Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-04-24
2003-06-24
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C313S495000
Reexamination Certificate
active
06583584
ABSTRACT:
The invention relates to an electroluminescent device having at least two electroluminescent elements arranged on a substrate in accordance with a desired pattern, each element comprising a first and a second electrode layer and, disposed therebetween, an electroluminescent layer, the device comprising a partitioning relief pattern including partitioning ribs of an insulating material protruding from the substrate and forming enclosure areas for containing a liquid layer from which the electroluminescent layer is obtainable in accordance with the desired pattern.
The invention also relates to a method for manufacturing of an electroluminescent device having at least two electroluminescent elements, comprising the steps of;
providing a first electrode layer in accordance with a desired pattern on a substrate;
providing a partitioning relief pattern comprising partitioning ribs protruding from the substrate and forming enclosure areas in accordance with a desired pattern;
depositing a liquid layer in the enclosure areas of the partitioning relief pattern;
converting the liquid layer to an electroluminescent layer;
and providing a second electrode layer in accordance with a desired pattern on the electroluminescent layer.
An electroluminescent device according to the present invention can preferably be used as a monochrome or a multi-colour still image display or a matrix display of the passive or active type for displaying of variable still images or movable images.
An electroluminescent device and a method for manufacturing according to the introductory part, is disclosed e.g. in EP 880303, where the electroluminescent layer is obtained through inkjet printing on a substrate. To assist in that the inkjet printed liquid layer for each pixel will be restricted within the boundaries of each pixel, partitioning walls or banks are formed between adjacent pixels. This is advantageous especially in displays containing two or more colours to prevent mixing of the liquid for respective luminescent colour between adjacent pixels, and in this way it is possible to improve the contrast and brightness of the displayed image.
However, with a device and a method according to EP 880303, it is a clear risk that the electroluminescent liquid from one pixel will spill over and mix with the electroluminescent liquid in an adjacent pixel, which may be of different kind in order to display for instance different colours, if the pixels are filled with too large amounts of electroluminescent liquid.
For manufacturing reasons it is also advantageous to keep the partitioning ribs as low as possible but at the same time make the liquid layer with a sufficient layer thickness, due to poor concentration of active luminescent substance in the liquid, which often has not more than about 1% active substance. Hence, during the converting process through e.g. drying or gelling of the liquid layer, the remaining electroluminescent layer will be considerable reduced, typically in the order of one hundred times thinner than the liquid layer. Consequently it is desirable to fill the pixels with as much liquid as possible. This is discussed further in application EP 00/11706.
Moreover, during the manufacturing process, it is favourable to use inkjet printing devices or the like, with a multi nozzle head instead of a single nozzle head. In a multi nozzle head it is not possible to get exactly the same output of liquid from each nozzle but a variation of approximately 5-10% might normally be expected in the case of an inkjet printing device. If the inkjet head is tuned in such a way that the desired layer thickness is reached even with the nozzle with the lowest output quantity, it is a clear risk that the electroluminescent elements filled by the nozzles with the highest output quantity will spill over the partitioning ribs and the liquids in adjacent electroluminescent elements will mix.
It is an object of the invention to provide an electroluminescent device where the risk of mixing of the liquid layers between adjacent electroluminescent elements is reduced and, consequently, the electroluminescent elements may be provided with a thicker and more uniform electroluminescent layer and the performance of employing multi nozzle heads during manufacturing is improved. At least these objects are achieved with an electroluminescent device, according to the preamble, which is characterized in that a partitioning relief element separating adjacent electroluminescent elements comprises at least two partitioning ribs with an intermediate groove in the area between the partitioning ribs.
The invention also relates to a method of manufacturing of an electroluminescent device with essentially the same objects as for the electroluminescent device mentioned above. At least these objects are achieved through a method according to claim 6.
The invention is based on the insight that the above mentioned objects are achieved with an electroluminescent device and a method for manufacturing, where each electroluminescent element or pixel is provided with a separate partitioning rib which is not common for two adjacent pixels in the area between them. Instead there are at least two partitioning banks or ribs between adjacent pixels with a groove between the partitioning ribs of the respective adjacent pixels.
One requirement for an electroluminescent layer to emit light is that the electroluminescent layer is disposed between two electrodes, one cathode and one anode. Accordingly, in a preferred embodiment the partitioning groove between two adjacent pixels has not more than one electrode so that any electroluminescent liquid spilled over from one of the pixels into the groove, will not be energised and emit light with a disturbing effect on the image generated by the display.
The present invention is both suited for monochrome and for colour displays. For both types the invention will facilitate forming of a uniform electroluminescent layer. For colour displays is a further advantage that the invention will help to prevent mixing of different colours. A still further advantage is that with a method according to the invention it is possible to print more than one colour next to each other with a single printer, before drying of the colours and also at same time in one process.
There are various ways of arranging the electrodes and electroluminescent layers in a display. If for example the device is intended for simple illumination or displaying of a not variable, still picture image, both the anode and cathode may be common to the entire device, i.e. be applied in one continuous electrically conductive layer on respective sides of the electroluminescent layer. On the other hand, if the device is intended to display variable or moving pictures, each pixel need to be independently addressable. This can be achieved in basically two different ways.
Firstly the electrodes can be arranged in columns and rows, for instance are the anodes electrically connected in rows, whereas the cathodes are electrically connected in columns perpendicular to the anodes. This is called a passive matrix display and energising of a pixel is effected in the intersection of a voltage-fed anode row and a likewise voltage-fed cathode column. Normally, imaging is carried out through sequentially voltage feeding of the anode rows and simultaneous voltage feeding of the cathode columns whose intersections with the anode rows is desired to emit light. Accordingly the pixels will be energised intermittently.
Secondly the pixels can be individually and independently addressable, e.g. by controlling each pixel by means of a thin film transistor. This is called an active matrix display and in this way the pixels can, when desired, be energised continuously with a brighter image as a result.
In a preferred embodiment of the invention, the electroluminescent device is formed on a suitable substrate, of for instance transparent synthetic resin, quartz, ceramics or glass. The first electrode, preferably the anode, is applied in a thin layer on the substrate in the desired patt
Camps Ivo Godfried Jozef
De Koning Jochem Petrus Maria
Duineveld Paulus Cornelis
Liedenbaum Coen Theodorus Hubertus Fransiscus
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