Lighting device for a motor vehicle

Abstract

The present invention relates to a lighting device (100) for a motor vehicle, comprising at least: - a circuit board (1) with several light-emitting diodes (2), - a separator structure (3) arranged in front of the printed circuit board (1) and having a plurality of struts (30), wherein chambers are formed between the struts (30) and at least one light-emitting diode (2) is assigned to each chamber, - a diffuser foil (4) arranged in front of the separator structure (3) which is connected to the struts (30) by means of welded joints or by means of first adhesive joints (5a), and - an LC display (6) arranged in front of the diffuser film (4).

Description

[0001] The present invention relates to a lighting device for a motor vehicle and a method for its production. STATE OF THE ART

[0002] In the prior art, flat lighting devices based on a large number of light-emitting diodes are known as lighting means, which are used to carry out signaling functions in motor vehicles, for example as daytime running lights, tail lights, direction indicators or as front or rear signal lights for generating complex, dynamic light signals.

[0003] For example, the document DE 10 2021 129 672 A1 discloses a lighting device for a motor vehicle, comprising a circuit board with a plurality of light-emitting diodes arranged thereon, an optical disk, and a reflector element, wherein the reflector element is arranged between the circuit board and the optical disk, as well as a liquid crystal (LC) display arranged on the optical disk, which is configured to selectively switch partial areas ("pixels") between transparent and opaque states. The reflector element is divided into several segments, and each light-emitting diode is assigned a segment such that light emitted by the light-emitting diodes is reflected by the segments of the reflector element and backlit by the optical disk.The contour of the pixels of the LC display typically corresponds to the contour of the underlying segments, and by coordinating the switching of the LEDs and the LC display, sharp and high-contrast light signals can be dynamically generated.

[0004] The individual components of such lighting devices are typically only connected or clamped to one another at the edges, resulting in undesirable gaps between the components along the transverse planes of extension. This can lead to "crosstalk" between adjacent segments, meaning that light exiting an active segment is reflected multiple times into a neighboring inactive segment, which adversely reduces the sharpness and contrast of the displayed light signals. DISCLOSURE OF THE INVENTION

[0005] It is the object of the present invention to propose an alternative embodiment of a lighting device for a motor vehicle, which can in particular perform a signal light function with particularly sharp and high-contrast light signals.

[0006] This object is achieved by a lighting device according to claim 1. Advantageous developments of the invention are specified in the dependent claims.

[0007] The technical teaching of the invention discloses a lighting device for a motor vehicle, at least comprising: - a circuit board with several LEDs, - a separator structure arranged in front of the circuit board, which has a plurality of struts, wherein chambers are formed between the struts and each chamber is assigned at least one light-emitting diode, - a diffuser foil arranged in front of the separator structure, which is connected to the struts by means of welded joints or by means of first adhesive joints, and - an LC display arranged in front of the diffuser film.

[0008] The invention is based on the idea of sealing the individual chambers from one another and thus preventing unwanted crosstalk by sealing the chambers on the light exit side to the diffuser film arranged in front of them using welded or adhesive connections. This closes any gaps between the separator structure and the diffuser film, for example, due to dimensional deviations in the separator structure or folds in the diffuser film, thus creating a barrier to lateral light escape. The light emerging from the chambers is prevented from crossing into neighboring chambers, resulting in a sharply defined transition and high contrast between the active and inactive chambers in the backlight of the LCD display arranged in front of the diffuser film.

[0009] The separator structure is formed, in particular, from a plastic or a metal. The struts are attached to the front side of the circuit board and, forming the chambers, each enclose one or more light-emitting diodes, for example, light-emitting diodes of different light colors. The struts have light-absorbing or reflective surfaces that form the walls of the chambers. The contours of the chambers determined by the arrangement of the struts can be suitably dimensioned and shaped, for example, square, triangular, or forming a more complex freeform. The struts preferably have front-side end faces that form joining surfaces for the welded joints or the first adhesive joints.

[0010] The light from the LEDs emerging from the front of the chambers is scattered as it passes through the diffuser film, resulting in a flat, homogeneous light distribution that is sharply defined by the contour of the chambers and serves to backlight the LC display.

[0011] The individually switchable subregions ("pixels") of the LCD display, for example, have the same contour as the underlying chambers of the separator structure, or the LCD display has a finer subdivision. In particular, the LCD display is designed as a passive matrix display, in which the pixels are controlled passively via matrix control, i.e., without additional electronic components at the individual pixels. The active liquid crystal layer of the LCD display can, for example, be doped with black pigments, resulting in a black display in the opaque state.

[0012] In an advantageous embodiment of the lighting device, the struts are connected to the circuit board by means of second adhesive bonds, in particular by the struts having rear end faces that form joining surfaces for the second adhesive bonds. This prevents any gaps between the circuit board and the struts and prevents light from passing between adjacent chambers. Furthermore, the fixation of the struts prevents the formation of undesirable abrasion between the struts and the circuit board during practical operation of the lighting device. Suitable joining surfaces on the circuit board side include, in particular, the (tinned) copper surfaces or the carrier substrate, which can advantageously also absorb mechanical forces.

