Light emitting module integrated with flexible organic light emitting diode

Abstract

The invention relates to a lighting module (1) of a lighting and / or signalling device of a motor vehicle, comprising: a flexible OLED (2) mounted on a transparent substrate (3) comprising an electrical interconnection layer; a support (4) of the flexible OLED, designed to shape the flexible OLED and at least a portion of the transparent substrate into a predetermined shape, the flexible OLED being fastened to the support by means of an adhesive (51); a flexible printed circuit board (6); characterized in that the transparent substrate comprises a portion (32) protruding beyond the OLED and facing a portion (43) of the support, the flexible printed circuit board being electrically connected to the interconnection layer at the portion of the transparent substrate, and the flexible printed circuit board being fastened to the portion of the support by means of an adhesive (52).

Description

[0001] The present invention relates to the field of automotive lighting and automotive signaling. More precisely, the present invention relates to the field of lighting and / or signaling devices comprising organic light emitting diodes.

[0002] In motor vehicles, organic light emitting diodes (OLEDs) are often used to perform or at least participate in performing one or more lighting and / or signaling functions. In particular, OLEDs offer many possibilities for shapes and styles, thus contributing to the aesthetics of the vehicle and the specific visual identity of the vehicle.

[0003] Conventionally, organic light emitting diodes are in the form of rigid surface light sources mounted on a support that allows the rigid surface light sources to be integrated into a light emitting and / or signaling device. Therefore, a flexible printed circuit board or flex is mechanically fastened to the support and electrically connected to the OLED so that it can be supplied with power and controlled. Therefore, the use of such a flexible printed circuit board provides a great degree of freedom for arranging the OLED in a light emitting and / or signaling device.

[0004] However, it is becoming increasingly common to use flexible organic light-emitting diodes, which offer greater freedom in styling and also make it possible to advantageously orient their emitting surfaces so as to be able to improve their visibility from outside the vehicle, whatever the viewing direction.

[0005] However, on the one hand, it is necessary to protect this type of flexible organic light-emitting diode, in particular from dust and moisture, and on the other hand, it is also necessary to shape this flexible organic light-emitting diode so that it assumes a desired shape. In this context, it is conventional to attach the flexible OLED to a glass substrate intended to protect the flexible OLED and to fasten the assembly to a rigid support capable of shaping the flexible OLED.

[0006] There is then the problem of mechanically fastening the flexible printed circuit board to the OLED. In particular, since the OLED is encapsulated between a glass substrate and a rigid support, it is necessary to mechanically fasten the flexible printed circuit board to the glass substrate, which is provided with an interconnection layer allowing electrical connection to the electrodes of the OLED. However, such fastening generates mechanical stresses on the glass substrate, which can then be affected by stresses and cracks. In this case, the cracks can allow moisture to penetrate into the OLED, so that the protective function of the glass substrate is no longer guaranteed. In addition, such cracks have an adverse effect on the aesthetic appearance of the OLED and can also damage the light beam emitted by the OLED.

[0007] There is therefore a need for a lighting module for a lighting and / or signaling device of a motor vehicle comprising flexible organic light-emitting diodes and overcoming the mentioned disadvantages, in particular integrating a flexible printed circuit board mechanically fastened to the module without risking weakening the protective substrate of the diodes.

[0008] The present invention falls within this background and is intended to meet this need.

[0009] For these purposes, a subject of the invention is a lighting module for a lighting and / or signaling device of a motor vehicle, comprising:

[0010] a. A flexible organic light emitting diode mounted on a transparent substrate, the transparent substrate comprising an interconnect layer comprising an electrical trace network for supplying power to the organic light emitting diode;

[0011] b. a support for the flexible organic light-emitting diode, the support being designed to shape the flexible organic light-emitting diode and at least a portion of the transparent substrate into a predetermined shape; the at least a portion of the organic light-emitting diode being fastened to the support by means of an adhesive;

[0012] c. Flexible printed circuit board.

[0013] The light emitting module is characterized in that the transparent substrate includes a portion protruding beyond the organic light emitting diode and facing a portion of the support, the flexible printed circuit board is electrically connected to the interconnection layer at the portion of the transparent substrate, and the flexible printed circuit board is fastened to the portion of the support by means of an adhesive.

