Electrophoretic display and driving method thereof

An electrophoretic display (EPD) and a driving method thereof. The electrophoretic display (EPD) includes: an upper substrate and a lower substrate arranged opposite to each other, and an electrophoretic medium disposed between the upper substrate and the lower substrate; the EPD is provided with a plurality of pixels; each pixel includes at least two sub-pixels; colored charged particles of different colors are disposed in different sub-pixels of each pixel; and a first wall electrode and a second wall electrode are respectively disposed on two opposite sides of each sub-pixel.

TECHNICAL FIELD

The present disclosure relates to an electrophoretic display (EPD) and a driving method thereof.

BACKGROUND

An EPD is a display device which achieves display by controlling the distribution of charged particles via electrical field and changing the reflection effect of the charged particles upon ambient light. Because the EPD can achieve display by directly utilizing the ambient light and does not require a backlight module, the power consumption is low, so that the EPD receives more and more extensive attention.

SUMMARY

Embodiments of the present disclosure provide an EPD and a driving method thereof, which are used for achieving color display.

The electrophoretic display (EPD) comprises: an upper substrate and a lower substrate arranged opposite to each other, and an electrophoretic medium disposed between the upper substrate and the lower substrate; the EPD is provided with a plurality of pixels; each pixel includes at least two sub-pixels; colored charged particles of different colors are disposed in different sub-pixels of each pixel; and a first wall electrode and a second wall electrode are respectively disposed on two opposite sides of each sub-pixel.

In addition, an embodiment of the present disclosure provides a method for driving the above-mentioned electrophoretic display (EPD).

The driving method comprises: controlling an electrical field generated between the first wall electrode and the second wall electrode of each sub-pixel, so that the colored charged particles in the sub-pixel can be migrated towards the first wall electrode or the second wall electrode, and hence an amount of light reflected by the colored charged particles in a corresponding sub-pixel can be controlled.

REFERENCE NUMERALS OF THE ACCOMPANYING DRAWINGS

1—upper substrate11—shielding structure;42′—black charged particle in the prior art;2—lower substrate;22—light absorbing layer;3′—electrophoretic medium in the prior art;3—electrophoretic medium41—red charged particle;11′—first electrode in the prior art;4—colored charged particle;5—first wall electrode;4′—charged particle in the prior art;7—retaining wall;8—black charged particle;1′—upper substrate in the prior art;43—blue charged particle;6—second wall electrode21′—second electrode in the prior art;21—base substrate;42—green charged particle;41′—black charged particle in the prior art;2′—lower substrate in the prior art.

DETAILED DESCRIPTION

FIG. 1illustrates an EPD, which comprises an upper substrate1′ and a lower substrate2′ arranged opposite to each other, and an electrophoretic medium3′ disposed between the upper substrate1′ and the lower substrate2′. First electrodes11′ are disposed on the upper substrate1′; second electrodes21′ are disposed on the lower substrate2; the EPD is divided into a plurality of pixels; each pixel is provided with charged particles4; the charged particles4′ include a plurality of white charged particles41′ and a plurality of black charged particles42; and charges of the white charged particles41′ and charges of the black charged particles42′ are of different types, so that the direction of the electrical fields between the first electrodes11′ and the second electrodes21′ of the pixel can be changed, namely whether the pixel displays white or black can be changed. The EPD as illustrated inFIG. 1can only achieve black display and white display and cannot achieve color display, and hence is unfavorable for the wide application of the EPD.

Embodiments of the present disclosure provide an EPD and a driving method thereof, which are used for achieving color display.

The EPD comprises an upper substrate and a lower substrate arranged opposite to each other, and an electrophoretic medium disposed between the upper substrate and the lower substrate. The EPD is provided with a plurality of pixels, each pixel includes at least two sub-pixels; colored charged particles of different colors are disposed in different sub-pixels of each pixel; and a first wall electrode and a second wall electrode are respectively disposed on two opposite sides of each sub-pixel.

