FR3101197A1 - Encapsulated Flexible Organic Light Emitting Diode - Google Patents

Abstract

The present invention relates to a flexible organic light emitting diode shown in Figure 1 comprising: A stack comprising an organic layer in contact with a first face of a first electrode 2, and in contact with a second face of a second electrode 7, A flexible support 1 of the stack in contact with the first electrode 2, A flexible cover 12 surmounting the second electrode 7 and comprising an external face 13 carrying at least one electrical contact pickup member 16 electrically connected to a given electrode among the first electrode 2 and the second electrode 7 by electrical connection means, characterized in that the electrical connection means comprise an exposed portion 17 along an edge of the cover 12 and an interconnection portion 18 extending, transversely to a dimension in thickness of the cover 12, between the contact recovery member 16 and the exposed portion 17

Description

encapsulated flexible organic light emitting diode

FIELD OF THE INVENTION

The present invention relates to the field of organic light-emitting diodes (OLEDs) in particular for lighting, OLEDs which, once powered by an electric current, emit their own light. The present invention also relates to a method for producing such an organic light-emitting diode on a flexible support encapsulated by a flexible PCB cover.

TECHNOLOGICAL BACKGROUND

The light-emitting diode, better known by the acronym LED in English for "Light Emitting Diode", is a semiconductor with physical properties such that the light-emitting diode has the ability to directly convert electricity into light, while being d unequaled efficiency in terms of energy consumption. Lighting by light-emitting diode allows a homogeneous diffusion of the light beam; this lighting is in particular very close to daylight.

It is these advantageous characteristics that have attracted designers to take an increasing interest in light-emitting diodes for automotive applications, for example, or in the field of lighting. These light sources also represent excellent opportunities for designers. These diodes can be of various shapes and large sizes.

Conventionally, an OLED comprises a stack of layers, with two electrodes, namely an anode and a cathode, and an intermediate part of organic material at the level of which the light is emitted during an electrical stress in the form of a potential difference between the two electrodes. Indeed, a recomposition of holes and electrons produces a photon emission at this level. This emission is propagated on one side of the OLED device, in particular by transmission through one of the two electrodes, then chosen to be sufficiently transparent in the band of wavelengths of light to be produced.

Such an organization has the advantage of generating only a very small overall thickness of the device. In addition to the issues of size and aesthetics, this low thickness allows mechanical stress contexts that are difficult to envisage on the basis of a light source of different technology. In particular, we are beginning to offer electronic devices for which the OLED(s) are carried by a support of a flexible nature, for example with a view to forming flexible digital display devices, or in other fields, in particular that of technical lighting (Automotive, Military, Medical, Aeronautics, …) with adapted 3D shapes.

If the organic layer allows such an emission of light, it does however have poor resistance in contact with water or oxygen. Contact of the organic layer with water or oxygen produces oxidation and leads to a loss of chemical properties and electroluminescent properties. The lifetime of an OLED is thus directly linked to the quality of the encapsulation necessary to protect it from contact with water and oxygen. The maximum admissible penetration rate of water, respectively oxygen, in an OLED is generally 10-6 g/m².day.atmosphere, respectively 10-4 cc/m².day.atmosphere. In order to achieve such rates, it is currently known to carry out a tight encapsulation of an OED, by protecting said OED by a hollow thick glass cover glued by an adhesive peripheral joint on a stack of layers comprising the organic layer, side opposite the substrate. The volume between the cover and the OLED includes an inert gas. This thick glass hollow hood system is not suitable for flexible OLED.

However, it is necessary to access the electrodes of an OLED in order to make the electrical contacts. For this, it is known to make a short cover leaving the electrical connectors accessible. Protective and encapsulation covers are often ultra-thin glass substrates with a thickness of less than 100 microns for better sealing and flexibility. In this case, access to the electrodes is provided through openings in the substrate. The ultra-thin glass substrate in production mode is often large in size. In this case, the openings in the glass can weaken the substrate which must undergo a complex process of cleaning and depositing layers of OLED. To overcome this problem, several substrates are used: mainly plastic. The plastic cover suffers from its poor sealing and temperature resistance.

