DE102011055430B4 - Light module for the generation and transmission of light - Google Patents

Abstract

Light module (10) for generating and transmitting light, comprising a light guide (20) and a light source (30) with at least one LED (32), wherein the light guide (20) has at least one coupling surface (22) for coupling the light generated by the light source (30) into the light guide (20), characterized in that the coupling surface (22) is provided at least in sections with a filter layer (40) which prevents the coupling of light from the light source (30) into the light guide (20) in a defined wavelength range, wherein the defined wavelength range defines a range with wavelengths of less than or equal to 420 nm and of greater than or equal to 380 nm.

Description

The present invention relates to a light module for generating and transmitting light and to a headlight for a vehicle, comprising at least one such light module.

Light modules for generating and transmitting light are generally known. They often have at least one light source with at least one light source, usually in the form of an LED. In addition, such light modules often have a light guide, which is equipped with at least one coupling surface for coupling the light generated by the light source into the light guide. In other words, the coupling surface serves to couple the light into the light guide in order to be able to conduct the light there as desired.

A disadvantage of known light modules is that the long-term stability of the light guide is a critical point in the service life of such a light module. In particular, material defects in the light guide arise over a long service life of such light modules. It has already been determined that high temperatures in particular, which arise when the light source in the form of LEDs is operated, can impair the material of the light guide and in particular make it unusable. In order to remedy this disadvantage, it is already known to manufacture light modules from appropriate temperature-resistant materials, such as glass. However, this leads to relatively expensive light modules, which also have limitations in terms of their lighting properties and the bendability of such glass light guides. For example, in the DE 102 05 694 A1 or the WO 2008/ 011 938 A1 It has already been proposed that light guides be made from different materials and that these be combined. The areas with the coupling surface can be made of a high-temperature-resistant material such as glass, for example, while the rest of the light guide is made of a more cost-effective plastic. The disadvantage of these embodiments is that contact surfaces are created between the different materials, which are difficult to handle in terms of lighting technology. In addition, the different refractive indices of the different materials of the light guide must be taken into account when arranging the lighting technology of such a light module, and appropriate measures must be taken. This increases the complexity of manufacturing and designing such light modules many times over. It has also been found that known light modules are subject to material wear, regardless of temperature influences. In particular, it was surprisingly discovered that short-wave light from the light sources can be the cause of material wear on the light guide. This leads in particular to failures that can only be prevented or minimized by a particularly large distance between the light source and the coupling surface in order to achieve the desired long-term stability.

From the US 6 637 905 B1 A method and system for providing backlighting using a luminescent impregnated material are known. The US 2008/0025045 A1 discloses a structure for improving the brightness of the side LCD backlight module. The WO 2006/003595 A1 discloses a lighting system for a vehicle headlight unit. EP0778440A2 is a backlit color display. The US 2006/0002131 A1 discloses a phosphor-based lighting system with multiple light guides and a display using the same. The US 5,882,774 A relates to optical films that are useful, for example, as polarizers and/or mirrors.

It is the object of the present invention to at least partially eliminate the disadvantages of known light modules described above. In particular, it is the object of the present invention to provide a light module and a headlight for a vehicle which provide the desired long-term stability in a maintenance-free manner.

The above object is achieved by a light module with the features of independent claim 1 and by a headlight with the features of independent claim 8. Further features and details of the invention emerge from the subclaims, the description and the drawings. Features and details that are described in connection with the light module according to the invention naturally also apply in connection with the headlight according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other.

A light module according to the invention for generating and transmitting light has a light guide and a light source with at least one LED. The light guide is provided with at least one coupling surface for coupling the light generated by the light source into the light guide. In this way, a separation of the desired exit location for the light and the generation of the light by the light source can be provided.

A light module according to the invention is characterized in that the coupling surface is provided with a filter layer at least in sections. This filter layer prevents light from the light source from being coupled into the light guide in a defined wavelength range. In other words, the filter layer serves to "cut out" part of a wavelength spectrum and prevent it from affecting the light guide. Preferably, a wavelength range is filtered out in a defined manner which has been identified as the main cause of material-technical damage to the material of the light guide. These are areas in a wavelength range below 420 nm. In particular, the area around 400 nm has surprisingly been identified as a damaging area, so that the use of such a filter surprisingly leads to a strong increase in the long-term use stability of a light module.

