Display devices like TFT-LCDs (thin film transistor liquid crystal displays) are used in laptop computers, and are also finding increasingly wider application in GSM (Global System for Mobile communications) telephones. In addition, other kinds of display devices instead of LCDs are being used in GSM telephones; for example, (polymer) LED display devices are being used. Apart from these types of displays, other display techniques, such as EWD devices suitable for flat plate displays are evolving. The electro-wetting functionality provides displays with excellent brightness and contrast, and relatively low power consumption compared to many other display technologies.
Referring to FIG. 5, a top plan diagram of a sub-pixel unit of a related art EWD device is shown. The sub-pixel unit 100 is rectangular, and is defined by two opposite long side walls 101 and two opposite short side walls 102. The long side walls 101 and the short side walls 102 are connected end-to-end, and are made from hydrophobic interfacial materials.
A thin film transistor element 121 is disposed at a corner of the sub-pixel unit 100. Another corner region of the sub-pixel unit 100 adjacent to the thin film transistor element 121 is defined as a first region 129. An area of the first region 129 is substantially two times an area of the thin film transistor element 121. A transparent electrode 122 is disposed in an entire area of the sub-pixel unit 100 except where the thin film transistor element 121 is located. A hydrophobic insulating layer (not shown), an oil layer (not shown), and a water layer (not shown) are positioned in that order on the thin film transistor element 121 and the transparent electrode 122.
An area of the sub-pixel unit 100 is defined as X. The area of the thin film transistor element 121 is defined as Y. The oil layer has more affinity to the long side walls 101 than to the thin film transistor element 121, thus the oil layer in the first region 129 is not apt to move to the thin film transistor element 121. When the sub-pixel unit 100 works in an on state, the oil layer is displaced so that it covers only the first region 129, and therefore the first region 129 is not transparent. Accordingly, an aperture ratio of the sub-pixel unit 100 is substantially (X−3Y)/X. This aperture ratio is rather low.
What is needed, therefore, is to provide an EWD device that can overcome the above-described deficiencies.