Given the constraints linked to the process for manufacturing flexible light-emitting diodes, the present invention proposes to respond at least in part to the drawbacks of current techniques. According to one aspect, the invention allows efficient encapsulation while facilitating the electrical connection of the flexible OLED.

The present invention relates to an organic light-emitting diode comprising:

a stack comprising an organic layer in contact by a first face with a first electrode, and in contact by a second face with a second electrode,

a flexible support for the stack in contact with the first electrode,

a flexible cover surmounting the second electrode and comprising an outer face carrying at least one electrical contact recovery member electrically connected to a given electrode from among the first electrode and the second electrode by electrical connection means,

Advantageously, characterized in that the electrical connection means comprise a portion exposed along an edge of the cover and an interconnection portion extending, transversely to a thickness dimension of the cover, between the contact recovery member and the exposed portion .

The present invention also relates to a method for producing a flexible organic light-emitting diode comprising:

the formation of a stack on a flexible support, comprising successively and in order, the formation of a first electrode, the formation of an organic layer, the formation of a second electrode,

the covering of the stack by surmounting the second electrode with a flexible cover comprising an outer face carrying at least one electrical contact recovery member electrically connected to a given electrode among the first electrode and the second electrode by electrical connection means

characterized in that it comprises:

the formation of an exposed portion of the electrical connection means produced along a slice of the cover and of an interconnection portion extending, transversely to a thickness dimension of the cover, between the contact recovery member and the portion exposed.

Thus, it is possible to deport the place of the resumption of contact for the electrical connection of the flexible OLED to the outside, relative to a connection zone on the electrode. This area may be on the periphery of the OLED while the contact recovery member may be on the upper surface of the cover, for example. It is then possible to connect one and/or the other of the two electrodes from the upper face of the cover, at any location.

In this way, according to one aspect of the invention, a means is formed to access the electrodes of a flexible OED while providing an encapsulation that effectively protects the organic layer against contact with water and/or salt. 'oxygen. In addition to having access to the electrodes, it is possible to have an electrical connection located in a specific area to facilitate the addressing of the DELOs if there are several.

BRIEF INTRODUCTION OF FIGURES

Other characteristics, objects and advantages of the present invention will appear on reading the detailed description which follows, with reference to the appended drawings, given by way of non-limiting examples, and in which:

There illustrates an embodiment of the invention with resumption of contact by the periphery of the cover and organs of flexible & printed electronics;

There illustrates an embodiment of the invention with resumption of contact by the periphery of the cover and conductive layer;

There illustrates an embodiment of the invention with resumption of contact by holes in the cover and organs of flexible & printed electronics;

There illustrates an embodiment of the invention with contact recovery by holes in the cover and conductive layer.

For the sake of clarity, the elements in the figures are not drawn to scale.

DETAILED DESCRIPTION

It is specified that in the context of the present invention, the term “on” does not necessarily mean “in contact with”. Thus, for example, the deposition of a layer on another layer does not necessarily mean that the two layers are directly in contact with one another, but it does mean that one of the layers at least partially covers the another by being either directly in contact with it, or by being separated from it by a film, yet another layer or another element.

It is also specified that a layer can comprise a plurality of layers. On the other hand, the term "layer" does not necessarily mean a full plate distribution on the substrate.

Before going into the detail of preferred embodiments of the invention with reference to the drawings in particular, other optional features of the invention, which can be implemented in combination according to any combinations or alternatively, are indicated below:

the exposed portion 17 is located at the level of the peripheral edge 15 of the cover 12;

the exposed portion 17 is located at the level of the internal wall of a hole 14 formed in the cover 12;

the connection means comprise a flexible & printed electronics member 19 and/or a conductive layer 20, in contact simultaneously with

the exposed portion 17 and the given electrode 2, 7;

the flexible & printed electronics component 19 and/or the conductive layer 20 at least partially fills the hole 14;

the given electrode 2, 7 comprises an electrode layer 3 and a connection pad 5, 9, the connection pad 5, 9 being in contact with the flexible & printed electronics member 19 and/or the layer driver 20.

the contact recovery member 16 and the exposed portion 17 are offset laterally on the cover 12;

the cover 12 is of the flexible printed circuit board type;

the interconnection portion 18 is at least partly embedded in the thickness of the cover 12;

an electrical contact recovery member 16 and electrical connection means are included for each of the electrodes among the first electrode 2 and the second electrode 7.