An embodiment of the present disclosure provides the foregoing EPD. Each pixel in the EPD includes at least two sub-pixels, the colored charged particles of different colors are disposed in different sub-pixels of each pixel, and the first wall electrode and the second wall electrode are respectively disposed on the two opposite sides of each sub-pixel so as to isolate the sub-pixels, thus, by controlling the direction and magnitude of the electrical field generated between the first wall electrode and the second wall electrode of each sub-pixel, the migration of the colored charged particles in the sub-pixel towards the first wall electrode or the second wall electrode can be controlled, the amount of migration of the colored charged particles can be controlled, the amount of light reflected by the colored charged particles in each sub-pixel can be controlled, and the color displayed by each pixel can be controlled, and hence the EPD can achieve color display.

In addition, an embodiment of the present disclosure further provides a method for driving an EPD. The driving method is used for driving the foregoing EPD.

The driving method comprises: controlling the electrical field generated between the first wall electrode and the second wall electrode of each sub-pixel, so that the colored charged particles in the sub-pixel can be migrated towards the first wall electrode or the second wall electrode, and hence the amount of light reflected by the colored charged particles in corresponding sub-pixel can be controlled.

An embodiment of the present disclosure provides a driving method of the foregoing EPD. In the driving method, by controlling the direction and magnitude of the electrical field generated between the first wall electrode and the second wall electrode of each sub-pixel, the migration of the colored charged particles in the sub-pixel towards the first wall electrode or the second wall electrode can be controlled; the amount of migration of the colored charged particles can be controlled; the amount of light reflected by the colored charged particles in each sub-pixel can be controlled; the color displayed by each pixel can be controlled; and hence the EPD can achieve color display.

First Embodiment

The first embodiment provides an EPD. As illustrated inFIGS. 2 and 3, the EPD comprises an upper substrate1and a lower substrate2arranged opposite to each other, and an electrophoretic medium3disposed between the upper substrate1and the lower substrate2. Specifically, the EPD is divided into a plurality of pixels; each pixel includes at least two sub-pixels; colored charged particles of different colors are disposed in different sub-pixels of each pixel; and a first wall electrode5and a second wall electrode6are respectively disposed on two opposite sides of each sub-pixel so as to isolate the sub-pixels.

In addition, for instance, as illustrated inFIG. 3, in the first embodiment of the present disclosure, both ends of each first wall electrode5respectively make contact with the upper substrate1and the lower substrate2, and both ends of each second wall electrode6also respectively make contact with the upper substrate1and the lower substrate2, so that the electrical field between the first wall electrode5and the second wall electrode6can have good controllability on the colored charged particles4.

The embodiment of the present disclosure provides the foregoing EPD. Each pixel in the EPD includes at least two sub-pixels; the colored charged particles4of different colors are disposed in different sub-pixels of each pixel; and the first wall electrode5and the second wall electrode6are respectively disposed on the two opposite sides of each sub-pixel so as to isolate the sub-pixels. Thus, by controlling the direction and magnitude of the electrical field generated between the first wall electrode5and the second wall electrode6of each sub-pixel, the migration of the colored charged particles4in the sub-pixel towards the first wall electrode5or the second wall electrode6can be controlled; the amount of migration of the colored charged particles4can be controlled; the amount of light reflected by the colored charged particles4in each sub-pixel can be controlled; the color displayed by each pixel can be controlled; and hence the EPD can achieve color display.

It should be noted that the expression that “the first wall electrode5and the second wall electrode6are respectively disposed on the two opposite sides of each sub-pixel so as to isolate the sub-pixels” does not define whether there are other structures between two adjacent sub-pixels so as to isolate the sub-pixels, and also does not define structures disposed on the other two opposite sides of each sub-pixel. The specific implementation for isolating the sub-pixels may be of various kinds. Illustratively, the embodiment of the present disclosure provides the following two specific implementations.

