WO2010089684A1

WO2010089684A1 - Electroluminescent device

Info

Publication number: WO2010089684A1
Application number: PCT/IB2010/050380
Authority: WO
Inventors: Herbert F. Boerner
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N. V.
Priority date: 2009-02-05
Filing date: 2010-01-28
Publication date: 2010-08-12
Also published as: TW201037873A

Abstract

The invention relates to an electroluminescent device (10) comprising a substrate and on top of the substrate a substrate electrode, a counter electrode and an electroluminescent layer stack with at least one organic electroluminescent layer (50) arranged between the substrate electrode (20) and the counter electrode (30), and an encapsulation means (90) encapsulating at least the electroluminescent layer stack, the electroluminescent device (10) comprises at least one contact means (60), for electrically contacting the counter electrode (30) to an electrical source. To achieve the object of the invention, the contact means (60) is conductive glue, applied to the counter electrode (30).

Description

ELECTROLUMINESCENT DEVICE

FIELD OF THE INVENTION

This invention relates to an electroluminescent device according to the preamble of the claim 1, comprising a substrate and on top of the substrate a substrate electrode, a counter electrode and an electroluminescent layer stack with at least one organic electroluminescent layer arranged between the substrate electrode and the counter electrode, and an encapsulation means encapsulating at least the electroluminescent layer stack, the electroluminescent device comprises at least one contact means, for electrically contacting the counter electrode to an electrical source. Furthermore, the invention relates to a method for electrically contacting an electroluminescent device according to claim 10.

BACKGROUND OF THE INVENTION

In the WO 2007 / 013 001 A2 an organic light emitting diode (OLED) is described. The organic light emitting diode consists of a thin layer of approximately 100 nm of organic substances, sandwiched between two electrodes. The electrode layers normally possess a thickness approximately equal to the thickness of the organic substance. When a voltage - typically between 2 and 10 volts - is applied between the two electrodes, the organic substances emit light. Unfortunately, due to its small thickness the resistance of such electrodes is high, so that it is difficult to achieve a homogeneous distribution of the voltage over an area of the electrode. To eliminate this disadvantage, conducting posts are applied to the counter electrode of the OLED in the international patent application mentioned above. These conducting posts are connected to an encapsulation means, encapsulating the stack of layers formed by the electrodes and the electroluminescent layer. Unfortunately, the organic layers and the counter electrode are very sensitive. Therefore, connecting the conducting posts with the counter electrodes often leads to shorts. These shorts may for example emerge due to local destruction of the soft organic layers, bringing the counter electrode and the substrate electrode into direct contact.

SUMMARY OF THE INVENTION

Thus, the invention has for its object to eliminate the above mentioned disadvantages. In particular, it is an object of the invention to disclose a simplified and durable contacting of the counter electrode.

This object is achieved by an electroluminescent device as taught by claim 1 of the present invention. Also the object is achieved by a method as taught by claim 10 of the present invention. Advantageous embodiments of the electroluminescent device and the method are defined in the sub claims. Features and details described with respect to the electroluminescent device also apply to the method and vice versa.

This invention discloses that the contact means is conductive glue, applied to the counter electrode. The leading idea of the present invention is to use conductive glue to contact the counter electrode, as conductive glue is soft in its initial state so it can be applied to the counter electrode without exerting locally high pressure on the counter electrode. Therefore there is no risk that a short between the counter electrode and the substrate electrode develops during application of the glue. This leads to the advantage that the three-dimensional contact schema shown in the above mentioned international patent application can be modified in a way that the average life of a standard OLED can be achieved, by reducing the risk of shorts.

Usually, conductive glues consist of organic glue with conductive filler in the form of conductive flakes or particles. During setting, some glues display a certain shrinkage, which may force some of the filler particles into the underlying layers, creating shorts between substrate and counter electrode. To prevent this, it is advantageous to use glue with a lesser shrinkage and a higher elasticity like silicones and /or to make the counter electrode thicker. A thickness of the counter electrode of 0.5 to 30 micron is usually preferred, more preferred is a thickness between 0.75 and 20 micron, most preferred a thickness between 1 and 10 micron, to prevent filler particles from causing shorts.

A further advantage achieved by the usage of conductive glue as a contact means is, that a substrate with only one contiguous electrode can be used, which serves as a substrate electrode for the electroluminescent device. In known OLEDs, the electrode on the substrate is at least structured into two electrically separate regions: one serving as the substrate electrode and the other one connected to the counter electrode. Thus both the substrate and the counter electrode are led in one plane to the rim of the substrate, where they can be contacted by standard means. The disadvantage of this 2-dimensional contacting scheme is that the substrate electrode as well as the counter electrode have to share the periphery of the OLED for contacting, so that the electrode on the substrate needs to be divided into at least two disjoint regions (substrate electrode and second electrode to be contacted with the counter electrode) to avoid shorting the device. The disclosed 3- dimensional contacting eliminates this serious disadvantage of the 2-dimensional contacting. In a preferred embodiment the conductive glue comprises a matrix and filler. Preferably, the conductive glue comprises organic materials as the matrix and inorganic materials as the filler. In one embodiment, the conductive glue may comprise at least one of the following matrices: epoxies, polyurethanes or silicones. The filler and/or the matrix have to be conductive to conduct the electrical current from the electrical source to the counter electrode.

Therefore, it is preferred, that the conductive glue and/or the filler comprise conductive flakes or particles. The filler particles must possess low resistance, stability and durability. Therefore, it is preferred that the filler comprises flakes or particles of at least one: Silver, Gold, Nickel, Platinum, Copper, Palladium or other metals or other nonmetals like Carbon, glassy Carbon, Graphite, Carbon nanotubes, doped ZnO, SnO, electrically conductive nitrides, electrically conductive borides, metal covered glass or plastic beads, metal covered glass or plastic hollow beads or metal or graphite particles covered with copper, gold or silver.

In the context of the invention the notion electroluminescent (EL) layer stack denotes all layers prepared between the substrate electrode and the counter electrode. In one embodiment of an EL layer stack, it comprises at least one light emitting organic electroluminescent layer prepared between substrate and counter electrode. In other embodiments the layer stacks may comprise several layers prepared between substrate and counter electrode. The several layers may be organic layers, such as one or more hole transport layers, electron blocking layers, electron transport layers, hole blocking layers, emitter layers or a combination of organic and non-organic layers. The non-organic layers may be additional electrodes in case of two or more light emitting layers within the layer stack and/or charge injection layers. In a preferred embodiment the substrate electrode and or the counter electrode comprise at least one of the following materials: ITO, aluminum, silver, doped ZnO or an oxide layer. In the context of the invention the notion substrate denotes a base material onto which the different layers of an electroluminescent device are deposited. Normally, the substrate is transparent and is made of glass. Furthermore, it may be preferable that the substrate is transparent, preferably comprising at least one of the following materials: silver, gold, glasses or ceramics. It may also be a transparent polymer sheets or foils with a suitable moisture and oxygen barrier to essentially prevent moisture and/or oxygen entering the electroluminescent device layer stack. It is also possible to use non-transparent materials like metal foils as substrate. The substrate may comprise further layers, e.g. for optical purposes like light out-coupling enhancement or other purposes. The substrate is usually flat, but it may also be shaped into any three-dimensional shape that is desired. In the context of the invention the notion substrate electrode denotes an electrode deposited on top of the substrate. Usually it consists of transparent ITO (Indium- Tin oxide) optionally with an undercoating of SiO₂ or SiO to suppress diffusion of mobile atoms or ions from the glass into the electrode. For a glass substrate with an ITO electrode, the ITO is usually the anode, but in special cases it can also be used as the cathode. In some cases, thin Ag or Au layers (8-15 nm thick) are used single or in combination with ITO as the substrate electrode. If a metal foil is used as the substrate, it takes also the role of the substrate electrode, either anode or cathode. The notation on-top-of denoted the sequence of the listed layers. This notation explicitly comprises the possibility of further layers in between the layer denoted as on top of each other. For example, there might be additional optical layers to enhance the light out-coupling arranged between substrate electrode and substrate.

