pixel electrodes;
• an opposing substrate which includes a common electrode opposing the pixel electrodes;
• and
• a liquid crystal layer disposed between the pixel electrodes and the common electrode, the liquid crystal layer showing cholesteric phase at a temperature of 25° C., wherein different voltages are applied to the liquid crystal layer in each of 1) an image erasing period for resetting the liquid crystal layer included in an area for writing into a predetermined state so as to erase an image, 2) an image writing period for writing an image and 3) an image displaying period for displaying an image, wherein a first time period Tw of applying a writing voltage, wherein the writing voltage has a value that ranges from a maximum voltage Vh for writing a desired maximum reflectance for the liquid crystal layer at a predetermined temperature to a minimum voltage Vl for writing a desired minimum reflectance for the liquid crystal layer at the predetermined temperature, to the liquid crystal layer during the image writing period and wherein the first time period is set longer than or equal to a second time period for applying the writing voltage to the liquid crystal layer in which ΔVs for the second time period is equal to a predetermined value and wherein ΔVs is defined to be an absolute value of a difference of 1) a first writing voltage for obtaining approximately 50% of a maximum reflectance for the liquid crystal layer at 50° C. and 2) a second writing voltage for obtaining approximately 50% of a maximum reflectance for the liquid crystal layer at 0° C., wherein the predetermined value is 10% of an absolute value of a difference between the maximum writing voltage Vh and the minimum writing voltage Vl.

A stack type liquid crystal display panel, comprising:

• a first liquid crystal display panel, comprising:
• pixel electrodes which are arranged in a two-dimensional matrix;
• an active matrix substrate which includes switching elements arranged in a matrix in a one-to-one relationship with the pixel electrodes to control application and interruption of a voltage to the pixel electrodes;
• an opposing substrate which includes a common electrode opposing the pixel electrodes;
• and
• a liquid crystal layer disposed between the pixel electrodes and the common electrode, the liquid crystal layer showing cholesteric phase at a temperature of 25° C., wherein different voltages are applied to the liquid crystal layer in each of an image erasing period for resetting the liquid crystal layer included in an area for writing into a predetermined state so as to erase an image, an image writing period for writing an image and an image displaying period for displaying an image, wherein a first time period Tw of applying a writing voltage to the liquid crystal layer during the image writing period is set longer than or equal to a second time period in which a difference between the writing voltage at 0° C. and the writing voltage at 50° C., both voltages for making the liquid crystal layer display an image of approximate 50% of a maximum reflectance and in which a 10% of a difference between a maximum and minimum writing voltages at a temperature of 25° C. exists;
• a second liquid crystal display panel stacked on said first liquid crystal panel, wherein the second liquid crystal display has a structure substantially identical to the first liquid crystal panel;
• and
• wherein the first time period Tw of applying the writing voltage to the liquid crystal layers of the stacked liquid crystal display panels is the same for all of the stacked liquid crystal display panels.

A driving method for a liquid crystal display panel comprising:

• pixel electrodes arranged in a two-dimensional matrix, an active matrix substrate including switching elements arranged in a matrix in a one-to-one relationship with the pixel electrodes to control-application and interruption of a voltage to the pixel electrodes, an opposing substrate including a common electrode opposing the pixel electrodes, and a liquid crystal layer disposed between the pixel electrodes and the common electrode, the liquid crystal layer showing cholesteric phase at a temperature of 25° C., the driving method comprising:
• applying an erase voltage to the liquid crystal layer to erase an image;
• applying a writing voltage to the liquid crystal layer to write an image, wherein the writing voltage has a value that ranges from a maximum voltage Vh for writing a desired maximum reflectance for the liquid crystal layer at a predetermined temperature to a minimum voltage Vl for writing a desired minimum reflectance for the liquid crystal layer at the predetermined temperature;
• applying a display voltage to the liquid crystal layer to display an image;
• wherein a first time period Tw of applying the writing voltage to the liquid crystal layer is set to be longer than or equal to a second time period for applying the writing voltage to the liquid crystal layer in which a variation ΔVs for the second time period is a predetermined value, wherein ΔVs is defined to be an absolute value of a difference of 1) a first writing voltage for obtaining approximately 50% of a maximum reflectance for the liquid crystal layer at 40° C. and 2) a second writing voltage for obtaining approximately 50% of a maximum reflectance for the liquid crystal layer at 10° C., wherein the predetermined value is 10% of an absolute difference between Vh and Vl.