First specific implementation: when both ends of each first wall electrode5respectively make contact with the upper substrate1and the lower substrate2and both ends of each second wall electrode6also respectively make contact with the upper substrate1and the lower substrate2, as illustrated inFIG. 3(a sectional view ofFIG. 2along direction AA′), only the first wall electrode5or the second wall electrode6is disposed between two adjacent sub-pixels, namely the sub-pixels may be isolated from each other in the direction. At this point, as illustrated inFIG. 3, the first wall electrodes5and the second wall electrodes6are alternately arranged. As illustrated inFIG. 4(a sectional view ofFIG. 2along direction BB′), a retaining wall7is respectively disposed on the other two opposite sides of each sub-pixel so as to isolate the sub-pixels in the direction. At this point, two adjacent sub-pixels share one first wall electrode5or one second wall electrode6. Thus, the quantity of structure components between the sub-pixels is small; the thickness of the structures between the sub-pixels is small; the structure and the driving method of the EPD is simplified; the cost of the EPD is low; and the aperture ratio of the EPD is increased.

Second specific implementation: four retaining walls7are disposed on the periphery of each sub-pixel; a closed rectangular frame is encircled by the four retaining walls7. As illustrated inFIG. 5, the first wall electrode5or the second wall electrode6is respectively disposed on both sides of the retaining wall7between two adjacent sub-pixels; the retaining wall7and the wall electrodes (the collective name of the first wall electrode5and the second wall electrode6) on both sides thereof are configured to together isolate the sub-pixels in the direction; the retaining walls7are respectively disposed on the other two opposite sides of each sub-pixel so as to isolate the sub-pixels in that direction; and the sectional view in the direction may refer toFIG. 4in the first specific implementation.

In addition, in the embodiment of the present disclosure, the first wall electrodes5may be formed on the upper substrate1and the second wall electrodes6may be formed on the lower substrate2; or one part of the first wall electrodes5and one part of the second wall electrodes6are formed on the upper substrate and the other part of the first wall electrodes5and the other part of the second wall electrodes6are formed on the lower substrate2; or both the first wall electrodes5and the second wall electrodes6are formed on the same substrate, e.g., the upper substrate1or the lower substrate2. When both the first wall electrodes5and the second wall electrodes6are formed on the same substrate (the upper substrate1or the lower substrate2), the manufacturing method of the first wall electrodes5and the second wall electrodes6is simple, so that the manufacturing method of the EPD can be simplified. In the manufacturing process of the first wall electrodes5and the second wall electrodes6, an electrode layer may be formed by sputtering on the upper substrate1or the lower substrate2at first, and subsequently, the electrode layer is patterned to form the pattern including the first wall electrodes5and the second wall electrodes6. Illustratively, the material of the first wall electrodes5and the second wall electrodes6may be a metal or transparent conductive material (e.g., indium tin oxide (ITO)).

Optionally, as illustrated inFIG. 3, the EPD provided by the embodiment of the present disclosure further comprises a shielding structure11disposed on the upper substrate1. The position of the shielding structure corresponds to the position of the first wall electrode5and/or the second wall electrode6. The shielding structure11is configured to shield the colored charged particles4migrated to the first wall electrode5or the second wall electrode6, so as to prevent light reflected by this part of colored charged particles4from entering the human eyes, and hence the display effect of the EPD can be guaranteed. The expression that “the position of the shielding structure11corresponds to the position of the first wall electrode5and/or the second wall electrode6” refers to that a projection of the shielding structure11on the lower substrate and a projection of the first wall electrode5and/or the second wall electrode6on the lower substrate have an overlap section therebetween. If the charges of all the colored charged particles are of the same type, the shielding structures11may be only disposed at positions corresponding to the first wall electrodes5or the second wall electrodes6, so that the structure of the EPD can be simplified. At this point, the driving method of the EPD needs to match with the structure. For instance, the shielding structures11are only disposed at positions of the upper substrate1corresponding to the first wall electrodes5. When all the colored charged particles4are positively charged, in the display process of the EPD, a low voltage can be applied to the first wall electrodes5and a high voltage can be applied to the second wall electrodes6, so that the colored charged particles4are migrated towards the first wall electrodes5, and hence the colored charged particles4migrated to the first wall electrodes5are shielded. When the charges of the colored charged particles4in all the sub-pixels are of different types, or when the shielding structures11are only disposed at positions of the upper substrate1corresponding to the second wall electrodes6, the driving method of the EPD may be correspondingly selected by those skilled in the art according to the above content. No further redundant description will be given here.