In the context of the invention the notion counter electrode denotes an electrode away from the substrate. It is usually non-transparent and made of Al or Ag layers of sufficient thickness such that the electrode is reflecting (typically 100 nm for Al and 100-200 nm for Ag). It is usually the cathode, but it can also be biased as the anode. For top-emitting or transparent electroluminescent devices the counter electrode has to be transparent. Transparent counter electrodes are made of thin Ag or Al layers (5-15 nm) or of ITO layers deposited on top of the other previously deposited layers.

In the context of the invention an electroluminescent device with a combination of a transparent substrate, a transparent substrate electrode and a non- transparent counter electrode (usually reflective), emitting the light through the substrate is called "bottom-emitting". In case of electroluminescent device comprising further electrodes, in certain embodiments both substrate and counter electrodes could be either both anodes or both cathodes, when the inner electrodes as driven as cathodes or anodes. Furthermore, in the context of the invention an electroluminescent device with a combination of a non-transparent substrate electrode and a transparent counter electrode, emitting the light through the counter electrode is called "top-emitting".

In the context of the invention the notion transparent electroluminescent device denotes an electroluminescent device, where the substrate, the substrate electrode, the counter electrode and the encapsulation means are transparent. Here the electroluminescent device is both, bottom and top-emitting. In the context of the invention a layer, substrate or electrode is called transparent if the transmission of light in the visible range is more than 50%; the rest being absorbed or reflected. Furthermore, in the context of the invention a layer, substrate or electrode is called semi-transparent if the transmission of light in the visible range is between 10% and 50%; the rest being absorbed or reflected. In addition, in the context of the invention light is called visible light, when it possesses a wavelength between 450 nm and 650 nm. In the context of the invention light is called artificial light, when it is emitted by the organic electroluminescent layer of the electroluminescent device. Furthermore, in the context of the invention a layer, connector or construction element of an electroluminescent device is called electrically conducting if its electrical resistance is less than 100000 Ohm. In the context of the invention passive electronic components comprise resistors, capacitors and inductivities. Furthermore, in the context of the invention active electronic components comprise diodes, transistors and all types of integrated circuits.

In the context of the invention a layer, substrate, electrode or a construction element of an electroluminescent device is called reflective if light incident on its interface is returned according to the law of reflection: the macroscopic angle of incidence equals the macroscopic angle of reflection. Also the term specular reflection is used in this case. Furthermore, in the context of the invention a layer, substrate, electrode or a construction element of an electroluminescent device is called scattering if light incident on it is not returned according to the law of reflection: macroscopic angle of incidence is not equal to the macroscopic angle of the returned light. There is also a distribution of angles for the returned light. Instead of scattering, the term diffuse reflection is also used. In a preferred embodiment the conductive glue is anhydrous and/or water free. In the context of the invention, the notion water free and/or anhydrous describes the fact, that no degradation due to water content during the average lifetime of an electroluminescent device can be observed by the naked eye. A visible degradation of the organic electroluminescent layer due to water diffusing into the layer stack can take the form of growing black spots or shrinkage of the emissive region from the edges. The notion water free and/or anhydrous not only depends on the conductive glue itself but also on the amount of water, which can be absorbed by the organic electroluminescent layer without damaging it.

In a further preferred embodiment the electroluminescent device may comprise moisture and/or oxygen barriers. In the context of the invention layers prevention harmful diffusion of moisture and/or oxygen into the layer stack are called moisture and/or oxygen barriers. A diffusion is denoted as harmful if a significant life-time reduction of the emitted light can be observed. Standard OLED devices according to state of the art achieve shelf life times in the order of 100000 hours or more. A significant reduction denotes a reduced life-time of about a factor of 2 or more. The electroluminescent device according to the invention comprises an encapsulation means to encapsulate the electroluminescent layer stack. The encapsulation means may also encapsulate the whole stack of layers of the electroluminescent device or just a plurality of layers, forming a part of the whole stack of layers. Preferably, the encapsulation means is a gas-tight element, covering at least the organic electroluminescent layer and the counter electrode. By using a gas-tight encapsulation means, it is prevented that environmental factors like water, or oxygen can damage the encapsulated layers. The encapsulation means may form a gas-tight lid. This lid may be formed of glass or metal. It is also possible to form the encapsulation means by one or a plurality of layers applied to the electroluminescent device or just parts of it. The layers may comprise silicon, silicon oxide, silicon nitride, aluminum oxide or silicon oxinitride. All the named encapsulation means prevent mechanical and/or environmental factors from affecting the layer stack of the electroluminescent device adversely.

As an example, the encapsulation means can be made of metals, glass, ceramics or combinations of these. It is attached to the substrate by conductive or non- conductive glue, melted glass frit or metal solder. Therefore, it may also provide mechanical stability for the electroluminescent device.

In a preferred embodiment, the encapsulation means is electrically connected to the contact means. The electrical connection between the contact means and the encapsulation means may be direct or indirect. In a direct manner, the encapsulation means has direct contact with the conductive glue of the contact means. In the indirect manner, a means like a wire may be used to connect the encapsulation means and the conductive glue of the contact means. Apart from the named wire other means may be used to connect the encapsulation means and the contact means, which are known to a person skilled in the art. It is possible to connect the electroluminescent device to an electrical source with the help of the encapsulation means. Therefore, a wire etc. may be attached to the encapsulation means, which transfers the electrical current via the conductive glue of the contact means to the counter electrode. A requirement for this embodiment is that the encapsulation means is at least conductive in one part. To prevent shorts, the encapsulation means has then to be insulated against the substrate electrode. This may be realized in such a way that the encapsulation means is divided in two areas. One of them is an electrically conductive contact area and one is an electrically insulating area. The encapsulation means has to be designed in such a way, that the electrically conductive contact area is connected to the conductive glue of the contact means. This embodiment has the advantage that during production the conductive glue can easily be applied between the counter electrode and the encapsulation means. If the amount of conductive glue is too large for the gap between the counter electrode and the contact area of the encapsulation means it will flow sideways when the encapsulation means is placed on top of the substrate with the layer stack and therefore it will just cover a larger area than that of the encapsulation means. However, the amount of applied glue must be limited in order not to provide an electrical contact to the substrate electrode by flowing over the sides of the layer stack. In another embodiment, it is preferred that the counter electrode is only touched by the conducting glue, otherwise the electroluminescent layer stack and/or the organic electroluminescent layer and the counter electrode could be damaged leading to a short between the counter electrode and the substrate electrode.

