FR3101198A1 - Encapsulated Flexible Organic Light Emitting Diode - Google Patents

Abstract

The present invention relates to a flexible organic light-emitting diode 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 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 a section 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 supplied by an electric current, emit their own light. The present invention also relates to a method of making 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 convert electricity directly into light, while being d 'unparalleled efficiency in terms of energy consumption. Light-emitting diode lighting allows uniform distribution 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 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 wavelength band of the 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 size and aesthetics issues, this low thickness allows contexts of mechanical stress that are difficult to imagine on the basis of a light source of different technology. In particular, we are beginning to provide 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 the technical lighting (Automotive, Military, Medical, Aeronautics, etc.) with adapted 3D shapes.

If the organic layer allows such emission of light, it nevertheless exhibits poor resistance in contact with water or oxygen. Contact of the organic layer with water or oxygen produces oxidation and results in loss of chemical and electroluminescent properties. The lifespan of an OLED is thus directly linked to the quality of an encapsulation necessary to protect it from contact with water and oxygen. The maximum permissible water and oxygen penetration rate 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 produce a sealed encapsulation of an OLED, by protecting said OLED by a hollow cover made of thick glass bonded by an adhesive peripheral seal on a stack of layers comprising the organic layer, side opposite to the substrate. The volume between the hood and the DELO includes an inert gas. This thick glass hollow cover 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 produce a short cover leaving the electrical connectors accessible. Protective and encapsulating covers are often ultra-thin glass substrates less than 100 microns thick 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 deposition of the layers of the OLED. To overcome this problem, several substrates are used: mainly plastic. The plastic cover suffers from its poor sealing and its temperature resistance.

Taking into account the constraints associated with the manufacturing process for flexible light-emitting diodes, the present invention proposes to respond at least in part to the drawbacks of current techniques. In one aspect, the invention enables 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 with a first face of a first electrode, and in contact with a second face of 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 external face carrying at least one electrical contact pickup member electrically connected to a given electrode among the first electrode and the second electrode by electrical connection means,

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

The present invention also relates to a method of making 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 cover 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 section of the cover and of an interconnection portion extending, transversely to a dimension in thickness of the cover, between the contact recovery member and the portion exposed.

Thus, we can deport the place of contact recovery for the electrical connection of the flexible OLED to the outside, relative to a connection area on the electrode. This zone can be on the periphery of the OLED while the contact resuming member can 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 of accessing the electrodes of a flexible OLED is formed while providing an encapsulation effectively protecting the organic layer against contact with water and / or water. 'oxygen. In addition to having access to the electrodes, it is possible to have an electrical connection located in a specific area to facilitate addressing OLEDs if there are several.

BRIEF INTRODUCTION OF FIGURES

Other characteristics, aims and advantages of the present invention will become apparent on reading the following detailed description, with reference to the appended drawings, given by way of non-limiting example, and in which:

The illustrates an embodiment of the invention with contact resumption through the periphery of the cover and components of flexible & printed electronics;

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

The illustrates an embodiment of the invention with contact recovery through holes in the cover and components of flexible & printed electronics;

- The illustrates an embodiment of the invention with contact recovery through holes in the cover and conductive layer.

For clarity, items in the figures are not shown 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 each other but it means 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 include a plurality of layers. On the other hand, the term "layer" does not necessarily mean full plate distribution on the substrate.

Before entering 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 a combined manner in any combination 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 member of flexible & printed electronics 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 member of a flexible & printed electronics 19 and / or the conductive layer 20.

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

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

- The interconnection portion 18 is at least partially embedded in the thickness of the cover 12;

an electrical contact pickup 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 method of making a flexible organic light-emitting diode as described above, in which a flexible & printed electronic member 19 is deposited between the exposed portion 17 and the given electrode 2, 7 or is deposited a conductive layer 20 covering both at least a 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 to 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, an organic electroluminescent structure, here called organic layer 6, in which an electron-hole type conduction can develop, and an upper electrode, called the second electrode 7. Most often the organic electroluminescent layer 6 is itself laminated and may include a hole injection layer, a hole transport layer, a light emitting 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 at least semi-transparent.

For all of these layers, we can use traditional training 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 is made in the example by means of 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. It is 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 achieve electrical conduction between them. The other face of the organic layer 6 is in contact with the 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 that the pads 5 and 9 reach the same level of height above the support 1. However, it is preferred that their respective height is at least at the level of the height of the upper face of the second electrode. 7 so as to facilitate the electrical connection of its pads 5 and 9 to the outside of the OLED. The pads 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 with 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 an atomic layer. material chosen from aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ) or titanium dioxide (TiO ₂ ), of excellent quality, with a thickness 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, the layer 10 completely surmounts the second electrode 6 including the pad 9 and joins the support 1 laterally to the pad 9 so as to isolate this part. At the same time, the layer 10 advantageously extends in the space formed between the stack formed of the layer 6 and of the layer 7 and the pad 5, so as to laterally insulate the 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 which is not very sensitive to oxidation or to humidity; the aforementioned ITO may do the trick. A masking step is preferably implemented, making it possible to spare the areas of the OLED 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 assembly described above can take place by means of an interface layer 11, for example in the form of an adhesive polymer material used for bonding the cover 12 by its internal face. 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 of the interface layer 11 so as to allow access to the pad 9. For the pad 5, this opening is not necessary if the pad 5 has been provided laterally relative to the stack of other layers.

