Method for manufacturing a light emitting display
The invention relates to a method for manufacturing a light emitting display on a substrate comprising the steps of depositing a first electrode layer on or over the substrate, forming a plurality of light emitting layer segments on or over at least a part of the first electrode layer, applying at least one protective layer on or over at least one of the light emitting layer segments and depositing a second electrode layer. By providing a protective layer over the light emitting layer segments more freedom with regard to processing conditions is obtained in depositing and/or patterning of subsequent layers, since the susceptible light emitting layer segments are protected by the protective layers.
The invention relates to a method for manufacturing a light emitting display on a substrate.
The invention further relates to a light emitting display and to an electric device comprising such a display.
U.S. Pat. No. 5,962,970 discloses a method for manufacturing an organic display panel wherein first display electrodes, organic function layers including at least one organic electroluminescent medium formed on exposed portions of the first display electrodes and second display electrodes formed on the organic function layers are deposited on a substrate. Electrically insulating ramparts projecting from the substrate to a height up to 0.5 μm are employed for electrically disconnecting the adjacent second display electrodes, which are deposited by evaporation of a metal.
However, this method for manufacturing a light emitting display has several disadvantages relating to e.g. the use of the electrically insulating ramparts. One of these disadvantages is the limitation on the thickness for the second electrode as a result of which the electrical resistance of this second electrode is high. Moreover, the ramparts cause problems in sealing or encapsulating the light emitting display from environmental influences resulting in expensive sealing arrangements. Further the ramparts may be unstable leading to requirements for careful handling of the structures. Also processing flexibility for the light emitting display has some limitations due to the susceptibility of the light emitting layer segments of the display.
It is an object of the invention to provide an improved method for manufacturing a light emitting display wherein at least one of the above mentioned disadvantages is avoided or at least reduced.
This object is achieved by providing a method for manufacturing a light emitting display on a substrate comprising the steps of:
-
- depositing a first electrode layer on or over said substrate;
- forming a plurality of light emitting layer segments on or over at least a part of said first electrode layer;
- applying at least one protective layer on or over at least one of said light emitting layer segments;
- depositing a second electrode layer.
The invention further relates to a light emitting display comprising:
-
- a substrate;
- a first electrode layer deposited on or over said substrate;
- a plurality of light emitting layer segments formed on or over said first electrode layer;
- at least one protective layer applied on or over at least some of said light emitting layer segments;
- a second electrode layer.
By providing a protective layer over the light emitting layer segments more freedom with regard to processing conditions is obtained in depositing and/or patterning of subsequent layers, since the susceptible light emitting layer segments are protected by the protective layers. Processing using wet etching means can e.g. be performed for structuring of layers applied after the appliance of the protective layer. Preferably the light emitting layer segments are entirely covered by the protective layer.
In a preferred embodiment of the invention the protective layer comprises or consists of molybdenum or titanium. Molybdenum or titanium layers or layers comprising these materials are suitable to protect the light emitting layer segments for wet etching means.
In a preferred embodiment of the invention the second electrode layer is aluminium and/or is patterned by photolithography and subsequent etching. Patterning of the second electrode layer by such a process has become possible by the application of the protective layer on the light emitting layer segments, protecting the susceptible segment from e.g. wet etching agents. Thus, the prior art electrically insulating ramparts do not have to be applied for patterning the second electrode layer as a result of which the thickness of this second electrode layer can be significantly increased. A thick second electrode layer, larger than 0.5 μm, and preferably in the range of 0.5 to 3 μm, leads to a low electrical resistance and a short RC-time, which is important for high switching frequencies. Moreover the shape of the prior art ramparts provided problems with regard to obtaining an appropriate sealing film for encapsulating the structure. Photolithographic patterning of the second electrode layer provides an appropriate starting point, e.g. a smooth surface, for further encapsulation of the light emitting device.
In an embodiment of the invention the patterned second electrode layer comprises recesses wherein the protective layer is removed. A sealing film for encapsulation of the resulting structure is preferably deposited on the patterned second electrode layer and in the recesses. The sealing film can be made thin, e.g. 0.5 μm, in contrast to the typically applied thick encapsulation arrangements using e.g. individual metal caps for each structure or light emitting device on the display with a thickness in the range of 0.3 to 1 mm. The individual metal caps are typically glued to the substrate and comprise a getter material. The approach according to this embodiment enables encapsulation of substantially all the structures of the display without using a getter material, resulting in a considerable cost efficiency.
