Light module incorporating a flexible organic light-emitting diode

Abstract

The invention relates to a light module (1) for a motor vehicle lighting and / or signaling device, comprising a flexible OLED (2) mounted on a transparent substrate (3) having an electrical interconnect layer; a flexible OLED support (4) arranged to conform at least a portion of the flexible OLED and the transparent substrate into a predetermined shape, the flexible OLED being attached to the support by means of an adhesive (51); a flexible printed circuit board (6); characterized in that the transparent substrate has a portion (32) extending from the OLED and facing a portion (43) of the support, in that the flexible printed circuit board is electrically connected to the interconnect layer at this portion of the transparent substrate, and in that the flexible printed circuit board is attached to this portion of the support by means of an adhesive (52). Figure to be published with the abstract: Fig. 1

Description

Title of the invention: Light module integrating a flexible organic light-emitting diode

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

[0002] In motor vehicles, it is common to use organic light-emitting diodes (OLEDs) in order to perform, or at least participate in performing, one or more lighting and / or signaling functions. Indeed, OLEDs offer numerous possibilities in terms of shapes and styles, thus contributing to the aesthetics of the vehicle as well as its specific visual signature.

[0003] Conventionally, an organic light-emitting diode is in the form of a rigid surface light source, which is mounted on a support allowing its integration into a lighting and / or signaling device. A flexible printed circuit board, or "flexboard", is thus mechanically fixed to the support and electrically connected to the OLED in order to be able to power and control it. The use of this flexible printed circuit board thus offers great freedom of arrangement of the OLED in the lighting and / or signaling device.

[0004] However, it is becoming common to use flexible organic light-emitting diodes, which offer increased freedom of style and also allow their emitting surfaces to be advantageously oriented so as to be able to improve their visibility from outside the vehicle, whatever the direction of observation.

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

[0006] There is then a problem in the mechanical attachment of the flexible printed circuit board to the OLED. Indeed, since the OLED is encapsulated between the glass substrate and the rigid support, it is necessary to mechanically attach the flexible printed circuit board to the glass substrate, the latter being provided with an interconnection layer allowing an electrical connection with the electrodes of the OLED. However, this attachment creates a mechanical stress on the glass substrate which can then undergo stress and crack. In this case, the crack can allow moisture to infiltrate towards the OLED, so that the protective function of the glass substrate is no longer ensured. Furthermore, this crack harms the aesthetic appearance of the OLED and can also degrade the light beam emitted by the OLED.

[0007] There is thus a need for a light module of a lighting and / or signaling device for a motor vehicle incorporating a flexible organic light-emitting diode and overcoming the aforementioned drawbacks, and in particular which incorporates a flexible printed circuit board mechanically fixed to the module without risking weakening the protective substrate of the diode.

[0008] The present invention is placed in this context, and aims to meet this need.

[0009] For these purposes, the invention relates to a light module of a lighting device and / or motor vehicle signaling, comprising: a. a flexible organic light-emitting diode mounted on a transparent substrate, said transparent substrate comprising an interconnection layer comprising a network of electrical tracks intended for the electrical supply of the organic light-emitting diode; b. a support for said flexible organic light-emitting diode, the support being arranged to conform at least a portion of the flexible organic light-emitting diode and the transparent substrate to a predetermined shape; said at least a portion of the organic light-emitting diode being fixed to the support by means of an adhesive; c. a flexible printed circuit board.

[0010] The light module is characterized in that the transparent substrate comprises a portion protruding from the organic light-emitting diode and facing a portion of the support, in that the flexible printed circuit board is electrically connected to the interconnection layer at this portion of the transparent substrate and in that the flexible printed circuit board is fixed to this portion of the support by means of an adhesive.

[0011] It is thus understood 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 plays substantially no role in the mechanical maintenance of this printed circuit board. A layer of adhesive is thus provided between the flexible printed circuit board and the support of the OLED, which also extends beyond the OLED, so that the flexible printed circuit board is mechanically maintained on this support, and not on the protective substrate. Consequently, the mechanical stress that this protective substrate is likely to undergo, due to the flexible printed circuit board, is substantially eliminated, and the risk of cracking of this protective substrate is thus minimized.