[0013] Another advantage is that the LCD display is connected to the diffuser film by means of third adhesive joints. The third adhesive joints serve, on the one hand, to prevent light emerging from the diffuser film at an oblique angle and / or reflected from the back of the LCD display from penetrating the area of adjacent "pixels". In addition, the third adhesive joints ensure that a gap necessary for light coupling is maintained between the diffuser film and the light entry surface of the LCD display, i.e. that the diffuser film does not come into direct physical contact with the LCD display. In particular, the third adhesive joints are arranged so as to overlap the welded joints or the first adhesive joints, so that the light exit areas defined by the contour of the chambers are not reduced by the third adhesive joints.

[0014] In particular, the welded joints, the first adhesive joints, the second adhesive joints, and / or the third adhesive joints are designed to be opaque and / or dust-impermeable. For example, the various adhesive joints can comprise an opaque adhesive.

[0015] Furthermore, the welded joints, the first adhesive joints, the second adhesive joints and / or the third adhesive joints preferably each completely surround all chambers so that a complete seal of the chambers is formed.

[0016] For example, the LC display has a non-planar, in particular curved, light entry surface. Such a design is made possible by the welded or adhesive connections introduced according to the invention, since these not only provide optical sealing but also increase the structural integrity of the lighting device, and a clamping effect to secure the separator structure and the diffuser film between the circuit board and the LC display is only required to a lesser extent. In production, an LC display with a curved light entry surface can preferably be realized by providing a separator structure with a corresponding front-side curvature. Such a separator structure mediates between the planar circuit board and the LC display, which is also initially provided in a planar form and only adopts the curved contour of the separator structure under pressure during assembly, thereby forming a robust laminate structure.Alternatively, a curvature of the LC display can be imposed during assembly using a separate device and fixed by the adhesive connections.

[0017] In particular, the lighting device is designed as a daytime running light, a tail light, a turn signal, a front signal light, or a rear signal light of a motor vehicle. The lighting device offers considerable design freedom for the detailed embodiments with regard to the segmentation of the individual "pixels" in combination with the LCD display. As a signal light, the lighting device can be designed to display various light images such as text, symbols, and graphics, as well as, for example, generate light signatures that dynamically adapt to the driving modes of the motor vehicle.

[0018] The invention further relates to a method for producing a lighting device according to one of the aforementioned embodiments, wherein the first adhesive bonds, the second adhesive bonds, and / or the third adhesive bonds are produced by screen printing (doctoring), jet printing, pin transfer, or tape (double-sided adhesive tape). In particular, the first adhesive bonds between the struts and the diffuser film, the second adhesive bonds between the circuit board and the struts, and the third adhesive bonds between the diffuser film and the LCD display are arranged in overlapping relationship, so that the same routine can be performed in each case when constructing the adhesive bonds layer by layer using screen printing, jet printing, or pin transfer.

[0019] Furthermore, the invention relates to a method for producing a lighting device according to one of the aforementioned embodiments, wherein the welded joints between the webs and the diffuser film are created by laser welding, ultrasonic welding, or vibration welding. For this purpose, the separator structure with the struts is provided, in particular, from a thermoplastic material. The struts preferably have front end faces that are suitable as flat joining surfaces for contacting the diffuser film and for forming the welded joints. EMBODIMENTS OF THE INVENTION

[0020] Further measures improving the invention are presented below, together with the description of exemplary embodiments of the invention, with reference to the figures. They show schematically: Fig. 1a: Cross-sectional view of a first embodiment of the lighting device according to the invention, Fig. 1b: Detailed view of the Fig. 1a, Fig. 2: Top view of a part of the first embodiment, and Fig. 3: Cross-sectional detail view of a second embodiment.

[0021] Fig. 1a shows a cross-sectional view of a first embodiment of the lighting device 100 according to the invention, and Fig. 1b shows a corresponding detailed view according to the Fig. 1a area marked with a dashed rectangle.

[0022] The lighting device 100 comprises the circuit board 1, which carries a plurality of light-emitting diodes 2 on the front and is connected to the heat sink 7 on the rear. The separator structure arranged in front of the circuit board 1 has the struts 30, with chambers formed between the struts 30, and each chamber is assigned a light-emitting diode 2. The diffuser film 4 arranged in front of the separator structure 3 is connected to the struts 30 by means of the first adhesive connections 5a. The LC display 6, which has two glass or plastic panes with a switchable liquid crystal layer between them, is arranged at a distance in front of the diffuser film 4.

[0023] The struts 30 have front end faces that form the joining surfaces of the first adhesive joints 5a. Due to the fixation by the adhesive joints 5a, the diffuser film 4 lies flat and wrinkle-free, thereby supporting homogeneous backlighting of the LC display 6. The diffuser film 4 is made of polycarbonate, for example, and has a thickness in the range of 0.1 - 0.5 mm. The adhesive joints 5a laterally seal the chambers formed between the struts 30 on the front side, so that light emitted by the LEDs 2, or even dust particles, cannot penetrate between the struts 30 and the diffuser film 4 into the adjacent chambers or their immediate vicinity.