The shielding structure11may be a black film or a white film; because the white film can reflect light, the display effect of the EPD can be affected to a certain degree. Thus, for instance, in an embodiment of the present disclosure, the shielding structure11may be a black film. Moreover, for instance, the shielding structure11is a black resin layer with a low cost and a simple manufacturing process.

Detailed description will be given below to the upper substrate1, the lower substrate2, the electrophoretic medium3and the colored charged particles4in the EPD provided by an embodiment of the present disclosure.

Optionally, the upper substrate1provided by the embodiment of the present disclosure may be a transparent glass substrate or a quartz substrate. The lower substrate2may be a transparent substrate or a quartz substrate. At this point, light irradiated to the lower substrate can run through the lower substrate2. As illustrated inFIG. 3, the lower substrate2may also include a base substrate21and a light absorbing layer22disposed on the base substrate21. At this point, the lower substrate2may absorb light irradiated to the lower substrate. The base substrate21may be a transparent glass substrate or a quartz substrate. The light absorbing layer22may be a black resin layer with a low cost and a simple manufacturing method.

Optionally, the material of the electrophoretic medium3in the embodiment of the present disclosure may be cellulose acetate, agarose gel, polyacrylamide gel, etc.

Optionally, each pixel in the embodiment of the present disclosure includes a red sub-pixel, a green sub-pixel and a blue sub-pixel; the red sub-pixel is provided with red charged particles41; the green sub-pixel is provided with green charged particles42; and the blue sub-pixel is provided with blue charged particles43. The red charged particles41, the green charged particles42and the blue charged particles43may be all charged pigmented polymer particles. The diameter of the pigmented polymer particles may be from 50 nm-1,000 nm, for instance, be from 150 nm-600 nm.

In addition, in the embodiment of the present disclosure, the charges of all the colored charged particles4may be of the same type. Or when all the colored charged particles4in each sub-pixel carry the same type of charges, the colored charged particles4in one part of sub-pixels are positively charged and the colored charged particles4in the other part of sub-pixels are negatively charged. No limitation will be given here in the embodiment of the present disclosure. Optionally, the sub-pixel of the EPD may be only provided with the colored charged particles4or may be provided with black charged particles8as well. Detailed description will be given below to the above two EPDs in the embodiment of the present disclosure.

Optionally, when the sub-pixel is only provided with the colored charged particles4, the density of the colored charged particles4may be less than that of the electrophoretic medium3. Thus, when there is no electrical field generated between the first wall electrode5and the second wall electrode6as illustrated inFIG. 3, the colored charged particles4are disposed on the electrophoretic medium3. Therefore, when light is irradiated to and reflected by the colored charged particles4, the light will not run through the electrophoretic medium4, so that the light utilization can be high. In addition, the quantity of the colored charged particles4must satisfy the following conditions: when there is no electrical field generated between the first wall electrode5and the second wall electrode6, the colored charged particles4at least cover the electrophoretic medium3. Thus, when the EPD displays white, all the light can be reflected by the colored charged particles4and no light is irradiated to the lower substrate1. Thus, the light utilization is high, and hence the EPD can have higher brightness when displaying white.

Detailed description will be given below on how to achieve color display in the EPD with the above structure by taking the following as an example: all the colored charged particles4carry the same type of charges; each pixel includes a red sub-pixel, a green sub-pixel and a blue sub-pixel; the red sub-pixel is provided with red charged particles41; the green sub-pixel is provided with green charged particles42; and the blue sub-pixel being provided with blue charged particles43.