[0012] In the invention, the term “flexible organic light-emitting diode” means an organic light-emitting diode that can be deformed without breaking, in particular by bending or curving it, and without significantly altering its light-emitting function.

[0013] For example, the flexible OLED may comprise several layers, including an organic layer framed by a cathode and an anode. The organic layer may comprise different strata made from different organic materials. For example, the organic layer may comprise a light-emitting stratum, a stratum promoting the transport of electrons to the emitting stratum and a stratum promoting the transport of holes to the emitting stratum, a stratum blocking holes coming from the upper layers and a stratum blocking electrons coming from the lower strata. All of these strata thus constitute a microcavity whose thickness is adjusted to create an optical resonance. Thus, selective interference reflectors are produced which constitute resonant cavities.

[0014] Thus, when the organic layer is traversed by an electric current transmitted by the anode, an upper emitting surface of the emitting layer emits light radiation propagating through the upper layers which are transparent relative to this radiation and a lower emitting surface of the emitting layer emits light radiation propagating through the lower layers which are transparent relative to this radiation. For example, it may be provided that one of the cathode and the anode is made of a reflective material or even to add a reflective coating on one of the cathode and the anode to reflect the light radiation towards the other of the cathode and the anode, which is made of a transparent conductive material, such as transparent indium-tin oxide (ITO), in order to form a single light-emitting face of the OLED.The transparent substrate is thus attached to this light-emitting face. An optical transfer layer can be provided between the transparent electrode and the transparent substrate.

[0015] If desired, the OLED may include a thermal interface layer, via which the OLED is fixed to the support, the adhesive thus being arranged between this layer and the support.

[0016] For information purposes, the thickness of the OLED, i.e. 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 face may be greater than 1 cm2, or even greater than 10 cm2. Where appropriate, the thickness of the transparent substrate may be substantially less than 1 mm, in particular substantially equal to 100 μm.

[0017] In the invention, the transparent substrate may advantageously be made, partially or totally, of glass. Alternatively, the transparent substrate may be made of a transparent plastic polymer.

[0018] Advantageously, the support can be arranged to conform at least a portion, or even all of the organic light-emitting diode and the transparent substrate to a three-dimensional surface. The term "three-dimensional surface" means a surface curved in at least one given direction, i.e. three Cartesian coordinates are necessary to define each of the points of the surface, regardless of the chosen reference frame. Advantageously, the predetermined shape is a ruled surface.

[0019] Preferably, the support comprises members for fixing the light module to the lighting and / or signaling device. For example, the support may comprise fixing lugs intended to be screwed or snapped onto a housing of the lighting and / or signaling device.

[0020] In the invention, the expression "flexible printed circuit board", also referred to as a flexible printed circuit, or the English term "flexboard", denotes an assembly consisting of an electrically insulating support, in particular flexible and flat - also referred to as a flexible insulating support - and metal conductors, in particular flat, intended to ensure transmission of electrical signals to the flexible organic light-emitting diode, and in particular transmission of electrical power intended for the electrical supply of the flexible organic light-emitting diode and / or control signals intended to control the lighting of all or part of the flexible organic light-emitting diode.

[0021] Advantageously, the adhesive fixing the flexible printed circuit board to the support is identical to the adhesive fixing the organic light-emitting diode to the support.

[0022] For example, the adhesive may be a layer of double-sided adhesive, such as a film or tape. For example, said layer may comprise an acrylic foam core coated on each side with an adhesive coating, these coatings being able to be identical or not. The foam core makes it possible to absorb mechanical stresses without the fixing function of the adhesive layer being degraded.