In another preferred embodiment the encapsulation means comprises an electrically conductive gas-tight feed through. This gas-tight feed through comprises a conductive element, which is connected to the connection means. This may be done by direct contact with the conductive glue or by help of a wire or an element known to a person skilled in the art. If the encapsulation means is electrically conductive and connected to the substrate electrode it is preferred that the gas-tight feed through is electrically insulated against the encapsulation means. This may be done by an insulation means in which the conductive element is embedded. This insulation means for the gas- tight feed through may for example be formed by glass or ceramic, encasing the conductive element.

In another preferred embodiment the encapsulation means comprises an electrically conductive contact area. In this embodiment the encapsulation means consists of two different elements, one forming the contact area and another one forming an insulating area. Preferably, the contact area is arranged on top of the encapsulation means. Alternative, the contact area may be formed by an element embedded in the encapsulation means, wherein this embedded element is conductive. For example a metal disk may be embedded in a gas-tight multilayer structure, forming the encapsulation means. This metal disk then forms the contact area, which is in electrical contact with the contact means of the electroluminescent device. Preferably, the contact area is electrically insulated against the encapsulation means. This may be done by embedding the contact area in glass or ceramic or another material known to a person skilled in the art.

In a preferred embodiment the electroluminescent device comprises at least one protective means, wherein the protective means a. is arranged on the substrate electrode and is electrically non-conductive, and b. is at least fully covering the area below the contact means.

This includes the possibility that the protective means may further extend over the area of the contact means. During setting, some glues display a certain shrinkage, which may force some of the filler particles into the underlying layers, creating shorts between substrate and counter electrode. If no restriction on the type of glue is desired, and if the counter electrode cannot be made thicker, a protective means is applied to the substrate electrode to prevent a possible short due to the conductive glue. The use of at least one protective means makes the electroluminescent device completely insensitive to the specific properties of the conductive glue. Therefore, all known conductive glues can be used for contacting the counter electrode to an electrical source. The protective means has to cover the full area where the contact means is applied to the counter electrode, since this might be the source of shorts, but it could also be larger than the area of the contact means. To prevent a direct contact between the counter electrode and the substrate electrode, it is preferable that the protective means has a thickness and/or a hardness, which assure that the contact means cannot get into electrical contact with the substrate electrode. To achieve this aim, the protective means may comprise non-conductive glue and/or a photo resist and/or a lacquer and/or paint and/or layer of glass, made of re-melted glass frit. The protective means may also comprise an oxidized metal layer like anodized Aluminum.

People skilled in the art may choose other electrically non-conductive materials within the scope of this invention.

The protective means must have properties that on the one hand ensure that it is electrically not conductive. Furthermore, it must be thick and / or hard enough to shield the substrate electrode from the contact means. The precise thickness and hardness depend on the actual pressure exerted by the contact means, but typically 1-100 micrometer thickness are sufficient. The desired protection has been achieved with photoresist layers of 1.5 micrometer thickness as well as with layers of non-conductive glue of 10-200 micrometer thickness, but thicker layers can also be used. Furthermore, it must be ensured that the protective means does not damage either the substrate electrode, the organic electroluminescent layer or the counter electrode. In preferred embodiment the protective means comprises non-conductive glue. Furthermore, it is preferable that the non-conductive glue of the protective means is anhydrous and/or water free.

To achieve a lasting non-conductive glue at least one of the following matrices may be used: epoxys, polyurethanes, acrylic or silicone. As disclosed a protective means may comprise non-conductive glue. This non-conductive glue may be transparent, opaque or comprise scattering properties. Depending on the material used for the protection means, experiments have shown that the area to which the protection means is applied may appear dark at normal operation of the electroluminescent device, since direct current injection from the counter electrode to the substrate electrode is blocked. Therefore, another preferred embodiment is characterized in that the protective means comprises at least one scattering means, for scattering light generated by the organic electroluminescent layer; preferably that the scattering means is embedded in the protective means. This scattering means scatters and or reflects part of the artificial light guided by the substrate. This results in a brightening of the otherwise non- emissive area. As the substrate often works as a kind of light guide, the scattering means of the protective means enables this light to be scattered and reflected out of the electroluminescent device. The scattering means may be formed by a plurality of pigments and/or flakes embedded in the protective means. This pigments and/or flakes may for example comprise: aluminum, mica effect pigments, titan dioxide particles or other flakes or particles known to a person skilled in the art as scattering and/or reflecting the artificial light of the organic electroluminescent device.

In another preferred embodiment the protective means is dyed. This may be done by coloring the protective means itself or by applying colored pigments to the protective means. In another embodiment the protective means is arranged as a closed contour having an inner edge and an outer edge framing the electroluminescent layer stack, wherein the counter electrode partly covers the closed contour establishing a contiguous gap between the outer edge of the contour and the edge of the counter electrode sufficiently large to isolate the counter electrode from the substrate electrode. With such a closed contour, the manufacturing effort can be further reduced by applying the same mask for depositing the electroluminescent layer stack and the counter electrode. Applying the same mask for the deposition of electroluminescent layer stack and counter electrode without a non-conducting closed contour on top of the substrate electrode framing said layer stack, it would be very likely, that both electrodes are in electrical contact somewhere at the edge of the counter electrode. In this embodiment, the isolation between substrate and counter electrode is maintained by the contiguous gap between counter electrode and the outer edge of the contour of the non-conducting protection means.

To achieve a homogeneous distribution of the voltage across the area of the counter electrode it is preferred, that a plurality of contact means are applied to the counter electrode to improve the current distribution uniformity over the counter electrode. By using a number of contact means, the achieved distribution of the voltage is more homogeneous. As the contact means is formed by conductive glue it is easy to apply a plurality of contact means - for example drops of conductive glue - to the counter electrode. These drops of conductive glue may be in direct contact with the encapsulation means. Therefore, to connect the electroluminescent device to an electrical source it is just needed to connect the encapsulation means to the electrical source. The encapsulation means will most probably have a resistance, which is orders of magnitude smaller than those of the counter electrode. Therefore, all contact means will be connected to the same potential. This leads to a uniform distribution of voltage and current to the organic electroluminescent layer and in a homogeneous generation of artificial light by the organic electroluminescent layer. The number of contact means applied to the counter electrode depends on the one hand on the resistance of the counter electrode and on the other hand on the size of the counter electrode. For known electroluminescent devices it has shown to be preferable that the following numbers of contact means are applied to the counter electrode: 2, 4, 5, 8, 16 or 32. In another preferred embodiment the counter electrode is structured into a plurality of electrically disconnected counter electrode segments, wherein each counter electrode segment comprises at least one contact means. As described above, there exists a plurality of embodiments how to connect the contact means of each counter electrode segment to the electrical source. For example the encapsulation means may comprise a plurality of gas-tight feed troughs, each connected to one contact means. Therefore, a user of the electroluminescent device may have the ability to individually connect each gas- tight feed through to an electrical source. In an alternative embodiment the contact means may have direct contact to the encapsulation means and/or separated conductive contact areas of the encapsulation means. A user would then just have to connect the encapsulation means and/or the separated conductive contact areas to an electrical source, to feed the layer stack.