[0014] It will therefore be appreciated that the protective substrate of the OLED extends beyond the OLED to define a portion dedicated to the electrical connection between the flexible printed circuit board and the OLED. However, this portion does not substantially play a role in mechanically retaining the printed circuit board. Therefore, an adhesive layer is provided between the flexible printed circuit board and the support of the OLED, the adhesive layer also extending beyond the OLED, so that the flexible printed circuit board is mechanically retained on the support rather than on the protective substrate. Thus, mechanical stresses that are liable to affect the protective substrate due to the flexible printed circuit board are substantially eliminated, and the risk of cracking of the protective substrate is therefore minimized.

[0015] In the present invention, the term “flexible organic light emitting diode” is understood to mean an organic light emitting diode that can be deformed without breaking, in particular by folding it or bending it, and without substantially changing its light emitting function.

[0016] For example, a flexible OLED may include multiple layers, including an organic layer surrounded by a cathode and an anode. The organic layer may include individual layers made of different organic materials. For example, the organic layer may include a light-emitting layer, a layer that promotes electron transfer to the emission layer, a layer that promotes hole transfer to the emission layer, a layer that blocks holes from the upper layer, and a layer that blocks electrons from the lower layer. Therefore, all of these layers constitute a microcavity, the thickness of which is adjusted to produce optical resonance. Therefore, a selective interference reflector constituting a resonant cavity is produced.

[0017] Therefore, when the current transmitted by the anode passes through the organic layer, the upper emission surface of the emission layer emits light radiation, which propagates through the upper layer transparent to the radiation, and the lower emission surface of the emission layer emits light radiation, which propagates through the lower layer transparent to the radiation. For example, one of the cathode and the anode can be arranged to be made of a reflective material, or a reflective coating can be applied to one of the cathode and the anode so as to reflect the light radiation toward the other of the cathode and the anode, the other of which is made of a transparent conductive material (such as transparent indium tin oxide (ITO)) so as to form a single light-emitting surface of the OLED. Therefore, a transparent substrate is attached to the light-emitting surface. An optical transmission layer can be arranged between the transparent electrode and the transparent substrate.

[0018] If desired, the OLED may comprise a thermal interface layer via which the OLED is fastened to the support, the adhesive then being arranged between this layer and the support.

[0019] As an indication, the thickness of the OLED (i.e. the thickness of the electrodes, the organic layer and the thermal interface layer) may be less than 1 mm, in particular substantially equal to 200 μm, while the area of ​​the light emitting surface may be greater than 1 cm 2 , or greater than 10cm 2 If desired, the thickness of the transparent substrate may be substantially less than 1 mm, in particular substantially equal to 100 μm.

[0020] In the present invention, the transparent substrate may advantageously be made partly or completely of glass. In a variant, the transparent substrate may be made of a transparent plastic polymer.

[0021] Advantageously, the support may be designed to shape at least a portion or all of the organic light emitting diode and the transparent substrate along a three-dimensional surface. The term "three-dimensional surface" is understood to mean a surface that is curved in at least one given direction, that is, no matter what reference system is chosen, three Cartesian coordinates are required to define each point of the surface. Advantageously, the predetermined shape is a regular surface.

[0022] Preferably, the support comprises means for fastening the lighting module to the lighting and / or signalling device.For example, the support may comprise fastening brackets which are intended to be screwed or snap-fastened to the housing of the lighting and / or signalling device.

[0023] In the present invention, the expression "flexible printed circuit board" (also referred to as the expression "flexible printed circuit" or the term "flexible board") denotes an assembly consisting of a particularly flexible and planar electrically insulating support (also referred to as a flexible insulating support) and particularly flat metal conductors intended to ensure the transmission of electrical signals to the flexible organic light-emitting diode, in particular the transmission of electrical power for supplying power to the flexible organic light-emitting diode and / or control signals for controlling all or part of the lighting of the flexible organic light-emitting diode.

[0024] Advantageously, the adhesive fastening the flexible printed circuit board to the support is the same adhesive fastening the organic light-emitting diode to the support.

[0025] For example, the adhesive may be a double-sided adhesive layer, such as a film or tape. For example, the layer may include an acrylic foam core coated with adhesive coatings on both sides, which may be the same or different. The foam core makes it possible to absorb mechanical stresses without compromising the fastening function of the adhesive layer.