The present invention also relates to a process for producing a flexible organic light-emitting diode as described previously, in which a flexible & printed electronics member 19 is deposited between the exposed portion 17 and the given electrode 2, 7 or a conductive layer 20 covering both at least part of the exposed portion 17 and of the given electrode 2, 7.

The following description shows an OLED on a support 1 but it is understood that a plurality of OLEDs can be formed in a similar manner. Support 1 is flexible. It is transparent or semi-transparent for light emission through this support 1; it is for example made of ultra-thin glass laminated on a plastic support for mechanical strength and better sealing.

On the , we see an OLED emitting light downwards. The OLED includes a lower electrode called the first electrode 2 located on the flexible support 1, a light-emitting organic structure, here called the organic layer 6, in which an electron-hole type conduction can develop, and an upper electrode, called the second electrode 7. Most often the electroluminescent organic layer 6 is itself laminated and may comprise a hole injection layer, a hole transport layer, a light emission layer produced by the recombination of holes and electrons , an electron transport layer and an electron injection layer. Generally, the anode and/or the cathode is composed of an oxide such as indium tin oxide (Indium Tin Oxide, ITO) or based on a thin layer of Ag. In this case, the anode is here the first electrode 2 and is advantageously semi-transparent at the very least.

For all of these layers, it is possible to use traditional formation methods in the field of microelectronics and in particular thermal evaporation techniques, of the physical or chemical type for example.

The first electrode 2 comprises an electrode layer 3 extending over a portion of the upper surface of the support 1. Advantageously, the layer 3 is not completely covered by the rest of the stack comprising the organic layer 6 and the second electrode 7. Thus, a zone 4 of the electrode layer 3 protrudes laterally so as to allow a connection of the layer 3 by the side of the stack of the OLED. This connection takes place in the example via a pad 5 which extends from the upper face of the electrode layer 3 parallel to the stack comprising the organic layer 6 and the second electrode 7. advantageously leaves a space between the stack comprising the organic layer 6 and the second electrode 7 and the pad 5.

The organic layer 6 is formed so that it is in contact with the upper face of the electrode layer 3 of the first electrode 2 in order to carry out electrical conduction between them. The other face of organic layer 6 is in contact with second electrode 7 over at least part of its surface. Like the first electrode 2, the second electrode 6 may comprise an electrode layer 7 extending above the organic layer 6 and a pad 9 supported by the support 1 in a manner parallel to the stack and in contact with the layer 7. In the case shown in , the pad 9 is in lateral contact with the electrode layer of the second 7.

It is not absolutely necessary for the pads 5 and 9 to reach the same height level above the support 1. Nevertheless, it is preferred that their respective height be at least at the height level of the upper face of the second electrode. 7 so as to facilitate the electrical connection of its pads 5 and 9 outside the OLED. The studs 5 and 9 can be thermally deposited and can for example be based on Al, Ag, copper or a copper alloy with titanium or chromium.

The assembly thus formed can be covered by an encapsulation layer 10. The latter is for example obtained by the technique of deposition of atomic layers (having the acronym ALD) which makes it possible to produce a protective layer, preferably formed in one material chosen from aluminum oxide (Al2O3), silicon dioxide (SiO2) or even titanium dioxide (TiO2), of excellent quality, with a thickness of between 10 and 100 nanometers typically. In general, the properties of layer 10 are configured to provide a protective seal for the underlying organic parts. Preferably, layer 10 completely overcomes second electrode 6 including pad 9 and joins support 1 laterally to pad 9 so as to isolate this part. At the same time, layer 10 advantageously extends in the space provided between the stack formed by layer 6 and layer 7 and pad 5, so as to laterally isolate organic layer 6 also on this side. The encapsulation layer 10 can join the upper face of the layer 3 of the first electrode 2. It will be noted that part of the first electrode 2 is not covered by the encapsulation layer 10; it will therefore be advantageous to use for these portions a material that is not very sensitive to oxidation or humidity; the previously mentioned ITO can do the trick. A masking step is preferably implemented, making it possible to spare the zones of the DELO on which the layer 10 is not to be formed.