If there is no electrical field generated between all the first wall electrodes5and all the second wall electrodes6(this status may be achieved by not applying voltage or applying same voltage to both), as illustrated inFIGS. 3 and 5, all the colored charged particles4are disposed on the electrophoretic medium3and can reflect light. At this point, the amount of light reflected by the colored charged particles in the sub-pixels of each pixel is same, so that all the pixels can display white, and hence the EPD can display white.

If the electrical fields generated between all the first wall electrodes5and all the second wall electrodes6are greater than or equal to a critical value, as illustrated inFIG. 6, all the colored charged particles4are migrated to the first wall electrodes5or the second wall electrodes6, and the colored charged particles4cannot reflect light, so that light can be irradiated to the lower substrate2. At this point, the display effect of the EPD depends on the lower substrate2. If, as illustrated inFIG. 6, the lower substrate2includes a transparent base substrate21and a light absorbing layer disposed on the base substrate21, the lower substrate2can absorb the light, so that the EPD can display black; and if the lower substrate2is transparent, the EPD is in a transparent state.

If the electrical field between the first wall electrode5and the second wall electrode6of at least one sub-pixel is greater than 0 and less than the critical value, as illustrated inFIG. 7, partial colored charged particles4in the at least one sub-pixel are disposed on the electrophoretic medium3. As for one pixel, if the same amount of colored charged particles4in the three sub-pixels of the pixel are disposed on the electrophoretic medium3, the pixel displays white; and if the amount of the colored charged particles4disposed on the electrophoretic medium3in the three sub-pixels of the pixel is not completely the same, the pixel achieves color display. When all the pixels display white, the EPD displays white; and when at least one pixel achieves color display, the EPD achieves color display. The amount of light reflected by the colored charged particles4in the sub-pixels may be adjusted by adjusting the magnitudes of the electrical fields between the first wall electrodes5and the second wall electrodes6of the sub-pixels within a range of greater than 0 and less than the critical value, so that the pixels can display different colors.

The critical value is the magnitude of the electrical field when all the colored charged particles4are just migrated to the first wall electrode5or the second wall electrode6and may be set according to the electricity quantity of the colored charged particles4, the quantity of the colored charged particles4, the size of the sub-pixel, and other factors. No limitation will be given here. In addition, description is given above to the means of achieving color display in the EPD by only taking the EPD with specific structure as an example. The means of achieving color display when the EPD has other specific structures can be obtained by those skilled in the art on the basis of the above content. No further description will be given here.

Optionally, as illustrated inFIG. 8, when each sub-pixel is not only provided with the colored charged particles4but also provided with the black charged particles8, charges of the black charged particles8and charges of the colored charged particles4are of different types; the density of the colored charged particles4is greater than that of the electrophoretic medium3; and the density of the black charged particles8is less than that of the electrophoretic medium3. For instance, in the embodiment of the present disclosure, in the same electrical field, the migration rate of the black charged particles8is greater than that of the colored charged particles4, so that all the black charged particles5can be disposed on the first wall electrode5or the second wall electrode6when the electrical field between the first wall electrode5and the second wall electrode6reaches a certain value. At this point, the colored charged particles4disposed beneath the electrophoretic medium3will not be shielded by the black charged particles5and can all be configured to reflect light, so that the light utilization can be high. Optionally, as known from the acceleration formula a=qE/m of the charged particles in the electrical field, the migration rate of the black charged particles8can be greater than that of the colored charged particles4in the same electrical field by adoption of the means that the mass of the black charged particles8is less than that of the colored charged particles (if the black charged particles8and the colored charged particles4are made from a same material, the diameter of the black charged particles8is less than that of the colored charged particles4) and/or the means that the electricity quantity of the black charged particles8is greater than that of the colored charged particles4.