Preferably, the wavelength range is defined in such a way that more or less exclusively only those wavelengths are filtered out that are not necessary or only necessary to a small extent for the desired visible light function. For example, if one or more LEDs are used as a light source, they have a broad light spectrum over a large number of different wavelength ranges. The shortest wavelength range is the so-called blue peak. The falling area of the blue peak in the direction of shorter wavelength ranges is a marginal area of the entire spectrum of the LED, which is associated with high energy output, but is of little importance for the desired visible light function. In this respect, a light module according to the invention makes it possible to filter out this marginal area and in this way to reduce or completely prevent a damage mechanism with little or no impairment of the quality of the light function. This has the particular advantage that in modern vehicles there is often a desire for such a light module to be maintenance-free. In particular, the light module should exceed the service life of the vehicle in a continuous use situation. In particular, an individual replacement of such light modules is not desired. By means of an embodiment of a light module according to the invention, a crucial failure mechanism for the light guide can be brought under control, so that the long-term stability can be significantly increased. This makes significantly longer service lives possible for a light module according to the invention than can be achieved with known light modules.

A further advantage of light modules according to the invention is that it is possible to reduce the distance between the light source and the coupling surface. Due to the fact that the distance between the light source and the coupling surface is proportional to the damaging effect on the light guide caused by the radiation emitted by the LED, the increased protection provided by the filter layer makes it possible to reduce the distance. The reduction in the distance is a great advantage because the lighting coupling and optical processing of the light generated by the light source is significantly simplified in this way. In addition, the overall installation space of the light module is reduced, which is a great advantage for any use in vehicles. In particular, distances of less than 3 mm are provided. Even significantly smaller distances of less than 1 mm, less than 0.8 mm, less than 0.5 mm or up to distances of 0.1 to 0.3 mm are only possible with an embodiment of a light module according to the invention.

A light source for a light module according to the invention can of course have one or more LEDs. Individual LEDs can also be provided with different colors, so that they are critical and non-critical LEDs with regard to the wavelength spectra emitted. Since the filter layer covers the coupling surface at least in sections, a correlation with the individual colors of the LEDs can preferably be carried out here. It is therefore sufficient if a filter layer according to the invention is only provided in the sections of the coupling surface which correlate with LEDs that emit the defined wave range, i.e. the damaging wavelength range. "Harmless" LEDs can be left out in this way, so that the filter layer can be reduced to the absolutely necessary minimum in terms of its geometric extension. In addition to reducing costs, the influence of the coupled light from a lighting point of view can also be reduced to a minimum.

Preventing the coupling of light from the light source in a defined wavelength range in the light guide is understood to mean, in particular, preventing coupling from a technical point of view. From a technical point of view, coupling is prevented when a significant reduction in wavelengths occurs through this filter. Complete filtering, i.e. 100 percent filtering, is not necessarily necessary to achieve this. Lower filter values, in particular a reduction of 80 percent or at least 70 percent, are also possible within the scope of the present invention in order to achieve a corresponding to form a suitable filter layer that prevents coupling into the light guide for the defined wavelength range.

In the light module according to the invention, the filter layer prevents light from the light source with a wavelength of less than or equal to 420 nm from being coupled into the light guide. In other words, the wavelength of 420 nm represents an upper limit that is above 400 nm. In particular, the upper limit is set at 415 nm, particularly preferably at 410 nm. The range around 400 nm has surprisingly been found to be a range with particularly high damage to the material of the light guide. The lower the upper limit is set, the more precisely the damaging wavelength ranges can be cut out. In particular, the filter is focused on wavelength ranges that only have a small share in setting the color of a light function. The lower this upper limit is chosen, in particular at 415 or 410 nm, the less the light color is influenced in an undesirable way. However, the higher this upper limit is set, the better the filter function and the greater the increase in long-term stability for the light module.

In the light module according to the invention, the filter layer prevents light from the light source with a wavelength greater than or equal to 380 nm from being coupled into the light guide. This is in particular the lower limit of the defined wavelength range to be filtered. This lower limit can of course also be higher, for example at 385 nm or preferably at 390 nm. In combination with the statements in the previous paragraph, one can therefore speak of a filter range or a defined wavelength range around 400 nm. The spectrum below this is usually designed in such a way that the LED no longer has any share there. The lower limit is also not critical with regard to influencing the lighting technology. Rather, the lower limit is relevant with regard to the choice of filter coating, so that an increase in the lower limit allows more cost-effective and simpler materials for the filter layer.

• - Polycarbonat (PC),
• - Polymethylmethacrylat (PMMA),
• - Polymethacrylmethylimid (PMMI),
• - Cyclo-olefinisches Copolymer (COC),
• - Cyclo-olefinisches Polymer (COP).

A further advantage is when, in a light module according to the invention, the light guide consists of a plastic material which in particular comprises one of the following materials:

• - Polycarbonate (PC),
• - Polymethyl methacrylate (PMMA),
• - Polymethacrylmethylimide (PMMI),
• - Cyclo-olefinic copolymer (COC),
• - Cyclo-olefinic polymer (COP).