Preferably, the cover 12 is formed by 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 be achieved by a technology of laminating this card, at least one of the layers located towards the interior of the card being able to carry on its surface conductive tracks.

In the case of the present invention, contact recovery members 16 are located at an external face of the cover 12. These are for example connection pads from the OLED 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 that the electrical connection means 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 pick-up 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 to 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 the cover 12 and, according to the invention, at a section of the cover 12. The term “edge” is understood to mean 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, a wafer part is formed by the peripheral edge of the cover 12. According to another possibility, a wafer part is formed by at least a portion of the inner side wall of a hole formed inside the cover. cover 12.

In the case of , the peripheral edge 15 of the cover 12 is used as the 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 attached 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 will be 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 electric lines.

The exposed portion 17 allows the connection of the corresponding electrode. For this purpose, it is advantageous that this electrode comprises a pad 5, 9 as previously described so as to make the electrode considered accessible at a height level situated near 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 pads 5, 9 is immediately below the internal surface of the cover 12. Furthermore, the pad 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.

Taking into account 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 an organ of flexible & printed electronics. 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 component 19 is in contact with the side flank exposed to the outside of the exposed portion 15 which is in contact with the corresponding electrode, advantageously via the corresponding pad. Preferably, the member of a flexible & printed electronics 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 perpendicularly to the cover. plane of the cover and preferably parallel to the thickness of the latter. The part of a flexible & printed electronics 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 parts of a flexible & printed electronics 19, it It is advantageous for the material of the pads 5, 9 to be produced by metal deposition in PVD.

Advantageously, arrangements are made so that the combination of the outer casing portions of the assembly thus formed, comprising for example the outer face 13 of the cover 12, the side wall of the stud 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.

The illustrates a slightly different embodiment from that of the . In this case, the member of a flexible & printed electronics 19 is replaced by a conductive layer 20 extending, like the member 19, at least so as to establish or strengthen 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, of course two electrically conductive layers 20 which are not electrically connected to one another will be formed. However, these two layers can be deposited simultaneously with a masking of intermediate parts.

As for the component of a flexible & printed electronics 19, the conductive layer 20 facilitates the connection between the contact recovery members 16 and the pads 5, 9. As the deposition does not imply a great precision (it It is just necessary that the exposed portion 15 is covered just like the upper surface of the stud 5 or 9), the manufacture is facilitated. In addition, if the device comprises a plurality of OLEDs produced 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 of the pads 5, 9 within the same step. Indeed, the flexibility of the OLED is not affected because of the low thickness of the conductive layer 20 of less than 1 micron.

The conductive layer can be formed by or based on the following materials: copper, aluminum, silver, chromium, molybdenum, nickel, titanium. Note that the conductive layer 20 may cover all or part of the sidewall 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 watertight.

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

The shows an alternative to the but still with the use of a flexible & printed electronics member 19. This time, a hole 14 has been made so that it emerges through the thickness of the cover 12. It is at this level that is located. the exposed portion 15 of the electrical connection means. It is therefore also at this location that the flexible & printed electronics component 19 is present. At least part of the side wall of the hole 14 is used to produce the exposed portion 15. It is thus understood that it is possible with complete freedom to 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 hole 14 and regardless of the size of the cover 12.

The 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 produced by means of a conductive layer 12. As before, the latter is deposited on the surface of the external 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 pad 5, 9.

It will be noted that in the situations of the embodiments of FIGS. 3 and 4, it is possible that the cover 12 completely covers the two pads 5, 9 and therefore external dimensions substantially equivalent to the external dimensions of the final diode.

The invention is not limited to the embodiments previously described, but extends to all embodiments consistent with its spirit. The characteristics of the embodiments described and illustrated 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. Support
2. First electrode
3. Electrode layer
4. Protruding area
5. Plot
6. Organic layer
7. Second electrode
8. Electrode layer
9. Plot
10. Encapsulation layer
11. Interface layer
12. Hood
13. External face
14. Hole
15. Border
16. Contact recovery body
17. Exposed portion
18. Interconnection portion
19. Component of flexible & printed electronics
20. Conductive layer

Claims (12)

Organic light emitting diode 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) based on an ultra-thin glass substrate laminated on a plastic support
-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 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 the electrical connection means comprise an exposed portion (17) following a section 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). 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). A diode according to claim 1, wherein the exposed portion (17) is located at the inner 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 member of flexible & printed electronics (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). A diode according to the preceding claim and claim 3 in combination, wherein the flexible & printed electronics component (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 connection pad (5, 9), the connection pad (5, 9) being in contact with the organ of flexible & printed electronics (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 laterally offset 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 partially 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). A method of making 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 external 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 formed 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 member of flexible & printed electronics (19) is deposited between the exposed portion (17) and the given electrode (2, 5) or a conductive layer (20) covering the surface is deposited. times at least part of the exposed portion (17) and the given electrode (2, 5).