The object of the present invention is also achieved by a method for electrically contacting an electroluminescent device, wherein the electroluminescent device comprises an electroluminescent layer stack with at least one organic electroluminescent layer arranged between a substrate electrode and a counter electrode on top of a substrate and an encapsulation means encapsulating at least the electroluminescent layer stack, the method comprising the step: applying at least one contact means to the counter electrode, for electrically contacting the counter electrode to the electrical source, wherein the contact means comprises a conductive glue. Features and details described with respect to the electroluminescent device also apply to the method and vice versa. The advantage of the disclosed method is that to contact the electroluminescent device conductive glue is used. This conductive glue prevents any mechanical damage of the counter electrode or short.

Another preferred embodiment of the method comprises the step: adding a protective means to the substrate electrode, wherein the protective means a. is arranged on the substrate electrode and is electrically non- conductive, and b. is at least fully covering the area below the contact means.

The protective means is a layer which protects the organic layers and the counter electrode against any negative effect from the contact means by insulating the substrate electrode reliably towards the counter electrode. Thus, even if the contact means may damage the counter electrode and the organic layers no short will occur, as the protective means prevents any direct contact between the two electrodes. The protective means may comprise non-conductive glue or photoresist. The area of the protective means may extend beyond the area of the contact means. The disclosed electroluminescent device described above is preferably connected in accordance with at least one of the methods described above.

The invention also discloses the use of conductive glue for contacting a counter electrode of an electroluminescent device. The advantage of using conductive glue compared to the known means used for contacting the counter electrode is that the probability of a short between the counter electrode and the substrate electrode is reduced.

The invention also discloses the use of a protective means for preventing shorts between the substrate electrode and a counter electrode, provided with at least one contact means. The protective means is arranged on the substrate electrode and therefore prevents a direct contact between the substrate electrode and the counter electrode, even if the contact means penetrates part of the counter electrode and the organic layers.

The invention also relates to a substrate covered by a single, contiguous, non-structured electrode to be used as a substrate electrode in an electroluminescent device according to our present invention. The term "non- structured" denotes any substrate electrode, where the substrate area coated with the substrate electrode is not adapted to apply a second conductive area onto the substrate within the encapsulated area of the substrate area of an organic electroluminescent device covered by an encapsulation means, which is electrically isolated to the substrate electrode.

To produce the disclosed electroluminescent device of the invention, the different layers of the layer stack are deposited onto the substrate. After depositing the substrate electrode onto the substrate, the protective means may be applied to the substrate electrode. Afterwards, the organic layers are deposited. Finally, the counter electrode is deposited. According to the state of the art, the preferred deposition technology for the organic layers and the counter electrode is vacuum evaporation. Vacuum evaporation is a deposition technology, where the materials to be deposited follow a straight path from the evaporation source to the substrate, leading to a directed deposition. If the protective means has steep edges or overhanging edges, shadowing effects will occur, which lead to holes in the organic layers and the counter electrode. To prevent this undesirable effect, it is preferable that the protective means has smooth and non-steep edges. Therefore, the invention also claims a protective means comprising material properties and / or application procedures that prevents the emergence of a shadowing edge on a substrate electrode. In a preferred embodiment the material property preventing the emergence of a shadowing edge is the viscosity, e.g. the viscosity at enhanced temperature. Preferably the viscosity is low. If non-conductive glue is used as protective means it may be applied like a drop onto the substrate electrode. If this non-conductive glue of the protective means comprises a viscosity that enables it to flow, a smooth hill- like shape of the protective means will result, which prevents shadowing effects. If a material is used for the protective means that gives rise to steep edges that may create shadowing effects if only one deposition source is used, several deposition sources could be used to deposit material from different directions onto the substrate. It may also be advisable to rotate or otherwise move the substrate during deposition to ensure a continuous layers deposition over the protective means.

The aforementioned electroluminescent device and/or method, as well as claimed components and the components to be used in accordance with the invention in the described embodiments are not subject to any special exceptions with respect to size, shape, material selection. Technical concepts such that the selection criteria are known in the pertinent field can be applied without limitations. Additional details, characteristics and advantages of the object of the present invention are disclosed in the subclaims and the following description of the respective figures - which are an exemplary fashion only - showing a plurality of preferred embodiments of the electroluminescent device according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the invention will be described with respect to the following figures, which show:

FFiigg.. 11 a first embodiment of an electroluminescent device according to the invention,

Fig. 2 a top view of the electroluminescent device according to

Fig. 1,

Fig. 3 the electroluminescent device according to Fig. 1 with a protective means,

Fig. 4 a top view of the electroluminescent device according to

Fig. 3,

Fig. 5 another embodiment of the electroluminescent device,

Fig. 6 the electroluminescent device according to Fig. 5 with a protective means,

Fig. 7 the electroluminescent device with a gas-tight feed through,

Fig. 8 the electroluminescent device according to Fig. 7 with a protective means,

Fig. 9 the electroluminescent device with an electrically conductive contact area,

Fig. 10 the electroluminescent device according to Fig. 9 with a protective means,

Fig. 11 the electroluminescent device with a plurality of contact means, FFiigg.. 1122 a top view of the electroluminescent device according to

Fig. 11,

Fig. 13 the electroluminescent device according to Fig. 11 with protective means,

Fie. 14 a top view of the electroluminescent device according to Fig. 13, Fig. 15 a top view of the electroluminescent device with a segmented counter electrode, Fig. 16 the electroluminescent device according to Fig. 15 with electrically conductive contact areas,

Fig. 17 the electroluminescent device according to Fig. 16 with Protective means,

Fig. 18 the electroluminescent device according to Fig. 16 with another embodiment of the protective means, Fig. 19 a top view of the electroluminescent device according to

Fig. 18, and Fig. 20 the electroluminescent device with the protective means and the contact means.

Fig. 21 the electroluminescent device with protective means arranged as a closed contour framing the electroluminescent layer stack as a side view. Fig. 22 the electroluminescent device with protective means arranged as a closed contour framing the electroluminescent layer stack as a top view of Fig.21.