[0026] Preferably, the double-sided adhesive layer fastening the flexible printed circuit board to the support and the double-sided adhesive layer fastening the organic light-emitting diode to the support come from the same double-sided adhesive tape. It will therefore be understood that in this case the thickness of these layers will be the same. This feature makes it possible to particularly facilitate the manufacture of the light-emitting module and avoid mechanical stresses on the transparent substrate, which could occur if the adhesive layers at the OLED and the flexible printed circuit board had different thicknesses.

[0027] Advantageously, the organic light emitting diode comprises a first light emitting face, the transparent substrate covering the light emitting face. If necessary, the organic light emitting diode is mounted on a support via a second face opposite to the first face of the organic light emitting diode, and the interconnection layer of the transparent substrate extends on a face of the transparent substrate located on one side of the organic light emitting diode.

[0028] Advantageously, the network of electrical traces of the interconnect layer is laid on the face of the transparent substrate on the side of the organic light emitting diode. For example, before assembly, a layer of conductive transparent material (such as indium tin oxide or ITO) can be deposited on the face of the transparent substrate and then mechanically, optically or chemically modified to form the network.

[0029] Preferably, the flexible printed circuit board is electrically connected to the interconnect layer by means of an anisotropic conductive adhesive connector arranged between an edge of the flexible printed circuit board and the portion of the transparent substrate. Thus, the connector may be provided as an anisotropic conductive film (ACF) or an anisotropic conductive paste (ACP).

[0030] In one embodiment of the present invention, the flexible organic light emitting diode is mounted on a first region of the transparent substrate, and the flexible printed circuit board is electrically connected to the interconnect layer in a second region of the portion of the transparent substrate. If necessary, the first region and the second region are separated by a third region of the portion of the transparent substrate, and the light emitting module has no adhesive between the support and the transparent substrate in the third region.

[0031] In particular, it has been found that some adhesives may include corrosive components, such as chlorinated compounds. In this case, the adhesive used to fasten the flexible OLED and the flexible printed circuit board may directly contact the transparent substrate in the third region, which potentially causes corrosion and cracks in the substrate. Therefore, removing the adhesive in the third region makes it possible to prevent such corrosion.

[0032] Advantageously, it may be provided that a single layer of double-sided adhesive is deposited over the entire support, then the portion of the layer corresponding to the third area is removed, and then the flexible organic light-emitting diode and the flexible printed circuit board are bonded to the remaining layer.

[0033] Advantageously, said portion of the support forms a step relative to the rest of the support. This thus ensures that, in the case where the thickness of the OLED differs from the thickness of the printed circuit board and possible connectors, while the thickness of the adhesive is constant, the thickness difference relative to the transparent substrate is compensated, thereby avoiding mechanical stresses on this substrate.

[0034] The subject matter of the invention is also a lighting and / or signaling device for a motor vehicle, which lighting and / or signaling device comprises a lighting module according to the invention.

[0035] The present invention will now be described using examples, which are for illustration purposes only and in no way limit the scope of the invention, and with reference to the accompanying drawings, in which the various figures show:

[0036] [ Figure 1 ] schematically and partially shows a front view of a light emitting module according to an embodiment of the present invention;

[0037] [ Figure 2 ] schematically and partially shows [ Figure 1 ] an exploded view of a light emitting module;

[0038] [ Figure 3 ] schematically and partially shows [ Figure 1 ] is a cross-sectional view of a light emitting module.

[0039] In the following description, elements that are identical in structure or function and appear in the various figures retain the same reference numerals unless otherwise specified.

[0040] [ Figure 1 ] shows a front view of a lighting module 1 of a lighting and / or signaling device for a motor vehicle according to one embodiment of the present invention. [ Figure 2 ] shows an exploded view of the light emitting module 1, and [ Figure 3 ] shows a cross-sectional view of the light emitting module 1 through the plane P.

[0041] The light emitting module 1 comprises a flexible organic light emitting diode or OLED 2 mounted on a glass substrate 3 .

[0042] More specifically, the OLED 2 is a bottom emission OLED. The OLED comprises an organic layer 21 surrounded by a cathode 22 made of a reflective material and an anode 23 made of transparent indium tin oxide. A thermal interface layer 24 is bonded to the cathode 22.