[0023] Preferably, the layer of double-sided adhesive fixing the flexible printed circuit board to the support and the layer of double-sided adhesive fixing the organic light-emitting diode to the support are made from the same double-sided adhesive tape. It is thus understood that the thicknesses of these layers will be identical in this case. This characteristic makes it possible in particular to facilitate the manufacture of the light module, and to avoid placing mechanical stresses on the transparent substrate, which could be the case if the layers of adhesive at the level of the OLED and the flexible printed circuit board have different thicknesses.

[0024] Advantageously, the organic light-emitting diode comprises a first light-emitting face, the transparent substrate covering this light-emitting face. Where appropriate, the organic light-emitting diode is mounted on the support via a second face opposite its first face, and the interconnection layer of the transparent substrate extends over the face of the transparent substrate located on the side of the organic light-emitting diode.

[0025] Advantageously, the network of electrical tracks of the interconnection layer is deposited on said face of the transparent substrate located on the side of the organic light-emitting diode. For example, a layer of transparent electrically conductive material, such as indium-tin oxide or ITO, can be deposited on said face of the transparent substrate, before assembly, and then be modified, mechanically, optically or chemically, to form said network.

[0026] Preferably, said flexible printed circuit board is electrically connected to the interconnection layer by means of an anisotropic conductive adhesive type connector arranged between an edge of said flexible printed circuit board and said portion of the transparent substrate. It may thus be provided that the connector is an anisotropic conductive adhesive film, or ACF (from the English "Anisotropic Conductive Film") or an anisotropic conductive adhesive paste, or ACP (from the English "Anisotropic Conductive Paste").

[0027] In one embodiment of the invention, the flexible organic light-emitting diode is mounted on a first area of ​​the transparent substrate, and the flexible printed circuit board is electrically connected to the interconnection layer at a second area of ​​the portion of the transparent substrate. Where appropriate, the first area and the second area are separated by a third area of ​​the portion of the transparent substrate, the light module being devoid of adhesive between the support and the transparent substrate at the third area.

[0028] It has indeed been found that certain adhesives may include corrosive components, such as chlorinated compounds. In this case, the adhesive used to fix the flexible OLED and the flexible printed circuit board may be in direct contact with the transparent substrate at this third zone, which may cause corrosion of this substrate and the appearance of cracks. The elimination of the adhesive at this third zone thus makes it possible to avoid this corrosion.

[0029] Advantageously, it will be possible to deposit a single layer of double-sided adhesive over the entire support, then to remove a part of this layer corresponding to the third zone, before then gluing the flexible organic light-emitting diode and the flexible printed circuit board onto the remaining layer.

[0030] Advantageously, said portion of the support forms a step with respect to the rest of the support. In the case where the thickness of the OLED is different from the thickness of the printed circuit board, and possibly of the connector, while the thickness of the adhesive is constant, this ensures that this difference in thickness with respect to the transparent substrate is compensated, so as to avoid creating mechanical stresses on this substrate.

[0031] The invention also relates to a lighting and / or signaling device for a motor vehicle comprising a light module according to the invention.

[0032] The present invention is now described with the aid of examples which are purely illustrative and in no way limitative of the scope of the invention, and from the appended drawings, drawings in which the various figures represent:

[0033] [Fig-1] represents, schematically and partially, a front view of a module luminous according to one embodiment of the invention;

[0034] [Fig.2] represents, schematically and partially, an exploded view of the light module of [Fig.l];

[0035] [Fig.3] represents, schematically and partially, a sectional view of the light module of [Fig.l].

[0036] In the following description, elements that are identical, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.

[0037] [Fig.l] shows a front view of a light module 1 of a lighting and / or signaling device of a motor vehicle, according to one embodiment of the invention. [Fig.2] shows an exploded view of the light module 1, while [Fig.3] shows a sectional view of the light module 1 through a plane P.

[0038] The light module 1 comprises a flexible organic light-emitting diode or OLED 2 mounted on a glass substrate 3.

[0039] More precisely, OLED 2 is a bottom emission type OLED. It comprises an organic layer 21 framed 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.