DETAILED DESCRIPTION OF EMBODIMENTS

In Figure 1 an electroluminescent device 10 according to a first embodiment of the invention is shown. The electroluminescent device comprises a substrate electrode 20, a counter electrode 30 and an organic electroluminescent layer 50 as the electroluminescent layer stack in this and the following examples. The organic electroluminescent layer 50 is arranged between the substrate electrode 20 and the counter electrode 30 forming a layer stack. This layer stack is arranged on a substrate 40. In the shown embodiment the substrate electrode 20 is formed by an approximately 100 nm thick layer of ITO, which is a transparent and conductive material. Onto this substrate electrode 20 the organic electroluminescent layer 50 is deposited. If a voltage is applied between the substrate electrode 20 and the counter electrode 30 some of the organic molecules within the organic electroluminescent layer 50 are exited, resulting in the emission of artificial light, which is emitted by the electroluminescent layer 50. The counter electrode 30 is formed by a layer of aluminum, working as a mirror reflecting the artificial light through the substrate electrode 20 and the substrate 40. To emit light into the surrounding, the substrate 40 in this embodiment is made of glass. Thus, the electroluminescence device according to fig. 1 is a bottom emitting OLED. The electroluminescence device 10 shown in the following figures as well as its components and the components used in accordance with the invention are not shown true to the scale. Especially the thickness of the electrodes 20, 30, organic electroluminescence layer 50 and substrate 40 are not true to the scale. All figures just serve to clarify the invention. As can be seen in Figure 1 the organic electroluminescent layer 50 and the counter electrode 30 are encapsulated by an encapsulation means 90. This encapsulation means 90 comprises a lid- like shape. Furthermore, the electroluminescent device 10 comprises at least one contact means 60, for electrically contacting the counter electrode 30 to an electrical source. The contact means 60 is therefore a part of the path leading from the counter electrode 30 to the electrical source. In the known prior art contact posts are used as contact means, which are applied to the counter electrode 30. Such contact posts have the disadvantage that they are mechanically applied to the counter electrode and often lead to shorts between the counter electrode 30 and the substrate electrode 20. To overcome this disadvantage the invention discloses that the contact means 60 is conductive glue, applied to the counter electrode 30. Conductive glue can be applied in a gentle manner to the counter electrode 30 so that there is no damage to the counter electrode 30 and the organic electroluminescent layer 50 and/or the electroluminescent layer stack leading to a short between the two named electrodes 30, 20. In Figure 1 the contact means 60 is in direct contact with the counter electrode 30 as well as with the encapsulation means 90. Therefore, it is easy to electrically connect the counter electrode 30 to an electrical source. The user just has to apply an electrically conductive means to the encapsulation means 90, which then bridges the gap to the contact means 60 formed by conductive glue. The conductive glue then leads the electrical current to the counter electrode 30. In the shown embodiment the encapsulation means 90 is on the one hand connected to the substrate electrode 20 and on the other hand in contact with the conductive glue of the contact means 60. To prevent a short at least a part of the encapsulation means 90 and/or the encapsulation means 90 as a whole must be insulated against the substrate electrode 20. In the shown embodiment a top 95 of the encapsulation means 90 is electrically conductive, whereas a side 96 of the encapsulation means 90 is electrically insulating. Therefore, a short between the counter electrode 30 and the substrate electrode 20 is prevented. Depending on the type of use the encapsulation means 90 may possess the following properties:

Property of the top 95 of Property of the side 96 of encapsulation means 90 encapsulation means 90

1. conductive conductive

2. insulating conductive

3. conductive insulating

4. insulating insulating

In the first case the encapsulation means 90 must be insulated against the substrate electrode 20. Therefore, an insulating rim 94 - shown in Figure 5 - must be applied to the encapsulation means 90. In the third case there would be no need for any insulating rim 94, as the side 96 of the encapsulation means 90 insulates the conductive top 95 against the substrate electrode 20. In the second case an electrically conductive feed through may be applied to the isolating top 95 of the encapsulation means to connect it with the contact means 60. The same applies in the fourth case, in which in the side 96 as well as the top 95 of the encapsulation means 90 are insulating. The substrate electrode 20 is connected to a power source via the connection means 93'. Suitable connection means 93 'are known be people skilled in the art.

The encapsulation means 90 has to be gas-tight to prevent ambient atmosphere from damaging the organic electroluminescent layer 50 or any of the two electrodes 20, 30 encapsulated in the encapsulation means 90. The shown electroluminescent device 10 furthermore may comprise a getter 170 arranged within the encapsulation means 90. This getter 170 is used to absorb humidity or other damaging gases, which happens to diffuse into a protected area within the encapsulation means 90. The getter 170 may comprise CaO or Zeolites. Other materials are known to a person skilled in the art.

The Figure 2 shows a top view on the backside of the electroluminescent device 10 according to Figure 1. Therefore, the view is mostly directed onto the counter electrode 30. For easier understanding, the electroluminescence device 10 is shown without the encapsulation means 90. In Figure 2 a single contact means 60 is applied to a center of the area of the counter electrode 30. To depict the position of the contact means 60, the encapsulation means 90 is not shown in this Figure. A connection means 93' is applied to a rim of the substrate electrode 20. Current has to flow from the substrate electrode 20 through the organic electroluminescent layer 50 into the counter electrode 30 and finally through the contact means 60 back to the electrical source. As the resistance of a very thin layer of metal like the substrate electrode 20 and/or the counter electrode 30 is high, it might be appropriate to use more than one contact means 60 to achieve a homogenous generation of artificial light by the electroluminescent device 10.

Onto the substrate electrode a connection means 93 ' is applied. In all figures the connection means 93' of the substrate electrode 20 has the form of a wire attached to the substrate electrode 20. This should just symbolize the possibility to connect the substrate electrode 20 with the electrical source. Obviously the shown embodiment of the connection means 93 ' is just an exemplary design of such a connection means 93 ' . Other arrangements known to a person skilled in the art can also be used to connect the substrate electrode 20 to an electrical source.

To use any kind of conductive glue a preferred embodiment of the disclosed electroluminescent device 10 comprises a protective means 70. Figure 3 shows such an electroluminescent device 10. The protective means 70 is arranged on the substrate electrode 20 and is electrically non-conductive. Furthermore, it is arranged at least fully below the contact means 60, but may extend further. To prevent any occurrence of a short, the protective means 70 is arranged on the substrate electrode 20. Besides, the design and elements of the electroluminescent device 10 according to Figure 3 are identical to those of Figure 1.

The Figure 4 shows a view on the backside of the electroluminescent device 10 according to Figure 3. For easier understanding, the electroluminescence device 10 is shown without the encapsulation means 90. The protective means 70 is arranged on the substrate electrode 20 and electrically non-conductive. It is the aim of the protective means 70 to protect the substrate electrode 20 against any electrical contact with the contact means 60 or the counter electrode 30. To achieve this aim it is preferable that the protective means 70 has a thickness and/or a hardness, which assure that the contact means cannot get into electrical contact with the substrate electrode.