According to the invention, a cover 12 is attached to the assembly thus formed so as to ensure an electrical connection of the electrodes 2, 7 from the outer face 13 of the cover 12.

The connection between the cover 12 and the upper surface of the previously described assembly can take place via an interface layer 11, for example in the form of an adhesive polymer material used for bonding the cover 12 by its inner side. In particular, the entire upper surface of the encapsulation layer 10 can be covered by the interface layer 11 while leaving the pad 5 accessible. Still advantageously, an opening is formed through the encapsulation layer 10 and interface layer 11 so as to allow access to pad 9. For pad 5, this opening is not necessary if pad 5 has been provided laterally relative to the stack of other layers.

Preferably, the cover 12 consists of a flexible printed circuit board of the PCB type (acronym for Printed Circuit Board). This card is based on a plastic material of an electrically insulating nature and comprises, on the surface and/or embedded inside the plastic material, electrically conductive tracks, advantageously made of copper, making it possible to establish electrical connections between different points. from the menu. The integration of conductive tracks inside the card can take place by a technology of stratification of this card, at least one of the strata located towards the inside of the card being able to bear conductive tracks on its surface.

In the case of the present invention, contact recovery members 16 are located at an outer face of the cover 12. These are, for example, OLED connection pads to the outside, for example made of copper or any other electrically conductive material. In the case of the invention, the contact recovery members 16 cooperate with electrical connection means so as to establish electrical continuity between these members 16 and the electrodes 2, 7 to which they are dedicated.

Thus, a similar system is advantageously produced for the electrical connection of the first electrode 2 and the electrical connection of the second electrode 7.

It is advantageous for the electrical connection means to comprise a portion 18 which extends laterally on the surface or inside the cover 12. This portion 18 may comprise a part oriented along the thickness of the cover 12 but above all comprises a part oriented transversely to this thickness so as to laterally offset the contact recovery member 16 in question and the electrical connection chain towards the corresponding electrode. Thus, for the contact recovery member 16 intended to connect the first electrode 2, the portion 18 extends, from the member 16 towards the right of the . At the distal end of the interconnection portion 18, an exposed portion 17 ensures the accessibility of the electrical connection means outside of the cover 12 and, according to the invention, at an edge of the cover 12. By edge is meant a portion of the surface accessible from the outside of the cover 12 directed along the thickness dimension of this cover. According to a first possibility, an edge part is formed by the peripheral edge of the cover 12. According to another possibility, an edge part is formed by at least a portion of the inner side wall of a hole formed inside the hood 12.

In the case of the , the peripheral edge 15 of the cover 12 is used as an exposed portion 17 for the connection of each of the electrodes 2, 7. The portion 18 therefore extends on or in the cover 12 between the contact recovery member 16 and said portion exposed 17. The latter is advantageously made of copper and is embedded or added to the level of the edge of the cover 12. The visualizes that the exposed portion 17 is laterally remote from the contact recovery member 16 of which it is in electrical continuity. It is understood that it is advantageous for the interconnection portion 18 to be embedded inside the insulating material of the cover 12 so as to protect these electrical lines.

The exposed portion 17 allows the connection of the corresponding electrode. To this end, it is advantageous for this electrode to include a pad 5, 9 as previously described so as to make the electrode in question accessible at a height level located close to the underside of the cover 12. In the case of the , apart from the thickness of the layers 10 and 11, the upper surface of the studs 5, 9 is immediately below the internal surface of the cover 12. Furthermore, the stud 5, 9 is preferably formed so that a part of its upper surface is in line with the corresponding exposed portion 17.

Preferably, the exposed portion 17 is accessible, not only by the edge of the cover 12, but also preferably by at least one of the outer 13 and inner faces of the cover 12.