[0040] The glass substrate 3 is attached to the anode 23. It comprises an interconnection layer (not shown) comprising a network of electrical tracks intended for the electrical supply of the OLED 2, this network being deposited on the face 31 of the substrate 3 joining the OLED 2, and electrically connected to the anode 23.

[0041] When the organic layer 21 is traversed by an electric current transmitted by the substrate 3 and the anode 23, the emitting layer emits light radiation propagating through the other layers until it either reaches the anode 23, which it passes through, or until it reaches the cathode 22, which reflects it in the direction of the anode 23.

[0042] The anode 23, and by extension a part of the glass substrate 3, thus forms an emission face of the OLED 2.

[0043] 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 light-emitting face may be larger than 1 cm2, or even larger than 10 cm2. It is thus possible to deform the OLED 2 and the glass substrate 3 to bend, curve or twist them, without the light-emitting function of the OLED 2 being impaired.

[0044] In order to conform the OLED 2 and the glass substrate 3, the light module 1 comprises a support 4, which has a receiving surface 41 of the OLED 2 of three-dimensional shape, in particular of the ruled surface type, and defined according to the shape that one wishes to give to the OLED 2.

[0045] The OLED 2 is thus fixed to this receiving surface 41 of the support 4 by means of a layer of double-sided adhesive 51, cut to the shape of the OLED 2. When mounting the light module, a double-sided adhesive tape is thus affixed to the receiving surface 41, then cut to form the layer 51. Then the rear face of the OLED, defined by the face of the thermal interface layer 24 and opposite the emission face defined by the anode 23, is affixed to the layer 51 to fix the OLED 2 to the support and conform it.

[0046] It should be noted that in addition to its function of conforming the OLED 2, the support 4 can also play a role in the integration of the light module 1 into the lighting and / or signaling device. For this purpose, provision may be made to add to the support 4, for example at a surface 42 of the support 4 opposite the receiving surface 41, fixing members (not shown), such as tabs intended to be screwed or snapped onto a housing of the lighting and / or signaling device.

[0047] In order to provide electrical power to the network of electrical tracks etched in the face 31, the light module 1 comprises a flexible printed circuit board 6. This board 6 comprises at one of its ends a connector 61 intended to be connected, directly or indirectly, to a device for controlling the electrical power supply of the OLED 2, provided in the lighting and / or signaling device.

[0048] The glass substrate 3 comprises a portion 32, extending beyond the emission face of the OLED 2. In order to electrically connect the card 6 to the network of electrical tracks, an anisotropic conductive adhesive film, or ACF, 62 is provided at the end of the card 6 opposite the end supporting the connector 61. This ACF connector 62 is thus attached to the portion 32 to electrically connect to a section of the network of electrical tracks etched on this portion 32.

[0049] It is however necessary to avoid the card 6 being mechanically fixed to the glass substrate 3, so as not to generate stress or mechanical strain on the substrate 3. For these purposes, the support 4 comprises a portion 43, facing the portion 32 of the substrate 3.

[0050] The flexible printed circuit board 6 is thus mechanically fixed to this portion 43 of the support 4 by means of a layer of double-sided adhesive 52.

[0051] In the example described, the layers 51 and 52 come from the same double-sided adhesive tape, so that the manufacturing process of the module 1 is simplified. On the other hand, in this context, these layers 51 and 62 have an identical thickness, in particular of substantially 1.1 mm. However, there is a significant difference in thickness between the OLED 2 and the card 6, which generates a difference in height between the OLED 2 and the card 6 with respect to the substrate 3. In order to compensate for this difference in thickness, the portion 43 of the substrate forms a step with respect to the substrate. Thus, it is even more avoided to create mechanical stresses on the substrate 3.

[0052] It should also be noted that the zone 33 of the substrate 3 supporting the OLED 2 and the zone 34 of the portion 32 to which the card 6 is connected via the ACF connector 62, are distant from each other, being separated by a zone 35 of this portion 32. In order to prevent corrosive components of the double-sided adhesive layer from damaging the glass substrate 3, a part 53 of the double-sided adhesive strip located at this zone 35 was removed when this strip was cut.