It should be appreciated that the previous embodiments, or aspects thereof, may be combined.
The invention further relates to an electric device comprising a light emitting display as described in the previous paragraph. Such an electric device may relate to handheld devices such as a mobile phone, a Personal Digital Assistant (PDA) or a portable computer as well as to devices such as a Personal Computer, a television set or a display on e.g. a dashboard of a car.
WO 00/16938 discloses a method for manufacturing a colour organic light emitting device structure, wherein a passivation layer permitting lithographic patterning of colour changing media using wet processing methods is employed. However, this passivation layer is deposited over the second electrode layer of the OLED drivers integrated in the substrate.
U.S. Pat. No. 5,998,926 discloses a method for manufacturing an organic electroluminescent device wherein the cathode is formed into a fine pattern by photolithography. However, the cathode layer is deposited directly on the substrate and is patterned before the organic electroluminescent layer is provided.
The invention will be further illustrated with reference to the attached drawing, which shows a preferred embodiment according to the invention.
In
A first electrode layer 2, commonly referred to as the anode, is deposited on or over the substrate 1, e.g. by vacuum evaporation or sputtering. The first electrode layer can subsequently be patterned by photolithography. Preferably the first electrode layer 2 is transparent with respect to the light to be emitted by the light emitting layer segments in operation of the light emitting display 14. For example, a transparent hole-injecting electrode material, such as Indium-Tin-Oxide (ITO), is used. Conductive polymers such as a polyaniline (PANI) and a poly-3,4-ethylenedioxythiophene (PEDOT) are also suitable transparent hole-injecting electrode materials. Preferably, a PANI layer has a thickness of 50 to 200 nm, and a PEDOT layer 100 to 300 nm.
In
In
In
In
However, the fluid light emitting substance of light emitting element or layer segment 7R should not flow to an adjacent light emitting element or layer segment 7B comprising a light emitting of different colour. It is illustrated that this effect is achieved by employing hydrophobic barriers as repellent parts 6.
In
In
In
In
In
In
In
For the purpose of teaching the invention, a preferred embodiment of a method for manufacturing a light emitting display has been described above. It will be apparent for the person skilled in the art that other alternative and equivalent embodiments of the invention can be conceived and reduced to practice without departing from the true spirit of the invention, the scope of the invention being only limited by the claims.
Claims
1. Method for manufacturing a light emitting display on a substrate comprising the steps of:
- depositing a first electrode layer on or over said substrate;
- forming a plurality of light emitting layer segments on or over at least a part of said first electrode layer;
- applying at least one protective layer on or over at least one of said light emitting layer segments;
- depositing a second electrode layer.
2. Method according to claim 1, wherein said first electrode layer is deposited on or over said substrate and comprises a material transparent to the light to be emitted by said light emitting layer segments in operation of the light emitting display.
3. Method according to claim 1, wherein said protective layer comprises molybdenum or titanium.
4. Method according to claim 1, wherein said second electrode layer is patterned by applying photolithography and subsequent etching in correspondence to said light emitting layer segments.
5. Method according to claim 4, wherein said second electrode layer is patterned such that it comprises recesses outside the areas comprising said light emitting layer segments, beneath which recesses said protective layer is substantially removed.
6. Method according to claim 5 wherein said patterned second electrode layer and said recesses are covered by at least one sealing film.
7. Method according to claim 1, wherein said second electrode layer has a thickness larger than 0.5 μm and preferably between 0.5 μm and 3 μm.
8. Light emitting display comprising:
- a substrate;
- a first electrode layer deposited on or over said substrate;
- a plurality of light emitting layer segments formed on or over said first electrode layer;
- at least one protective layer applied on or over at least some of said light emitting layer segments;
- a second electrode layer.
9. Light emitting display according to claim 8, wherein said protective layer comprises molybdenum or titanium.
10. Light emitting display according to claim 8, wherein said second electrode layer has a thickness between 0.5 μm and 3 μm.
11. Light emitting display according to claim 8, wherein said second electrode layer is patterned in correspondence with said light emitting layer segments and said patterned second electrode layer is covered by at least one sealing film.
12. Electric device comprising a light emitting display according to one of the claims 8-11 and/or manufactured according one of the claim 1-7.
Type: Application
Filed: Sep 12, 2003
Publication Date: Jul 13, 2006
Inventor: Antonius Nellissen (Eindhoven)
Application Number: 10/530,497
International Classification: H05B 33/14 (20060101);