[0024] The first adhesive joints 5a are designed to be impermeable to light and dust, in particular using an opaque adhesive, and the chambers are completely surrounded by the first adhesive joints 5a, ie the first adhesive joints 5a extend along the entire end faces of the struts 30.

[0025] Fig. Figure 2 shows a plan view of a part of the first embodiment, namely the separator structure 3 with the struts 30 forming the chambers and the associated light-emitting diodes 2. Due to the exemplary arrangement of the struts 30, the chambers have a triangular contour, ie, the "pixels" formed for backlighting the LC display are triangular. When constructing the welded joints or the first adhesive joints, the Fig. 2 exposed front end faces of the struts 30 are preferably used entirely as joining surfaces.

[0026] Fig. 3 shows a cross-sectional detail view of a second embodiment of the lighting device 100 according to the invention, wherein, in contrast to the first embodiment (cf. Fig. 1b) the struts 30 are connected to the circuit board 1 via their rear end faces by means of the second adhesive connections 5b and the LC display 6 is connected to the diffuser film 4 by means of the third adhesive connections 5c.

[0027] The third adhesive joints 5c are arranged to overlap the first adhesive joints 5a, so that the "pixels" formed for backlighting the LCD display 6 are not modified by the third adhesive joints 5c. Due to the third adhesive joints 5c, a well-defined gap exists between the diffuser film 4 and the rear light entry surface of the LCD display 6.

[0028] All adhesive joints 5a, 5b, 5c are light- and dust-tight and completely surround the chambers. In addition to completely sealing the chambers, the structure with the layered adhesive joints 5a, 5b, 5c also contributes to a significant increase in the stability of the lighting device 100. List of reference symbols 100 lighting devices 1 circuit board 2 LEDs 3 Separator structure 30 strut 4 diffuser film 5a first adhesive bond 5b second adhesive connection 5c third adhesive connection 6 LCD display 7 heat sinks QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 129 672 A1

[0003]

Claims

[1] Lighting device (100) for a motor vehicle, comprising at least: - a circuit board (1) with several light-emitting diodes (2), - a separator structure (3) arranged in front of the printed circuit board (1) and having a plurality of struts (30), wherein chambers are formed between the struts (30) and at least one light-emitting diode (2) is assigned to each chamber, - a diffuser foil (4) arranged in front of the separator structure (3) which is connected to the struts (30) by means of welded joints or by means of first adhesive joints (5a), and - an LC display (6) arranged in front of the diffuser film (4). [2] Lighting device (100) according to claim 1, characterized by that the struts (30) have front end faces which form joining surfaces of the welded joints or the first adhesive joints (5a). [3] Lighting device (100) according to claim 1 or 2, characterized bythat the struts (30) are connected to the circuit board (1) by means of second adhesive connections (5b). [4] Lighting device (100) according to claim 3, characterized by that the struts (30) have rear end faces which form joining surfaces of the second adhesive joints (5b). [5] Lighting device (100) according to one of the preceding claims, characterized by that the LC display (6) is connected to the diffuser film (4) by means of third adhesive connections (5c). [6] Lighting device (100) according to claim 5, characterized by that the third adhesive joints (5c) are arranged in overlap with the welded joints or the first adhesive joints (5a). [7] Lighting device (100) according to one of the preceding claims, characterized by that the welded joints, the first adhesive joints (5a), the second adhesive joints (5b) and / or the third adhesive joints (5c) are opaque. [8] Lighting device (100) according to one of the preceding claims, characterized by that the welded joints, the first adhesive joints (5a), the second adhesive joints (5b) and / or the third adhesive joints (5c) are designed to be dust-impermeable. [9] Lighting device (100) according to one of the preceding claims, characterized by that the first adhesive joints (5a), the second adhesive joints (5b) and / or the third adhesive joints (5c) comprise an opaque adhesive. [10] Lighting device (100) according to one of the preceding claims, characterized by that the welded joints, the first adhesive joints (5a), the second adhesive joints (5b) and / or the third adhesive joints (5c) each completely surround all chambers. [11] Lighting device (100) according to one of the preceding claims, characterized bythat the LC display (6) has a non-planar, in particular curved, light entry surface. [12] Lighting device (100) according to one of the preceding claims, designed as a daytime running light, a rear light, a direction indicator, a front signal light or a rear signal light. [13] Method for producing a lighting device (100) according to one of the preceding claims, characterized by that the first adhesive connections (5a), the second adhesive connections (5b) and / or the third adhesive connections (5c) are produced by means of screen printing, jet printing, pin transfer processes or by means of tape. [14] A method for manufacturing a lighting device (100) according to any one of claims 1 to 12, characterized by that the welded connections between the webs (30) and the diffuser film (4) are produced by means of laser welding, ultrasonic welding or vibration welding.

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