Electrophoretic display device
View Patent ↗An electrophoretic display device includes a first substrate, a second substrate facing the first substrate, and a barrier electrode disposed between the first and second substrates to define a pixel. An electrophoretic material is placed in the pixel. The pixel includes a first pixel electrode and a second pixel electrode disposed on and insulated from the first pixel electrode. The electrophoretic material moves according to an electric field generated between the barrier electrode and the first pixel electrode and between the barrier electrode and the second pixel electrode, so that a plurality of gray scales is displayed through the pixel.
1. An electrophoretic display device comprising:
a first substrate;
a second substrate that faces the first substrate;
a barrier electrode disposed between the first substrate and the second substrate to define a pixel, the barrier electrode receiving a common voltage; and
an electrophoretic material disposed in the pixel, the electrophoretic material including a dielectric solvent and a plurality of electrophoretic particles distributed in the dielectric solvent, the pixel comprising:
a first pixel electrode;
a first thin film transistor that applies a first pixel voltage to the first pixel electrode;
a second pixel electrode disposed on the first pixel electrode and insulated from the first pixel electrode; and
a second thin film transistor that applies a second pixel voltage to the second pixel electrode,
wherein the barrier electrode is spaced from the second pixel electrode in a plan view of the electrophoretic display device.
2. The electrophoretic display device of claim 1 , wherein positions of the electrophoretic particles are controlled by an electric field generated between the barrier electrode and the first pixel electrode and between the barrier electrode and the second pixel electrode, and the pixel displays a plurality of gray scales corresponding to the positions of the electrophoretic particles.
3. The electrophoretic display device of claim 2 , wherein the electrophoretic particles have a positive polarity, and the pixel displays a lowest gray scale among the gray scales when the first pixel voltage and the second pixel voltage are lower than the common voltage.
4. The electrophoretic display device of claim 3 , wherein the second pixel voltage is lower than the first pixel voltage.
5. The electrophoretic display device of claim 2 , wherein the electrophoretic particles have a positive polarity, and the pixel displays a highest gray scale among the gray scale when the first pixel voltage and the second pixel voltage are higher than the common voltage.
6. The electrophoretic display device of claim 5 , wherein the second pixel voltage is higher than the first pixel voltage.
7. The electrophoretic display device of claim 2 , wherein the pixel displays gray scales between the lowest gray scale and the highest gray scale among the grays scales when the first pixel voltage and the second pixel voltage have different polarities from each other with respect to the common voltage.
8. The electrophoretic display device of claim 2 , wherein the electrophoretic particles have a negative polarity, and the pixel displays a lowest gray scale among the gray scale when the first pixel voltage and the second pixel voltage are higher than the common voltage.
9. The electrophoretic display device of claim 1 , wherein a center portion of the second pixel electrode overlaps a center portion of the first pixel electrode, and wherein the second pixel electrode is smaller than the first pixel electrode.
10. The electrophoretic display device of claim 9 , wherein the first pixel electrode comprises slits that surround the center portion of the first pixel electrode.
11. The electrophoretic display device of claim 10 , wherein the first pixel electrode comprises trunk portions that protrude from the center portion of the first pixel electrode and comprises branch portions that protrude from the trunk portions, and wherein the branch portions are alternately arranged with the slits.
12. The electrophoretic display device of claim 1 , further comprising a repelling electrode disposed on the second substrate to push out the electrophoretic particles from the second substrate.
13. The electrophoretic display device of claim 12 , wherein the repelling electrode receives a voltage having a same polarity as the electrophoretic particles.
14. The electrophoretic display device of claim 1 , wherein the first pixel electrode comprises an opening portion corresponding to the second pixel electrode.
15. The electrophoretic display device of claim 1 , wherein the pixel further comprises a storage electrode disposed at a lower portion of the first pixel electrode and insulated from the first pixel electrode while being overlapped with the first pixel electrode.
16. The electrophoretic display device of claim 1 , wherein the first pixel electrode comprises a cut-away portion, and the second pixel electrode and the second thin film transistor are electrically connected to each other by a connection electrode of which at least a portion is disposed in the cut-away portion.
17. The electrophoretic display device of claim 16 , wherein the cut-away portion extends to a center portion of the first pixel electrode from a side of the first pixel electrode, and the second pixel electrode is disposed on the center portion of the first pixel electrode.
18. The electrophoretic display device of claim 1 , wherein the pixel further comprises:
a third pixel electrode disposed to be spaced apart from the first pixel electrode; and
a third thin film transistor that applies a third pixel voltage to the third pixel electrode.
19. The electrophoretic display device of claim 18 , wherein the third pixel electrode is disposed on a same layer as the first pixel electrode.
20. The electrophoretic display device of claim 19 , wherein the third pixel electrode at least partially surrounds the first pixel electrode.