This application claims the benefit of Taiwan Patent Application Serial No. 094142597, filed Dec. 2, 2005, the subject matter of which is incorporated herein by reference.
(1) Field of the Invention
The present invention relates to a dual emission display, more particularly, to a dual emission display having organic light emitting diodes mounted on two surfaces of the same one substrate.
(2) Description of the Prior Art
As the electric products are getting more and more various, they emphasize two display screens. For example, a mobile phone having a dual emission display can display a main function menu at one side, and display time at the other side. Typically, the dual emission display includes two adhered single-side panels, such as a liquid crystal panel adhered to an organic electro-luminescent panel, two adhered liquid crystal panels, or two adhered organic electro-luminescent panels.
As stated above, the dual emission display 10 has two package lids 115 and 125, and two transparent substrates 111 and 121. Therefore, it becomes larger, thicker, and heavier, so as not to meet the requirement in weight, thickness and size. Besides, the two display panels 11 and 12 are respectively manufactured in two different processes. Therefore, the fabrication of the dual emission display 10 is complicated and time-consuming. Another drawback is that the two display panels 11 and 12 need to be driven independently.
It is difficult to reduce the thickness because the typical dual emitting device has more complicated manufacturing process and more package lids and substrates.
The first object of the present invention is to provide a dual emission display, on different sides of which there are light emitting areas with the same size or not, and elements in alignment with each other or not.
The second object of the present invention is to provide a thinner dual emission display adapted to simpler fabricating process.
Accordingly, the dual emission display includes a substrate whose upper surface has a first organic light emitting diode, and whose lower surface has a second organic light emitting diode. The first organic light emitting diode and the second organic light emitting diode are respectively covered with a first protecting layer and a second protecting layer to isolate moisture and oxygen.
The organic light emitting diodes on lower or upper surfaces of the substrate are connected to an image controller through a conductive wire, so as to display images on two sides of the dual emission display independently. The structure of the dual emission display may be fabricated by evaporating on two sides of the substrate simultaneously, or in different stages. Therefore, the light emitting areas on different sides of the dual emission display are not limited to the same size, but arranged with light emitting elements independently. The result structure is thinner than the typical dual emission display, and is adapted to simpler fabricating process.
The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which
The protecting layer 24 may include one single layer or a plurality of sub-layers. The sub-layers include at least one inorganic material, such as aluminum oxide, silicon nitride, silicon oxide, silicon carbonate and diamond-like carbon etc. Preferably, the protecting layer 24 includes a complex structure consisting of a polymer film 241, a silicon oxygen film 242 and a silicon nitride film 243. Likewise, the protecting layer 25 may be a single-layer or multi-layer structure, and made of the same materials as or different materials from the protecting layer 24. The protecting layers 24 and 25 require 30 percent or above of light transmission to cover the light exit surface of the dual emission display 20.
The bonding zone 26 has bonding pads or conductive wires (not shown) to electrically connect to image controllers 27 such as scan drivers, data drivers or to bond with flexible printed circuits (FPCS, not shown). The elements on the upper and lower surfaces of the substrate 21 may be controlled by the same image controller 27, or different image controllers 27. Therefore, the dual emission display 20 can display the same images or different images simultaneously on its two sides.
The fabricating process of the second embodiment is described in detail. The reflective electrode 223, the organic emission layer 222 and the transparent electrode 221 are formed on the upper surface of transparent substrate 21 to construct the organic light emitting diode 22. The reflective electrode 233, the organic emission layer 232 and the transparent electrode 231 are formed on the lower surface of the transparent substrate 21 to construct the organic light emitting diode 23. The polymer layers 241 and 251 are formed on the transparent electrodes 221 and 231 of the organic light emitting diodes 22 and 23, respectively. The oxide layers 242 and 252 are evaporated on the polymer layers 241 and 251. The nitride layers 243 and 252 are evaporated on the oxide layers 242 and 252. The image controller 27 is connected to the substrate 21 via a conductive wire. Each above-mentioned layer can be formed by screen printing or organic vapor phase deposition (OVPD). In addition, it is available to evaporate at two sides of the substrate 21 simultaneously.
Above organic light emitting light diode can be a polymer organic light emitting diode (Polymer OLED) or a small molecular organic light emitting diode (SMOLED) which feature in electroluminescent. The reflective electrodes 223 and 233 can be metal electrodes formed on the substrate 21, so the light is reflected not to enter the substrate 21. The reflective electrode and the transparent electrode are not limited to be anode or cathode. By the way, the reflective electrodes 223 and 233 are interposed with a deep color or black insulating layer or replaced with a black electrode, or added with anti-reflective or light-absorbing materials for improving the anti-reflective ability and avoiding the leakage of light.
A hole or electron passing area is placed between the electrodes and the light emitting layer. In the hole passing area, a hole injecting layer (not shown) or a hole transporting layer (not shown) is interposed selectively. In the electron passing area, an electron injecting layer (not shown) or an electron transporting layer (not shown) is interposed selectively.
The electron transporting layer may be made of (8-hydroxyquinolinolato) aluminum (Alq), 1,3,5-Tris (N-phenylbenzimidazol-2-yl)benzene(TPBI), derivatives of anthracene, or derivatives of fluorine, spirofluorine etc., mixed with n-type dopant such as alkali halides, alkaline-earth halides, alkali oxides or metal-carbonate compound etc. to increase electron mobility thereof.
The electron injecting layer may be made of metal compound with work function perfectly adapted to that of the non-transparent electrode, such as alkali halides, alkaline-earth halides, alkali oxides or metal-carbonate compound, or an organic layer mixed with such n-type dopants.
The hole transporting layer may be made of allylamine group material such as N,N-di(naphthalene-1-yl)-N,N-diphenyl-benzidene (NPB).
The hole injecting layer may be made of allylamine group material, or phthalocyanine group material such as CuP.
The transparent electrode may be made of metal or transparent conductive materials such as ITO, IZO etc. The transparent substrate may be made of glass or plastic. The dual emission displays description in the present invention can be combined with the drivers such as thin film transistors, so they can be formed as active or passive displays.
In comparison with the prior art, the present invention has advantages of fewer substrates, more flexible arrangement of light emitters, thinner panel, simpler fabricating process and preferred moisture and oxygen resistance.
While the preferred embodiments of the present invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the present invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the present invention.
Number | Date | Country | Kind |
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94142597 | Dec 2005 | TW | national |