Given the preferential thin thickness of the layers 10 and 11, it is not excluded to bring the exposed portion 15 into direct contact with the pad of the electrode in question. However, according to an advantageous embodiment of the invention, the electrical continuity at this level is achieved or at least reinforced by means of an electrical junction element. In the embodiment of the , this electrical junction element takes the form of a flexible & printed electronic device. It is for example possible to use a conductive paste based on silver or copper, or also a conductive polymer such as PEDOT:PSS doped with Ag nanoparticles. The flexible & printed electronics member 19 is in contact with the side flank exposed on the outside of the exposed portion 15 which is in contact with the corresponding electrode, advantageously via the corresponding pad. Preferably, the flexible & printed electronics member 19 is applied to the pad on the upper surface of the latter, in an orientation directed parallel to the plane of the cover, and on the exposed portion 15, in an orientation directed perpendicular to the cover plane and preferably parallel to the thickness of the latter. The flexible & printed electronics component 19 passes through the layers 10 and 11 if it is a question of connecting the second electrode 7. In the case of the use of flexible & printed electronics components 19, it It is advantageous for the material of the pads 5, 9 to be produced by metallic PVD deposition.

Advantageously, it is arranged so that the combination of the outer casing portions of the assembly thus constituted, comprising for example the outer face 13 of the cover 12, the side wall of the pad 5 and of the electrode layer 3 and the outer surface of the encapsulation layer 10 form a continuous assembly around the stack comprising the organic layer 6. Thus, the latter is effectively encapsulated.

There illustrates a slightly different embodiment from that of the . In this case, the flexible & printed electronics component 19 is replaced by a conductive layer 20 extending, like the component 19, at least so as to establish or reinforce the electrical continuity between the exposed portion 15 and the corresponding electrode, in particular its pad 5 or 9. The conductive layer 20 can be a layer of metallic material, for example deposited under vacuum (by thermal evaporation or even sputtering in particular) over a part of the external face 13 of the cover 12, at the level of the exposed portions 15. If it is desired to electrically connect the two electrodes by this technique, two electrically conductive layers 20 which are not electrically connected to each other will of course be formed. However, these two layers can be deposited simultaneously with a masking of intermediate parts.

As for the flexible & printed electronics member 19, the conductive layer 20 facilitates the connection sockets between the contact recovery members 16 and the pads 5, 9. As the deposition does not involve great precision (it is just necessary that the exposed portion 15 is covered just like the upper surface of the pad 5 or 9), the manufacture is facilitated. In addition, if the device comprises a plurality of DELOs made on the same support 1, this technique makes it possible to pool the phase of making the electrical junction of the exposed portions 15 and the pads 5, 9 within the same step. Indeed, the flexibility of the OLED is not affected by the low thickness of the conductive layer 20 less than 1 micron.

The conductive layer can be formed by or based on the following materials: copper, aluminum, silver, chromium, molybdenum, nickel, titanium. It will be noted that the conductive layer 20 can cover all or part of the side of the entire thickness of the diode so as to reinforce or form an encapsulation surface in certain places. The conductive layer 20 can therefore also act as a protective layer. Its material is advantageously airtight and waterproof.

For example, the shows that the side wall of the first electrode 2 is covered by the conductive layer 20 which corresponds thereto. This also improves the electrical connection of the assembly. It is possible in particular to use a thin conductive layer thickness, for example less than 1 μm, and preferably between 0.4 μm and 0.6 μm.

There shows an alternative to but still with the use of a flexible & printed electronics unit 19. the exposed portion 15 of the electrical connection means. It is therefore also at this location that the flexible & printed electronics unit 19 is present. At least part of the side wall of the hole 14 is exploited to produce the exposed portion 15. It is thus understood that one can freely define the lateral offset between the contact recovery member 16 and the location of the connection on the corresponding electrode, simply by defining the location of the hole 14 and whatever the size of the cover 12.

There is part of the same logic of the cover 12 having one or more holes 14 as the case of the . However, in this situation, as in the case of the , the junction element is made by means of a conductive layer 12. As before, the latter is deposited on the surface of the outer face 13 of the cover 12 so as to at least partially fill the hole 14 from above. and reach the upper face of the corresponding stud 5, 9.