[0043] The glass substrate 3 is attached to the anode 23. The glass substrate comprises an interconnect layer (not shown) comprising a network of electrical traces for supplying power to the OLED 2, which is laid on the face 31 of the substrate 3 bonded to the OLED 2 and electrically connected to the anode 23.

[0044] When the current transmitted by the substrate 3 and the anode 23 passes through the organic layer 21 , the emitting layer emits light radiation, which propagates through the other layers until it reaches the anode 23 or reaches the cathode 22 through which it passes and which reflects the light radiation in the direction of the anode 23 .

[0045] Thus, the anode 23 and the extended portion of the glass substrate 3 form the emission surface of the OLED 2 .

[0046] In the example described, the thickness of the OLED 2 is substantially equal to 200 μm and the thickness of the transparent substrate is substantially equal to 100 μm, while the area of ​​the emitting face may be greater than 1 cm 2 , or even larger than 10cm 2 Therefore, the OLED 2 and the glass substrate 3 can be deformed to be folded, bent, or twisted without changing the light-emitting function of the OLED 2.

[0047] To shape the OLED 2 and the glass substrate 3 , the lighting module 1 comprises a support 4 having a receiving surface 41 for receiving the OLED 2 , the receiving surface having a three-dimensional shape, in particular of the regular surface type, and defined according to the shape desired to be given to the OLED 2 .

[0048] The OLED 2 is thus fastened to this receiving surface 41 of the support 4 by means of a double-sided adhesive layer 51 which is cut to the shape of the OLED 2. When mounting the light-emitting module, the double-sided adhesive tape is thus attached to the receiving surface 41 and then cut to form the layer 51. The back face of the OLED, defined by the face of the thermal interface layer 24 and opposite to the emission face defined by the anode 23, is then attached to the layer 51 in order to fasten the OLED 2 to the support and to shape the OLED.

[0049] It should be noted that the support 4 may also play a role in integrating the lighting module 1 into a lighting and / or signaling device, in addition to the function of shaping the OLED 2. For this purpose, it may be provided, for example, that a fastening member (not shown) is added to the support 4 at its surface 42 opposite to the receiving surface 41, such as a bracket intended to be screwed or snap-fastened to the housing of the lighting and / or signaling device.

[0050] To supply power to the network of electrical tracks etched in the face 31, the lighting module 1 comprises a flexible printed circuit board 6. This board 6 comprises, at one of the ends, a connector 61 intended to be connected directly or indirectly to means for controlling the supply of power to the OLED 2, provided in the lighting and / or signalling device.

[0051] The glass substrate 3 comprises a portion 32 extending beyond the emitting face of the OLED 2. In order to electrically connect the board 6 to the network of electrical traces, an anisotropic conductive film or ACF 62 is provided at the end of the board 6 opposite to the end supporting the connector 61. This ACF connector 62 is thus attached to the portion 32 so as to make electrical contact with a section of the network of electrical traces etched on this portion 32.

[0052] However, it is necessary to prevent the plate 6 from being mechanically fastened to the glass substrate 3 in order not to generate mechanical stresses on the substrate 3. For these purposes, the support 4 comprises a portion 43 facing the portion 32 of the substrate 3.

[0053] The flexible printed circuit board 6 is thus mechanically fastened to the portion 43 of the support 4 by means of the double-sided adhesive layer 52 .

[0054] In the example described, the layers 51 and 52 come from the same double-sided adhesive tape, which simplifies the manufacturing process of the module 1. On the other hand, in this context, these layers 51 and 52 have the same thickness, in particular a thickness of substantially 1.1 mm. However, there is a significant difference in thickness between the OLED 2 and the plate 6, which creates a height difference between the OLED 2 and the plate 6 relative to the substrate 3. In order to compensate for this thickness difference, the portion 43 of the substrate forms a step relative to the substrate. Thus, the generation of mechanical stresses on the substrate 3 is further avoided.

[0055] It should also be noted that the area 33 of the substrate 3 supporting the OLED 2 and the area 34 of the portion 32 to which the board 6 is connected via the ACF connector 62 are separated from each other by an area 35 of this portion 32. In order to prevent the corrosive components of the double-sided adhesive layer from damaging the glass substrate 3, the portion 53 of the double-sided adhesive strip located in this area 35 is removed during cutting of the strip.