[0053] It will be noted that the light module 1 can thus participate in the realization of a given photometric function, such as a direction indicator, a position light or even a reversing light. The light module 1 can be used alone or in combination with other identical light modules 1.

[0054] The foregoing description clearly explains how the invention makes it possible to achieve the objectives it has set itself, namely to propose a light module incorporating a flexible organic light-emitting diode and a flexible printed circuit board mechanically fixed to the module, without this fixing risking weakening the diode's protective substrate. These objectives are achieved in particular by decoupling the electrical connection and mechanical fixing functions, and by adding a portion to the protective substrate intended for the electrical connection and a portion to the diode support intended for the mechanical fixing.

[0055] In any event, the invention cannot be limited to the embodiments specifically described in this document, and extends in particular to any equivalent means and to any technically effective combination of these means. In particular, it may be provided that the protective substrate is made of a material other than glass, in particular of transparent plastic polymer. It may also be provided that the flexible printed circuit board is electrically connected to the organic light-emitting diode or to the transparent substrate by means of another type of connector.

Claims

Claims

1. Light module (1) of a lighting and / or signaling device for a motor vehicle, comprising: a. a flexible organic light-emitting diode (2) mounted on a transparent substrate (3), said transparent substrate comprising an interconnection layer comprising a network of electrical tracks intended for the electrical supply of the organic light-emitting diode; b. a support (4) for said flexible organic light-emitting diode, the support being arranged to conform at least a portion of the flexible organic light-emitting diode and the transparent substrate to a predetermined shape; said at least a portion of the organic light-emitting diode being fixed to the support by means of an adhesive (51); c. a flexible printed circuit board (6);

2.

3. characterized in that the transparent substrate has a portion (32) projecting from the organic light-emitting diode and facing a portion (43) of the support, in that the flexible printed circuit board is electrically connected to the interconnection layer at this portion of the transparent substrate and in that the flexible printed circuit board is fixed to this portion of the support by means of an adhesive (52); in that the adhesive (52) fixing the flexible printed circuit board (6) to the support (4) is identical to the adhesive (51) fixing the organic light-emitting diode (2) to the support and in that the adhesive (51, 52) is a layer of double-sided adhesive. Light module (1) according to the preceding claim, in which the layer of double-sided adhesive (52) fixing the flexible printed circuit board (6) to the support (4) and the layer of double-sided adhesive (51) fixing the organic light-emitting diode to the support (4) come from the same double-sided adhesive tape. Light module according to (1) one of the preceding claims, characterized in that the organic light-emitting diode (2) comprises a first light-emitting face (23), the transparent substrate (3) covering this light-emitting face, in that the organic light-emitting diode is mounted on the support (4) via a second face (24) opposite its first face, and in that the interconnection layer of the transparent substrate extends over the face (31) of the transparent substrate located on the side of the organic light-emitting diode.

4. Light module (1) according to one of the preceding claims, in which the network of electrical tracks of the interconnection layer is deposited on said face (31) of the transparent substrate located on the side of the organic light-emitting diode.

5. A light module (1) according to one of the preceding claims, wherein said flexible printed circuit board (6) is electrically connected to the interconnection layer by means of an anisotropic conductive adhesive type connector (62) arranged between an edge of said flexible printed circuit board and said portion (32) of the transparent substrate.

6. Light module (1) according to one of the preceding claims, characterized in that the flexible organic light-emitting diode (6) is mounted on a first zone (33) of the transparent substrate (3), in that the flexible printed circuit board (6) is electrically connected to the interconnection layer at a second zone (34) of the portion (33) of the transparent substrate, and in that the first zone and the second zone are separated by a third zone (35) of the portion of the transparent substrate, the light module being devoid of adhesive between the support (4) and the transparent substrate at the third zone.

7. Light module (1) according to one of the preceding claims, characterized in that said portion (43) of the support (4) forms a step with respect to the rest of the support.

8. Lighting and / or signaling device for a motor vehicle comprising a light module (1) according to one of the preceding claims.

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