In addition, the quantity of the colored charged particles4satisfies the following condition: when there is no electrical field between the first wall electrode5and the second wall electrode6, the colored charged particles4cover a lower surface of the electrophoretic medium3, so that the brightness can be higher when the EPD achieves color display or displays white; and the quantity of the black charged particles8also satisfies the following condition: when there is no electrical field between the first wall electrode5and the second wall electrode6, the black charged particles8cover the lower surface of the electrophoretic medium3, so that light of other colors cannot be blended in when the EPD displays black.

Detailed description will be given below on how to achieve color display in the EPD with the above structure by taking the following as an example: all the colored charged particles4carry the same type of charges; all the black charged particles8carry another type of charges; each pixel includes a red sub-pixel, a green sub-pixel and a blue sub-pixel; the red sub-pixel is provided with red charged particles41; the green sub-pixel is provided with green charged particles42; and the blue sub-pixel is provided with blue charged particles43.

If there is no electrical field between all the first wall electrodes5and all the second wall electrodes6, as illustrated inFIG. 8, all the black charged particles8are disposed on the electrophoretic medium3and all the colored charged particles4are disposed beneath the electrophoretic medium3, so that all the colored charged particles4can be shielded by the black charged particles8, and hence the EPD can display black.

If the electrical fields between all the first wall electrodes5and all the second wall electrodes6is greater than the critical value, as illustrated inFIG. 9, all the colored charged particles4and all the black charged particles8are respectively disposed on the first wall electrodes5and the second wall electrodes6, so that the display effect of the EPD depends on the structure of the lower substrate2. If, as illustrated inFIG. 9, the lower substrate2includes a transparent base substrate21and a light absorbing layer disposed on the base substrate21, the lower substrate2can absorb light, and hence the EPD can display black; and if the lower substrate2is transparent, the EPD is in a transparent state.

If the electrical field between the first wall electrode5and the second wall electrode6of at least one sub-pixel is greater than 0 and less than the critical value, as illustrated in HG.10, partial colored charged particles4in the at least one sub-pixel are not shielded by the black charged particles8and can reflect light. As for one pixel, if the same amount of colored charged particles4in the three sub-pixels of the pixel can reflect light, the pixel displays white; and if the amount of the colored charged particles4capable of reflecting light in the three sub-pixels of the pixel is not completely the same, the pixel achieves color display. When all the pixels display white, the EPD displays white; and when at least one pixel achieves color display, the EPD achieves color display. The amount of light reflected by the colored charged particles4in the sub-pixels may be adjusted by adjusting the magnitude of the electrical field between the first wall electrodes5and the second wall electrodes6of the sub-pixels within a range of greater than 0 and less than the critical value, so that the pixels can display different colors.

The critical value is the magnitude of the electrical field when all the colored charged particles4are just migrated to the first wall electrode5or the second wall electrode6and may be set according to the electricity quantity of the colored charged particles4, the quantity of the colored charged particles4, the size of the sub-pixel, and other factors. No limitation will be given here.

Second Embodiment

This embodiment of the present disclosure provides a method for driving an EPD. The driving method is used for driving the EPD provided by the first embodiment. Specifically, as illustrated inFIG. 3, the EPD comprises an upper substrate1and a lower substrate2arranged opposite to each other, and an electrophoretic medium3disposed between the upper substrate1and the lower substrate2. The EPD is divided into a plurality of pixels; each pixel includes at least two sub-pixels; colored charged particles4of different colors are disposed in different sub-pixels of each pixel; and a first wall electrode5and a second wall electrode6are respectively disposed on two opposite sides of each sub-pixel so as to isolate the sub-pixels. The driving method comprises: controlling the electrical field between the first wall electrode5and the second wall electrode6of each sub-pixel, so that the colored charged particles4in the sub-pixel can be migrated towards the first wall electrode5or the second wall electrode6, and hence the amount of light reflected by the colored charged particles4in corresponding sub-pixel can be controlled.

