Electrowetting display is a technology in which the display effect is realized by using a non-polar liquid as it has the behaviors of “spreading and contracting” on a hydrophobic dielectric membrane. The principle of operation is as follows: when no voltage is applied to the assembly, the non-polar oil droplets have a greater affinity to the hydrophobic dielectric layer than the polar aqueous solution, which causes the oil droplets to be spreaded in a planar fashion over a surface of the hydrophobic dielectric layer, and when a voltage is applied to the assembly, a distribution of electric charges generated over the hydrophobic dielectric layer would increase its affinity to water such that the oil droplets are squeezed to a corner of pixels.
FIGS. 1 and 2, as shown, are principle diagrams of prior art applications of electrowetting display for a black-and-white display, which comprise from bottom up: a visible-light source 101, a lower substrate 102, a pixel electrode 103, a thin film transistor 104, an insulating layer 105, an oleophilic layer 106, a barrier 107, a black oil layer 108, deionized water 109, an upper substrate 110 and a common electrode 111. In FIG. 1, when no electric power is applied to the black oil layer 108, it is spreaded over the oleophilic layer 106 at this pixel zone, and a visible light emitted by the visible-light source 101 is incident on the black oil layer 108 and absorbed (as shown by the arrow in FIG. 1), thus leading to the display of a black state; in FIG. 2, the pixel electrode 103 supplies electric power to the black oil layer 108, upon which a distribution of electric charges is generated over the oleophilic layer 106 such that good affinity is formed between the water and the oleophilic layer 106 thus squeezing the black oil layer 108 to a corner of this pixel zone, i.e. at the barrier 107, and in this case, the visible light radiated to this pixel zone is not absorbed by the black oil layer 108, but instead reflected by a reflector to display a bright state (as shown by the arrow in FIG. 2).
The above principle of electrowetting display can only achieve a black-and-white display, whereas a colored display requires using a colored membrane, and this does not arrive at a desired colored display effect.