Therefore, protrusions of the contact means 60 penetrating through the counter electrode 30 and the organic electroluminescent layer 50 will not reach the substrate electrode 20. Rather than that, they will be stopped by the protective means 70. Alternative, the protective means 70 may comprise a size, which limits the probability that the contact means 60 is the source of any short between the counter electrode 30 and the substrate electrode 20. Results of tests have shown that surprisingly non-conductive glue is a well-suited material, to be used as protective means 70. Therefore, a drop of non- conductive glue may be applied to the substrate electrode 20, before the organic electroluminescent layer 50 and the counter electrode 30 are deposited onto the substrate 40. The Figure 4 shows the protective means 70 arranged beneath the organic electroluminescent layer 50 and the counter electrode 30. As can be seen, the protective means 70 is arranged below the contact means 60. Furthermore, the protective means 70 covers a protection area on a substrate electrode 20, which is larger than a connection area, covered by the contact means 60 on the counter electrode 20. Therefore, no influence of the connection means 60 to the counter electrode 20 and/or the organic electroluminescent layer 50 does lead to any kind of electrically conductive bridge to the substrate electrode 20. This is successfully prevented by the protective means 70.

In Figure 5 another embodiment of the disclosed electroluminescent device 10 is shown. Deviating from the electroluminescent device of Figure 1 and 3 the contact means 60 has no direct contact with the top 95 of the encapsulation means 90.

Rather than that, a connection means 93 is used. This connection means 93 may be a wire, but may also be any other means known by a person skilled in the art for bridging the gap between the conductive top 95 and the contact means 60. In the shown embodiment the top 95 as well as the side 96 of the encapsulation means 90 are electrically conductive. Therefore, the electroluminescent device 10 can be connected to an electrical source at any point of the encapsulation means 90. Due to its material property and/or size the encapsulation means 90 possesses a low resistance compared to the resistance of the counter electrode 30. Therefore, a user may take the most convenient section of the encapsulation means 90 to connect it to an electrical source. To prevent a short between the counter electrode 30 and the substrate electrode 20 an insulating rim 94 is applied to the electroluminescent device 10. This insulating rim 94 is arranged between the substrate electrode 20 and the side 96 of the encapsulation means 95. Therefore, there is no direct electrical contact between the substrate electrode 20 and the encapsulation means 90 nor the counter electrode 30.

The Figure 6 shows the electroluminescence device 10 as figure 5, only that a protective means 70 is applied to the substrate electrode 20. This protective means 70 again prevents any short between the two electrodes 20,30 due to any properties of the contact means 60. Besides, the design and elements of the electroluminescent device 10 according to Figure 6 are identical to those of Figure 5.

In Figure 7 yet another embodiment of the encapsulation means 90 is disclosed. In this embodiment the encapsulation means comprises an electrically conductive gas tight feed through 92. This feed through 92 is connected to the contact means 60. This might - as shown - be done by a connection means 93, which is connecting on the one hand the feed through 92 and on the other hand with the contact means 60. The connection means 93 may be a wire, a foil or another electrically conductive element known to a person skilled in the art. It might also be, that the feed through 92 is in direct contact with the contact means 60. So during the mounting of the encapsulation means 90 onto the layer stack, the gas tight feed through 92 might be pressed into the not dried conductive glue of the contact means 60. After hardening there is an electrical contact between the gas tight feed through 92 and the contact means 60. On the outside of the encapsulation means 90, the gas tight feed through 92 may be contacted to an electrical source. In the shown embodiment it is assumed that the encapsulation means 90 as a whole is electrically conductive. Therefore, it is appropriate that the gas tight feed through 92 comprises an insulation means 97. This insulating means 97 prevents any short between the feed through 92 - connected to the counter electrode 30 - and the encapsulation means 90 - connected to the substrate electrode 20. This insulating means 97 may be formed of ceramic, glass or made of remelted glass-frit. If there is no insulating means 97 for the gas tight feed through 92, the top 95 of the encapsulation means 90 may also be insulating. Thus, a short between the two electrodes 20,30 is also prevented.

The electroluminescence device 10 according to figure 8 is in accordance with the electroluminescence device 10 of figure 7, but a protective means 70 is applied. This protective means 70 is arranged at least fully below the contact means 60, but may extend further. In the shown embodiment the protective means 70 occupies a larger area on the substrate electrode 20 than the contact means 60 on the counter electrode 30. Besides, the design and elements of the electroluminescent device 10 according to Figure 8 are identical to those of Figure 7. In figure 9 another preferred embodiment of the electroluminescence device 10 is shown. This electroluminescence device 10 again comprises a stack of layers formed by the counter electrode 30, the organic electroluminescence layer 50 and a substrate electrode 20. On the backside of counter electrode 30 the contact means 60 is applied. This contact means 60 is electrically conductive glue applied to the counter electrode 30. The encapsulation means 90 comprises an electrically conductive contact area 100. As can be seen in figure 9 the conductive glue of the contact means 60 is in direct contact with the contact area 100 of the encapsulation means 90. The user of the electroluminescence device 10 according to figure 9 just has to connect the contact area 100 with an electrical source to generate artificial light. As the contact area 100 is more robust and larger than the contact means 60 and/or the counter electrodes 30 the connection to the electrical source can easily be done with known means. For example a wire can be welded to the contact area 100 of the encapsulation means 90. The contact area 100 may be formed by a metal disk embedded into the encapsulation means 90. This metal disk is electrically conductive and may therefore be used as a bridge between the contact means 60 and the electrical source. In the shown embodiment the encapsulation means 90 is positioned onto the substrate electrode 20 and also electrically conductive. To prevent a short, the encapsulation means 90 comprises an insulating border 101, which encircles the contact area 100. This prevents any direct contact between the contact area 100 and the top 95 of the encapsulation means 90. Apart from the shown embodiment, the contact area 100 may not only be formed by a disk embedded in the encapsulation means 90. It might also be, that the encapsulation means 90 is a one piece element, which is partially doped with conductive particles, so that the conductive area 100 is formed. In this embodiment the rest of the encapsulation means, which is not conductive, insulates the contact area 100 against the substrate electrode 20.

Figure 10 also shows the electroluminescence device 10 with a contact area 100 as described in figure 9. This electroluminescence device 10 also comprises the protective means 70 applied to the substrate electrode 20. All other features of the electroluminescence device 10 are in correspondence with electroluminescence device 10 according to figure 9.

In figure 11 an electroluminescent device 10 with two contact means 60 can be seen. The conductive glue of the contact means 60 fills the gap between the counter electrode 30 and the encapsulation means 90. The contact means 60 extends towards the top 95 of the encapsulation means 90. In the shown embodiment the top 95 and the side 96 of the encapsulation means 90 are electrically conductive. Therefore, it is easy to connect the counter electrode 30 to an electrical source. The encapsulation means 90 can be connected in known manner to an electrical source. Due to the fact, that four contact means 60 are used to contact the counter electrode 30, a homogenous distribution of the voltage across the counter electrode 30 is achieved. This will result in a homogenous generation of artificial light by the organic electroluminescence layer 50. As the encapsulation means 90 as a hole is conductive, an insulating rim 94 has to be arranged between the encapsulation means 90 and the substrate electrode 20. This ensures that no short occurs.