A typical material here is polycarbonate and its mixtures. A light module according to the invention will bring great advantages, particularly with plastic materials such as those specified in the above list. In particular, by filtering out the defined wave ranges, changes to the polymer structure, in particular so-called "cracking" or degeneration of the polymer structure, can be prevented. This generates a protection that postpones or reduces or completely prevents the coupling surface from becoming blind and thus a complete or partial failure of the light module to a later point in time.

A further advantage is when, in a light module according to the invention, the filter layer has a sharp delimitation of the defined wavelength range for the filter property, the edges of which in particular have a resolution of less than or equal to 5 nm. Broader resolution edges of up to 10 nm are of course also possible. This means that the filter jump between the filtered and unfiltered area is implemented as a very steep filter jump. In other words, sharp-edged filtering is possible. The filtered area differs very significantly from the unfiltered area, so that there is only a very small transition area. This makes it possible to specifically filter out a certain predefined wavelength range, so that a small transition area also has little influence, for example, on the color of the light function. A conscious difference between desired and undesired wavelengths can therefore be provided by a filter layer according to the invention.

Within the scope of the present invention, it is also advantageous if the distance between the light source and the coupling surface is less than or equal to 1 mm, in particular less than or equal to 0.8 mm, preferably less than or equal to 0.5 mm and particularly preferably less than or equal to 0.3 mm. This is made possible in particular by an embodiment of a light module according to the invention and the provision of the filter layer. The smaller the distances, the better the lighting coupling into the lighting technology is possible. In particular, optical projections can be dispensed with, since almost direct contact between the light source and the coupling surface is possible.

In a light module according to the invention, the filter layer can have a temperature resistance that is greater than or equal to 120° C. Since high temperatures of up to over 100° C, in particular up to 120° C, can often be reached when using LEDs, a temperature-resistant A permanent filter layer is a great advantage, as the filter layer's properties provide the necessary durability for the light module. Of course, the LEDs are also designed for temperature resistance and are preferably provided with passive or active heat sinks, which can also be designed as part of the light module.

A light module according to the invention can preferably be designed such that the coupling surface is essentially flat. This reduces the effort required to manufacture the light module and in particular the effort required to coat the coupling surface with the filter layer. A substantially flat coupling surface also serves to reduce the influence of the lighting technology when coupling in the light generated by the light source to a minimum.

Alternatively or additionally, it is also possible for the coupling surface to have a concave curvature, at least in sections. This allows an even smaller distance between the coupling surface and the LED. In terms of lighting technology, this has the advantage that long-term stability is also achieved at particularly small distances. The concave curvature is already a first part of influencing the light and can be improved by additional optical components.

In a light module according to the invention, it is possible for the filter layer to have a layer thickness of at least 5 µm. This minimum layer thickness is chosen in particular with reference to the long-term stability and the desired filter performance. Depending on the actual material selected for the filter layer, thicker layer thicknesses can of course also be used. The filter layer is applied, for example, by a printing process, in particular by pad printing. Spray coatings or coating by immersion are also possible in order to achieve the desired filter layer on the coupling surface of the light module for the light guide.

The present invention also relates to a headlight for a vehicle, comprising at least one light module according to the invention. A headlight according to the invention thus brings with it the same advantages as have been explained in detail with reference to a light module according to the invention.

• 1 eine Darstellung eines Lichtmoduls einer ersten Ausführungsform,
• 2 eine Darstellung eines Details eines Lichtmoduls einer zweiten Ausführungsform,
• 3 eine Darstellung eines Details eines Lichtmoduls einer dritten Ausführungsform,
• 4 eine Ausführungsform eines Wellenlängenspektrums für eine LED, und
• 5 eine Ausführungsform einer Filterschicht hinsichtlich der Filtereigenschaft.

The invention is explained in more detail using the attached drawings. The terms "left", "right", "top" and "bottom" used refer to an alignment of the drawings with normally legible reference symbols. They show schematically:

• 1 a representation of a light module of a first embodiment,
• 2 a representation of a detail of a light module of a second embodiment,
• 3 a representation of a detail of a light module of a third embodiment,
• 4 an embodiment of a wavelength spectrum for an LED, and
• 5 an embodiment of a filter layer with regard to the filter properties.

The 1 to 3 show various embodiments of a light module according to the invention. The 2 and 3 show detailed sections of such a light module 10.

In 1 an embodiment of a light module 10 according to the invention is shown, in which a light source 30 is provided with five LEDs 32. On the back of the light source 30, a heat sink 50 is provided, which is provided as a passive heat sink with cooling fins that serve to cool the LEDs 32. A light guide 20 is arranged in a circle above the light source 30. The light guide 20 is provided with a coupling surface 22 via which light can be coupled in, which is generated by the LEDs 32 of the light source 30. In order to protect this coupling surface 22 from the aggressive radiation of the LEDs 32, a filter layer 40 is provided on the coupling surface 22. In this embodiment, the filter layer 40 extends essentially over the entire coupling surface 22 and protects it in this way. Light emitted by the light source 30 only passes through the filter layer 40 to the coupling surface 22 and can be coupled there into the light guide 20. The filter layer 40 serves to filter out defined wavelength ranges. The filter layer 40 is preferably designed in such a way that it filters out a wavelength range around 400 nm. Since this range has surprisingly proven to be particularly aggressive with regard to a change in the material of the light guide 20, the long-term stability of the light guide 20 and thus of the entire light module 10 is significantly increased in this way. The light guide 20 is preferably made of a plastic material, for example polycarbonate or polycarbonate with additional components.