The embodiment of the present disclosure provides a driving method of the foregoing EPD. In the driving method, by controlling the direction and magnitude of the electrical field between the first wall electrode5and the second wall electrode6of each sub-pixel, the migration of the colored charged particles4in the sub-pixel towards the first wall electrode5or the second wall electrode6can be controlled; the amount of migration of the colored charged particles can be controlled; the amount of light reflected by the colored charged particles4in each sub-pixel can be controlled; the color displayed by each pixel can be controlled; and hence the EPD can achieve color display.

The step of controlling the electrical field between the first wall electrode5and the second wall electrode6of each sub-pixel specifically includes: applying the same reference voltage to all the second wall electrodes6, and meanwhile, applying a respective corresponding display voltage to each first wall electrode5. Moreover, the quantity of the colored charged particles4disposed on the electrophoretic medium3in the sub-pixel may be adjusted by adjusting the specific difference between the reference voltage and the display voltage applied to the first wall electrode5of the sub-pixel, and hence the amount of light reflected by the colored charged particles4in the sub-pixel can be adjusted.

It should be noted that: as known from the description in the first embodiment, the specific structure of the EPD may be various, and the specific steps of the driving method corresponding to the EPD may also be different. Illustratively, when the shielding structures11are only disposed on the upper substrate1at positions corresponding to the first wall electrodes5as illustrated inFIG. 3, the magnitude relationship (whether the value is large or small is embodied here, and the specific difference is not embodied) between the display voltage applied to the first wall electrode5of the sub-pixel and the reference voltage applied to the second wall electrode6shall be reasonably set. When there is an electrical field generated between the first wall electrode5and the second wall electrode6of the sub-pixel, the colored charged particles4in the sub-pixel can all be migrated towards the first wall electrode5and hence be shielded by the corresponding shielding structure11. The magnitude relationship is relevant to the type of charges of the colored charged particles4in the sub-pixel. Illustratively, when all the colored charged particles4are positively charged, the display voltage applied to the first wall electrodes5of the sub-pixels may be all less than the reference voltage; and when all the colored charged particles4are negatively charged, the display voltage applied to the first wall electrodes5of the sub-pixels may be all greater than the reference voltage. Thus, when there is an electrical field between the first wall electrode5and the second wall electrode6, the colored charged particles4can be migrated towards the first wall electrode5and hence be shielded by the shielding structure11.

For more clear understanding of the present disclosure by those skilled in the art, detailed description will be given below on how to achieve color display in the EPDs with different structures by taking the following case as an example: all the colored charged particles4carry the same type of charges; each pixel include a red sub-pixel, a green sub-pixel and a blue sub-pixel; the red sub-pixel is provided with red charged particles41; the green sub-pixel is provided with green charged particles42; and the blue sub-pixel is provided with blue charged particles43.

Illustratively, the sub-pixel in the first EPD is only provided with the colored charged particles4, and the density of the colored charged particles4is less than that of the electrophoretic medium3. The means of achieving color display in the EPD is as follows:

If there is no electrical field between all the first wall electrodes5and all the second wall electrodes6(which case may be achieved by not applying voltage or applying same voltage to both), as illustrated inFIGS. 3 and 5, all the colored charged particles4are disposed on the electrophoretic medium3and can all reflect light. At this point, the amount of light reflected by the colored charged particles in the sub-pixels of each pixel is same, so that all the pixels display white, and hence the EPD displays white.

If the electrical fields between all the first wall electrodes5and all the second wall electrodes6is greater than or equal to a critical value, as illustrated inFIG. 6, all the colored charged particles4are migrated to the first wall electrodes5or the second wall electrodes6, and the colored charged particles4cannot reflect light, so that the light can be irradiated to the lower substrate2. At this point, the display effect of the EPD depends on the lower substrate2. If, as illustrated inFIG. 6, the lower substrate2includes a transparent base substrate21and a light absorbing layer disposed on the base substrate21, the lower substrate2can absorb light, so that the EPD can display black; and if the lower substrate2is transparent, the EPD is in a transparent state.