The Figure 12 shows a top view of the electroluminescent device 10 according to Figure 1. Here four contact means 60 are applied to the counter electrode 30. Each of these contact means 60 comprises conductive glue. With the help of these four contact means 60 a more homogenous distribution of the voltage and/or the current in the electroluminescent device 10 may be achieved. For easier understanding, the electroluminescence device 10 in figure 12 is shown without the encapsulation means 90. In figure 13 the electroluminescence device 10 of figure 11 is shown with protective means 70. As can be seen each of the contact means 60 possesses its own protective means 70. The protective means 70 are arranged beneath the contact means 60, which can also be seen in Figure 14 that shows a view on the counter electrode 30 of the electroluminescent device 10. For easier understanding, the electroluminescence device 10 in figure 14 is shown without the encapsulation means 90. All other features of the electroluminescence device 10 are in correspondence with electroluminescence device 10 according to figure 11. In another preferred embodiment the counter electrode 30 is structured into a plurality of electrically separated counter electrode segments 31. This is illustrated by figures 15 to 19. In figure 15 a top view on an electroluminescence device 10 is shown. For easier understanding the electroluminescence device 10 is shown without the encapsulation means 90. As can be seen the counter electrode 30 is separated into four segments 31, which are not electrically connected, as can be seen from figure 16. Each segment 31 of the counter electrode 30 possesses its own contact means 60. Figure 16 shows that the conductive glue of the contact mean 60 is applied in such a way, that it has direct contact to the encapsulation means 90. The encapsulation means 90 possesses for each of the contact means 90 one contact area 100. These contact areas 100 are electrically conductive and can be used to feed the layer stack with electrical current. As the encapsulation means 90 is directly mounted on the substrate electrode 20 each of the contact area 100 possesses an insulating border 101 to prevent a short. A user of the shown electroluminescence device 10 is able to individually connect each contact area 100 to an electrical source. Therefore, it is possible to activate just parts of the electroluminescence device 10. Depending on the counter electrode segment 31, which is supplied with electrical current, only the part of the organic electroluminescence layer 50 under this counter electrode segment will emit artificial light.

In figure 17 an electroluminescence device 10 with a subdivided counter electrode 30 is shown. Compared to the electroluminescence device 10 of figure 16, the shown electroluminescence device 10 comprises protective means 70. As can be seen, each of the contact means 60 possesses its own protective means 70 arranged on the substrate electrode 20. Each of the electrically non-conductive means 70 prevents shorts. All other features of the electroluminescence device 10 are in correspondence with electroluminescence device 10 according to figure 16. Figure 18 shows the same electroluminescence device 10, but this time, the protective means 70 is designed in a way, that it is arranged beneath two contact means 60. Therefore, not only one small protective means 70 is applied to the counter electrode. If for example non-conductive glue is used for the protective means 70, it can be applied bank- like onto the substrate electrode 20. It is therefore easier to apply to the substrate electrode 20 and can be used to protect the electroluminescence device 10 against shorts for a plurality of contact means 60. Furthermore, it is preferable that the protective means 70 comprises at least one scattering means 180, for scattering a light, generated by the organic electroluminescent layer 50. The scattering means 180 may comprise and/or be pigments and/or particles. This prevents that the area beneath the protective means 70 might appear darker than its surrounding. These scattering means 180 may comprise mica or aluminum flakes or a material with a high refractive index like TiO₂ particles. The scattering means 180 also reflect parts of the artificial light and/or of visible light guided in the substrate 40, and therefore brightens the otherwise non-emissive layer beneath the protective means 70. All other features of the electroluminescence device 10 are in correspondence with electroluminescence device 10 according to figure 17.

The Figure 19 shows a top view of the electroluminescent device 10 according to Figure 18. Here four contact means 60 are applied to the counter electrode 30. Beneath two contact means 60 a single elongated protective means 70 is shown. For easier understanding, the electroluminescence device 10 in figure 19 is shown without the encapsulation means 90.

In figure 20 a part of the electroluminescence device 10 is shown. The figure 20 is a magnification of the layer stack. It shall be noticed, that the size of the layers are not true to the scale. Onto the substrate 40 the substrate electrode 20 is deposited. Onto this substrate electrode 20 the protective means 70 is arranged. The protective means 70 is covered by the organic electroluminescence layer 50 and the counter electrode 30. Onto this organic electroluminescence layer 50 the counter electrode 30 is deposited. To connect the counter electrode 30 to an electrical source the contact means 60 is applied to the counter electrode 30. In the shown embodiment the contact means 60 is conductive glue and the protective means 70 comprises non-conductive glue. The different electrodes 20, 30 and the electroluminescence layer 50 are applied in layers to the substrate 40. After applying the substrate electrode 20, the protective means 70 has to be deposited onto the substrate electrode 20. The protective means 70 has to have material properties and/or application procedure that prevents the emergence of a shadowing edge on the substrate electrode 20. In a preferred embodiment the material property is low viscosity. Therefore, the material forming the protective means will flow on the substrate electrode 20, forming a hill-like structure with smooth slopes. There will be no shadow edges, which could prevent a continuous coverage of the organic electroluminescence layer 50 and the counter electrode 30. The protective means 70 preferably has a lower viscosity at enhanced temperature that enables a two step application. In a first step the material forming the protective means - like non-conductive glue - is applied to the substrate electrode 20 in the desired position. Then the substrate is heated to an enhanced temperature. Due to its lower viscosity, the material of the protective means 70 will then flow out on the substrate electrode. Preferably the material of the protective means 70 comprises a viscosity that enables it to flow slowly, to form a protective means 70 with a defined thickness and smooth slopes. As the temperature of the protective means and/or the material of the protective means decreases, it should solidify, to form the protective means 70. This ability and/or material property of the protective means to flow onto the substrate electrode 20 in such a way, that no shadowing edges are formed enables the manufacturing of the disclosed electroluminescence device 10.

In an experiment, the protective means was made of a two-component epoxy glue (UHU plus schnellfest, curing time 5 min). The binder and the hardener were mixed in the prescribed ratio of 1 : 1 and then applied at room temperature to the ITO- covered glass substrate in one spot. Then the substrate was heated on a hot plate to 60° C for 15 min, which allowed the glue first to flow into a smooth hill and then to solidify rapidly. The procedure was carried out in a glove box in dry Nitrogen atmosphere (less than 1 ppm of water). The substrate with the hardened protective means was then introduced into a vacuum chamber and the organic layers and the counter electrode were deposited. The finished device was then encapsulated with a glass cover lid having a hole at the position of the protective means. The cover was applied by UV curing glue. A getter for water was placed in the cavity formed by the substrate and the lid. In a last step, conductive glue (Circuitsworks conductive epoxy CW2400 from Chemtronics Inc.) was applied though the hole in the cover lid to the counter electrode at the position of the protective means and a brass plate with a small brass spring was attached with two component epoxy to the cover lid, closing the hole in the cover lid in such a way that the brass spring was embedded in the conductive glue. After setting of all glues (appr. 1 hour), the OLED was reliably driven by connecting the plus lead of a power supply to the rim of the substrate where the substrate electrode was exposed and the minus lead to the brass plate on the cover lid. The electroluminescent layer stack and the counter electrode made of Aluminum covered the protective means without cracks or holes. At the position of the protective means, there was no light emission.