In the 2 and 3 Further variants of the possible coupling of light for a light module 10 are shown. In 2 a substantially planar embodiment of the coupling surface 22 is shown, which is provided with a filter layer 40 only in a certain section. This is advantageous, for example, if only the three left LEDs 32 have a wavelength spectrum that is damaging to the material of the light guide 20. For example, the two right LEDs 32 of the light source 30 are designed without such a damaging spectrum component. In this embodiment, it is sufficient if the filter layer 40 only extends over the section that couples in the light from the three left LEDs 32 of the light source 30. This significantly reduces the costs and effort for coating with the filter layer 40.

In 3 1 shows a further embodiment of the light module 10. There, a curved coupling surface 22 is provided, which already has a collecting effect on the light provided by the light source 30. The curved coupling surface 22 is again provided with the filter layer 40 essentially over its entire surface. The filter layer 40 can preferably also be curved, as is the case with the 3 However, other coating forms, in particular coating forms of the filter layer 40, which do not reflect the surface structure and curvature of the coupling surface 22, are also conceivable within the scope of the present invention.

In 4 is an example of a wavelength spectrum of an LED. This defines a filter range with F, which is the lower edge of the peak. The peak on the left in the wavelength spectrum is, for example, the blue peak of an LED. The drop as the wavelength decreases is a region in particular that no longer has a great influence on the function of the light, particularly with regard to the color. However, there is a high energy density for the corresponding wavelength in this region, so that filtering in this region without greatly influencing the color of the light function represents great protection for the light guide 22.

5 shows a possible way of filtering through a filter layer 40. Here, a particularly sharp demarcation between the filtered and the unfiltered area is provided by the filter layer 40. B is to be understood as the demarcation width of the filter property. In other words, a particularly small transition area is provided with regard to the wavelength, so that the degree of transmission essentially jumps back and forth between the filtered and the unfiltered area. This makes it possible to distinguish precisely and consciously between a filtered and an unfiltered area, i.e. between the defined wavelength range for the filter layer 40 and other wavelength ranges.

It goes without saying that the above statements on the individual embodiments describe the invention only in the context of examples. Accordingly, individual features can be freely combined with one another, provided they are technically expedient, without departing from the scope of the present invention.

List of reference symbols

10

Light module

20

Light guide

22

Coupling surface

30

Light source

32

LED

40

Filter layer

50

Heatsink

B

Delimitation width of the filter property

F

Filter area

Claims (8)

Light module (10) for generating and transmitting light, comprising a light guide (20) and a light source (30) with at least one LED (32), wherein the light guide (20) has at least one coupling surface (22) for coupling the light generated by the light source (30) into the light guide (20), characterized in that the coupling surface (22) is provided at least in sections with a filter layer (40) which prevents the coupling of light from the light source (30) into the light guide (20) in a defined wavelength range, wherein the defined wavelength range defines a range with wavelengths of less than or equal to 420 nm and of greater than or equal to 380 nm. Light module (10) according to one of the preceding claims, characterized in that the light guide (20) consists of a plastic material which in particular comprises one of the following materials: - polycarbonate (PC), - polymethyl methacrylate (PMMA), - polymethacrylmethylimide (PMMI), - cyclo-olefinic copolymer (COC), - cyclo-olefinic polymer (COP). Light module (10) according to one of the preceding claims, characterized in that the filter layer (40) has a sharp delimitation of the defined wavelength range for the filter property, the edges of which in particular have a resolution of less than or equal to 5 nm. Light module (10) according to one of the preceding claims, characterized in that the distance between the light source (30) and the coupling surface (22) is less than or equal to 1 mm, in particular less than or equal to 0.8 mm, preferably less than or equal to 0.5 mm and particularly preferably less than or equal to 0.3 mm. Light module (10) according to one of the preceding claims, characterized in that the coupling surface (22) is substantially flat. Light module (10) according to one of the Claims 1 until 4 , characterized in that the coupling surface (22) has a concave curvature at least in sections. Light module (10) according to one of the preceding claims, characterized in that the filter layer (40) has a layer thickness of at least 5 µm. Headlight for a vehicle, comprising at least one light module (10) with the features of one of the Claims 1 until 7 .

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