If the electrical field between the first wall electrode5and the second wall electrode6of at least one sub-pixel is greater than 0 and less than the critical value, as illustrated inFIG. 7, partial colored charged particles4in the at least one sub-pixel are disposed on the electrophoretic medium3. As for one pixel, if the same amount of colored charged particles4in the three sub-pixels of the pixel are disposed on the electrophoretic medium3, the pixel displays white; and if the amount of the colored charged particles4disposed on the electrophoretic medium3in the three sub-pixels of the pixel is not completely the same, the pixel achieves color display. When all the pixels display white, the EPD displays white; and when at least one pixel achieves color display, the EPD achieves color display. The amount of light reflected by the colored charged particles4in the sub-pixels may be adjusted by adjusting the magnitude of the electrical field between the first wall electrodes5and the second wall electrodes6of the sub-pixels within a range of greater than 0 and less than the critical value, so that the pixels can display different colors.

The critical value is the magnitude of the electrical field when all the colored charged particles4are just migrated to the first wall electrode5or the second wall electrode6and may be set according to the electricity quantity of the colored charged particles4, the quantity of the colored charged particles4, the size of the sub-pixel, and other factors. No limitation will be given here. In addition, description is given above to the means of achieving color display in the EPD by only taking the EPD with specific structure as an example. The means of achieving color display when the EPD has other specific structures can be obtained by those skilled in the art on the basis of the above content. No further description will be given here.

Illustratively, the sub-pixel in the second EPD is not only provided with the colored charged particles4but also provided with black charged particles8; charges of the black charged particles8and charges of the colored charged particles4are of different types; the density of the colored charged particles4is greater than that of the electrophoretic medium3; and the density of the black charged particles8is less than that of the electrophoretic medium3. The means of achieving color display in the EPD is as follows:

If there is no electrical field between all the first wall electrodes5and all the second wall electrodes6, as illustrated inFIG. 8, all the black charged particles8are disposed on the electrophoretic medium3and all the colored charged particles4are disposed beneath the electrophoretic medium3, so that all the colored charged particles4are shielded by the black charged particles8, and hence the EPD displays black.

If the electrical fields between all the first wall electrodes5and all the second wall electrodes6is greater than the critical value, as illustrated inFIG. 9, all the colored charged particles4and all the black charged particles8are respectively disposed on the first wall electrodes5and the second wall electrodes6, so that the display effect of the EPD depends on the structure of the lower substrate2. If, as illustrated inFIG. 9, the lower substrate2includes a transparent base substrate21and a light absorbing layer disposed on the base substrate21, the lower substrate2can absorb light, and hence the EPD can display black; and if the lower substrate2is transparent, the EPD is in a transparent state.

If the electrical field between the first wall electrode5and the second wall electrode6of at least one sub-pixel is greater than 0 and less than the critical value, as illustrated inFIG. 10, partial colored charged particles4in the at least one sub-pixel are not shielded by the black charged particles8and can reflect light. As for one pixel, if the same amount of colored charged particles4in the three sub-pixels of the pixel can reflect light, the pixel displays white; and if the amount of the colored charged particles4capable of reflecting light in the three sub-pixels of the pixel is not completely the same, the pixel achieves color display. When all the pixels display white, the EPD displays white; and when at least one pixel achieves color display, the EPD achieves color display. The amount of light reflected by the colored charged particles4in the sub-pixels may be adjusted by adjusting the magnitude of the electrical field between the first wall electrodes5and the second wall electrodes6of the sub-pixels within a range of greater than 0 and less than the critical value, so that the pixels can display different colors.

The critical value is the magnitude of the electrical field when all the colored charged particles4are just migrated to the first wall electrode5or the second wall electrode6and may be set according to the electricity quantity of the colored charged particles4, the quantity of the colored charged particles4, the size of the sub-pixel, and other factors. No limitation will be given here.

The application claims priority to the Chinese patent application No. 201610070530.2, filed Feb. 1, 2016, the entire disclosure of which is incorporated herein by reference as part of the present application.