In a second experiment, the binder of the glue was mixed with TiO₂ particles, leading to a white substance. The rest of the procedure followed exactly the description give above. After setting of all glues (appr. 1 hour), the OLED was reliably driven by connecting the plus lead of a power supply to the rim of the substrate where the substrate electrode was exposed and the minus lead to the brass plate on the cover lid. The electroluminescent layer stack and the counter electrode made of Aluminum covered the protective means without cracks or holes. At the position of the protective means, there was no light emission due to the scattering of the light guided in the substrate by the TiO₂ particles embedded in the glue.

Fig. 21 and 22 show the electroluminescent device with a protection means 70 arranged as a closed contour with an outer edge 71 on top of the substrate electrode 20. Fig.22 is the top view of the electroluminescent device of fig.21 shown in a side view. The protection means 70 is at least partly covered by the counter electrode 30 establishing a contiguous gap 72 between the edge of the counter electrode 30 and the outer edge 71 of the closed contour of the protection means 70. Since there is no direct contact between counter electrode 30 and substrate electrode 20 and the closed contour of the protection means 70 is made of electrically non-conducting material, both electrodes 20, 30 are isolated against each other. The organic electroluminescent layer 50 fully covers the substrate electrode 30 inside the closed contour and extend partly on top of the protection means 70, preferably forming the same gap between the edge of the organic electroluminescent layer 50 and the outer edge 71 of the closed contour of the protection means 70. The contact means 60 is applied at an area of the counter electrode 30, where a protection layer is located fully below the contact means 60. In Fig. 22, only the non- covered area of the closed contour is visible. The closed contour 70 further extends below counter electrode 30 and contact means 60 as shown in Fig. 21. The closed contour enables the application of the same mask for depositing the electroluminescent layer stack and the counter electrode. The described embodiments comprise as an example an organic electroluminescent layer 50 within the layer stack. In alternative embodiments within the scope of this invention, the electroluminescent layer stack may comprise layer additional to organic electroluminescent layer 50 such as whole transport layers, hole blocking layers, electron transport layers, electron blocking layers, charge injection layers further conducting layers etc.

LIST OF NUMERALS:

10 electroluminescent device

20 substrate electrode

30 counter electrode

31 counter electrode segments

40 substrate

50 organic electroluminescent layer

60 contact means

70 protective means

71 outer edge of the protective means as a closed contour

72 contiguous gap between edge of counter electrode and outer edge of the closed contour

90 encapsulation means

92 a gas tight feed through

93,93' connection means

94 insulating rim

95 top of encapsulation means

96 side of encapsulation means

97 insulating means for gas tight feed through 92

100 contact area

101 insulating border for contact area 100

170 getter

180 scattering means

Claims

CLAIMS:

1. An electroluminescent device (10) comprising a substrate and on top of the substrate a substrate electrode, a counter electrode and an electroluminescent layer stack with at least one organic electroluminescent layer (50) arranged between the substrate electrode (20) and the counter electrode (30), and an encapsulation means (90) encapsulating at least the electroluminescent layer stack, the electroluminescent device (10) comprises at least one contact means (60), for electrically contacting the counter electrode (30) to an electrical source, characterized in that the contact means (60) is conductive glue, applied to the counter electrode (30).

2. Electroluminescent device (10) according to claim 1, characterized in that the conductive glue is anhydrous and/or water free.

3. Electroluminescent device (10) according to any preceding claims 1 or 2, characterized in that the encapsulation means (90) is electrically connected to the contact means (60).

4. Electroluminescent device (10) according to any preceding claims, characterized in that the encapsulation means (90) comprises an electrically conductive gas tight feed through (92); preferably that the gas tight feed through (92) is electrically insulated against the encapsulation means (90).

5. Electroluminescent device (10) according to any preceding claims, characterized in that the encapsulation means (90) comprises an electrically conductive contact area (100); preferably that the contact area (100) is electrically insulated against the encapsulation means (90).

6. Electroluminescent device (10) according to any preceding claims, characterized in that the electroluminescent device (10) comprises at least one protective means (70), wherein the protective means (70) a. is arranged on the substrate electrode (20) and is electrically non- conductive, and b. is at least fully covering the area below the contact means (60)

7. Electroluminescent device (10) according to claim 6, characterized in that the protective means (70) comprises at least one scattering means (180), for scattering light, generated by the organic electroluminescent layer (50); preferably that the scattering means (180) is embedded in the protective means (70).

8. Electroluminescent device according to claim 5 or 6, characterized in that the protective means (70) is arranged as a closed contour having an inner edge and an outer edge (71) framing the electroluminescent layer stack, wherein the counter electrode (30) partly covers the closed contour (70) establishing a contiguous gap (72) between the outer edge (71) of the contour (70) and the edge of the counter electrode

(30) sufficiently large to isolate the counter electrode (30) from the substrate electrode (20).

9. Electroluminescent device (10) according to any preceding claims, characterized in that a plurality of contact means (60) are applied to the counter electrode (30) to improve the current distribution uniformity over the counter electrode (30), preferably that the following number of contact means (60) are applied to the counter electrode (30): 2, 4, 5, 8, 16 or 32,.

10. Electroluminescent device (10) according to any preceding claims, characterized in that the counter electrode (30) is structured in a plurality of electrically separated counter electrode segments (31), wherein each counter electrode segment

(31) comprises at least one contact means (60).

11. Method for electrically contacting an electroluminescent device (10), wherein the electroluminescent device (10) comprises an electroluminescent layer stack with at least one organic electroluminescent layer (50) arranged between a substrate electrode (20) and a counter electrode (30) on top of a substrate and an encapsulation means (90) encapsulating at least the electroluminescent layer stack, the method comprising the step: applying at least one contact means (60) to the counter electrode (30), for electrically contacting the counter electrode (30) to the electrical source, wherein the contact means (60) comprises a conductive glue.

12. Method according to claim 11, characterized in that the method further comprises the step: adding a protective means (70) to the substrate electrode (20), wherein the protective means (70) a. is arranged on the substrate electrode (20) and is electrically non- conductive, and b. is at least fully covering the area below the contact means (60).

13. Use of conductive glue for contacting a counter electrode (30) of an electroluminescent device (10).

14. Use of a protective means (70) for preventing a short between a substrate electrode (20) and a counter electrode (30), provided with at least one contact means

(60).

15. Protective means (70) comprising a material property, that prevents the emergence of a shadowing edge on a substrate electrode (20), preferably that the material property is the viscosity, preferably the viscosity at enhanced temperature.

16. A substrate covered by only one contiguous electrode to be used as the substrate electrode in an electroluminescent device according to claim 1.