[0056] It should be noted that the lighting module 1 can thus participate in performing a given photometric function, such as a direction indicator, a position light or a reversing light. The lighting module 1 can be used alone or in combination with other identical lighting modules 1 .

[0057] The above description clearly explains how the invention makes it possible to achieve its objectives, namely to provide a lighting module comprising a flexible organic light-emitting diode and a flexible printed circuit board mechanically fastened to the module without risking weakening the protective substrate of the diode. These objectives are achieved in particular by separating the electrical connection function and the mechanical fastening function and adding a portion for the electrical connection to the protective substrate and a portion for the mechanical fastening to the support of the diode.

[0058] In any case, the invention is not limited to the embodiments specifically described in this document and extends in particular to all equivalent devices and to any technically operable combination of these devices. In particular, a protective substrate made of a material other than glass, in particular a transparent plastic polymer, can be provided. It can also be provided that the flexible printed circuit board is electrically connected to the organic light-emitting diode or the transparent substrate by means of another type of connector.

Claims

1. A lighting module (1) for a lighting and / or signaling device of a motor vehicle, the lighting module comprising: a. A flexible organic light emitting diode (2) mounted on a transparent substrate (3), the transparent substrate comprising an interconnect layer, the interconnect layer comprising a network of electrical traces for supplying power to the organic light emitting diode; b. a support (4) for the flexible organic light-emitting diode, the support being designed to shape the flexible organic light-emitting diode and at least a portion of the transparent substrate into a predetermined shape; the at least a portion of the organic light-emitting diode being fastened to the support by means of an adhesive (51); c. Flexible printed circuit board (6); The invention is characterized in that the transparent substrate comprises a portion (32) protruding beyond the organic light emitting diode and the portion (32) faces a portion (43) of the support member, the flexible printed circuit board is electrically connected to the interconnection layer at the portion of the transparent substrate, and the flexible printed circuit board is fastened to the portion of the support member by means of an adhesive (52).

2. The lighting module (1) according to the preceding claim, wherein: The adhesive (52) that fastens the flexible printed circuit board (6) to the support (4) is the same as the adhesive (51) that fastens the organic light emitting diode (2) to the support.

3. The lighting module (1) according to the preceding claim, wherein: The adhesive (51, 52) is a double-sided adhesive layer.

4. The lighting module (1) according to the preceding claim, wherein: The double-sided adhesive layer (52) that fastens the flexible printed circuit board (6) to the support (4) and the double-sided adhesive layer (51) that fastens the organic light-emitting diode to the support (4) are from the same double-sided adhesive tape.

5. The lighting module (1) according to one of the preceding claims, characterized in that The organic light emitting diode (2) comprises a first light emitting surface (23), the transparent substrate (3) covers the light emitting surface, the organic light emitting diode is mounted on the support (4) via a second surface (24) opposite to the first surface of the organic light emitting diode, and the interconnection layer of the transparent substrate extends on a surface (31) of the transparent substrate located on one side of the organic light emitting diode.

6. The lighting module (1) according to one of the preceding claims, wherein: The electrical trace network of the interconnect layer is laid on the face (31) of the transparent substrate on the side of the organic light emitting diode.

7. The lighting module (1) according to one of the preceding claims, wherein: The flexible printed circuit board (6) is electrically connected to the interconnect layer by means of an anisotropic conductive adhesive connector (62) arranged between an edge of the flexible printed circuit board and the portion (32) of the transparent substrate.

8. The lighting module (1) according to one of the preceding claims, characterized in that The flexible organic light emitting diode (6) is mounted on a first area (33) of the transparent substrate (3), the flexible printed circuit board (6) is electrically connected to the interconnection layer in a second area (34) of the portion (33) of the transparent substrate, and the first area and the second area are separated by a third area (35) of the portion of the transparent substrate, and the light emitting module has no adhesive between the support (4) and the transparent substrate in the third area.

9. The lighting module (1) according to one of the preceding claims, characterized in that The portion (43) of the support (4) forms a step relative to the rest of the support.

10. A lighting and / or signaling device for a motor vehicle, comprising a lighting module (1) as claimed in one of the preceding claims.

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