It will be noted that in the situations of the embodiments of FIGS. 3 and 4, it

It is possible for the cover 12 to completely cover the two pads 5, 9 and therefore have exterior dimensions substantially equivalent to the exterior dimensions of the final diode.

The invention is not limited to the embodiments previously described, but extends to all embodiments in accordance with its spirit. The characteristics of the described and illustrated embodiments can be combined. For example, one or more holes can be used to connect one of the electrodes and the periphery of the cover can be used to connect the other electrode. Also, flexible & printed electronics can be implemented for one electrode and a conductive layer for the other. Finally, even if it is advantageous for the two electrodes to be connected according to one of the embodiments of the invention, it is possible to implement the invention for the connection of only one of the electrodes.

REFERENCES

1. Bracket

2. First electrode

3. Electrode layer

4. Area protruding

5. Plot

6. Organic Layer

7. Second electrode

8. Electrode layer

9. Plot

10. Encapsulation layer

11. Interface layer

12. Hood

13. Outer face

14. Hole

15. Edging

16. Body for resumption of contact

17. Exposed portion

18. Interconnection Portion

19. Organ of flexible & printed electronics

20. Conductive layer

Claims (12)

Organic light emitting diode comprising:
- A stack comprising an organic layer in contact by a first face with a first electrode (2), and in contact by a second face with a second electrode (7),
- The flexible support (1) based on an ultra-thin glass substrate laminated to a plastic support
- A first electrode (2), in contact with the flexible support
- A flexible cover (12) surmounting the second electrode (7) and comprising an outer face (13) carrying at least one electrical contact recovery member (16) electrically connected to a given electrode from among the first electrode (2) and the second electrode (7) by electrical connection means, characterized in that the electrical connection means comprise an exposed portion (17) along an edge of the cover (12) and an interconnection portion (18) extending transversely to a thickness dimension of the cover (12), between the contact recovery member 16 and the exposed portion (17). Diode according to the preceding claim, in which the exposed portion (17) is located at the level of the peripheral edge (15) of the cover (12). Diode according to Claim 1, in which the exposed portion (17) is located at the level of the internal wall of a hole (14) formed in the cover (12). Diode according to one of the preceding claims, in which the connection means comprise a flexible & printed electronics member (19) and/or a conductive layer (20) deposited by thermal evaporation, in contact simultaneously with the exposed portion ( 17) and the given electrode (2, 7). Diode according to the preceding claim and claim 3 in combination, in which the flexible & printed electronics member (19) and/or the conductive layer (20) at least partially fills the hole (14). Diode according to one of the two preceding claims, in which the given electrode (2, 7) comprises an electrode layer (3) and a bonding pad (5, 9), the bonding pad (5, 9) being in contact with the flexible & printed electronics component (19) and/or the conductive layer (20). Diode according to one of the preceding claims, in which the contact recovery member (16) and the exposed portion (17) are offset laterally on the cover (12). Diode according to one of the preceding claims, in which the cover (12) is of the flexible printed circuit board type. Diode according to one of the preceding claims, in which the interconnection portion (18) is at least partly embedded in the thickness of the cover (12). Diode according to one of the preceding claims, comprising an electrical contact recovery member (16) and electrical connection means for each of the electrodes among the first electrode (2) and the second electrode (7). Method for producing an organic light-emitting diode comprising:
-The formation of a stack on a flexible support (1), comprising successively and in order, the formation of a first electrode (2), the formation of an organic layer (6), the formation of a second electrode (7),
-The covering of the stack by surmounting the second electrode (7) with a flexible cover (12) comprising an outer face (13) carrying at least one electrical contact recovery member (16) electrically connected to a given electrode among the first electrode (2) and the second electrode (7) by electrical connection means characterized in that it comprises:
-The formation of an exposed portion (17) of the electrical connection means made along a slice of the cover and of an interconnection portion (18) extending, transversely to a thickness dimension of the cover (12), between the contact recovery member (16) and the exposed portion (17). Method according to the preceding claim, in which a flexible & printed electronic component (19) is deposited between the exposed portion (17) and the given electrode (2, 7) or a conductive layer (20) is deposited covering at the at least part of the exposed portion (17) and the given electrode (2, 7)