DE102007015747A1 - Optical fiber arrangement for mounting device for illuminating retroreflecting vehicle number plate, has laminar expanded transparent optical fiber with front side light transmission surface and rear side light transmission surface - Google Patents

Abstract

The optical fiber arrangement (5) has a laminar expanded transparent optical fiber (80) with a front side light transmission surface and a rear side light transmission surface. The optical fiber has light decoupling structures which are arranged in the area of the light transmission surface. The light decoupling structure has a light decoupling degree depending on the direction of travel of the light guided in the optical fiber. An independent claim is also included for a method for the production of a optical fiber arrangement for illuminating retroreflecting vehicle number plate.

Description

object The present invention is a light guide assembly for illumination a mounted on a motor vehicle retroreflective license plate with the features of the preamble of claim 1. Furthermore the present invention a method for producing a light guide assembly as well as advantageous applications of the invention Optical fiber arrangement.

Optical fiber arrangements for illuminating a vehicle license plate attached to the motor vehicle are known per se from the prior art. So revealed the JP 2004 062139 A a light guide arrangement in which a light diffusion layer is arranged on a light passage surface of a planarly extended transparent light guide, which consists of two or more light-transmitting materials with different refractive indices. The light diffusion layer is provided for coupling out light guided in the optical waveguide and for illuminating a license plate behind the optical waveguide. An equivalent arrangement is also from the DE 102 584 65 A1 of the same applicant.

adversely at the previously known from the prior art photoconductor based Lighting device for a license plate is however, that the lighting device by design not suitable for retroreflective license plates is. This is due to the fact that the stand out Although the prior art lighting device, a right Good illumination of the license plate is achieved, as a rule However, the light guide based illumination device increases low transmission values for the held license plate incident light, so that compliance with the currently applicable statutory regulations for retroreflectivity of the held license plate for usual retroreflective license plates are not guaranteed is. Usual retroreflective license plates are based today on the use of retroreflective sheeting that based on high-index glass spheres embedded in a film, the back are mirrored. Even though this retroreflective sheeting already have a very good retroreflectivity, such is the weakening of retroreflected light, the when passing through a lighting device according to the State of the art occurs so great that the legal Rules for the retroreflectivity of a License plate usually no longer achievable are.

task The present invention is therefore an illumination device for a retroreflective license plate, which has such good transmission values that the legal Regulations for the retroreflectivity of the held Illuminated retroreflective license plate among all guaranteed in practical circumstances.

Further The object of the present invention is a mounting device for fixing a retroreflective license plate indicate on a motor vehicle, which is an inventive Optical fiber assembly comprises.

Farther It is an object of the present invention to provide a process for the preparation specify a light guide assembly according to the invention.

Solved This object is achieved by a light guide arrangement according to claim 1, by a mounting device according to claim 13 and by a method according to claim 16.

A Light guide arrangement according to the invention for illumination a vehicle-mounted retroreflective license plate comprises a planar, extended transparent light guide, the one front and one back light passage surface having. Furthermore, the light guide arrangement comprises at least one Light source whose light is coupled into the light guide. The coupled light is in the optical fiber in a running direction L led and to the illumination of the behind the light guide assembly targeted to be arranged retroreflective license plate decoupled from the light guide. For this purpose, the light guide in Area of a light passage surface arranged Lichtauskoppelstrukturen which serve the purpose that in the light guide by means of internal Total reflection guided light locally from the light guide to decouple and to illuminate the retroreflective license plate to steer towards this.

According to the invention, it is now provided that the light outcoupling structures, which are arranged in the region of at least one light passage surface, have a light output ratio dependent on the running direction L of the light guided in the light guide. In practice, this means that the light extraction structures in a first running direction L1 of the light in the optical waveguide very effectively decouple the light guided in the optical waveguide, but only a very small one in a second running direction L2 which is preferably orthogonal to the first running direction L1 Have coupling efficiency.

there The invention is also surprising for the expert Based on knowledge that Lichtauskoppelstrukturen with the aforementioned Properties can be manufactured so that the law prescribed retroreflective values for by means of the invention Optical fiber assembly illuminated retroreflective license plate under all practical circumstances. This is due to the fact that the legal requirements state that the prescribed for a wide angle range Retroreflectivity of the retroreflective license plate must be given only in one plane, namely when irradiated of the light to be reflected in a plane parallel to the earth's surface is oriented. Perpendicular to this level play the achieved Retroreflective values, on the other hand, only play a minor role.

in the Extensive experimental investigation has now been established be that light extraction structures, as they are for the Light guide assembly according to the invention provided are, in fact, over a wide angular range achievable retroreflectance values of the held and illuminated retroreflective license plate in one direction only influence so strongly that compliance with the law Retroreflective values for a measurement in this level are not below be guaranteed in all circumstances. at By contrast, retroreflectivity becomes a measurement in an orthogonal plane held and by the invention Light guide assembly illuminated retroreflective license plate practically only slightly weakened, so that practically equipped with all commercial films retroreflective Motor vehicle signs under all practical circumstances the legal Meet specifications regarding their retroreflectivity. The at a measurement in this "preferred reflection plane" still occurring weakening of retroreflectivity The license plate has its cause practically only in the reflectivity of the undisturbed air-optical interface itself, for visible light in the range of 4% per pass through an interface.

These For the expert amazing knowledge lies essentially in that the transmissivity the light guide on which the inventive Fiber optic arrangement is based on irradiation of the light in one first level (the "preferred level") very little a planar light guide is disturbed. In a perpendicular to it Direction of irradiation, on the other hand, becomes the transmittance of the light guide significantly more impaired. Comparable effects also arise with regard to the contrast the license plate legend when viewed through the same the light guide of a light guide assembly according to the invention therethrough.

In order to the advantages of the proposed invention Fiber optic arrangement must be realized in addition to a suitable Selection of lichtauskoppelnder structures practically only guaranteed be that the lichtauskoppelnden structures in a proper Use of the light guide arrangement according to the invention are oriented so that the legally required retroreflective values for the illuminated by the light guide assembly retroreflective license plate, d. H. that the "preferred plane" of the light guide assembly is correctly oriented.

Such directional dependent, d. H. anisotropic decoupling degrees in the region of at least one light passage area of the Fiber optic arranged Lichtauskoppelstrukturen can be realized, for example, that the Lichtauskoppelstrukturen transverse to the direction L significantly larger geometric dimensions than in the running direction L. In particular, it has as Advantageously, when the geometric dimensions of the Lichtauskoppelstrukturen transverse to the direction L at least to the Factor 10, preferably by a factor of 100, particularly preferably by the Factor 1000 or more, larger than the geometric ones Dimensions in the direction L.

Especially it is easy to generate corresponding light extraction structures, if the areal extended optical fiber from a transparent plastic such as polycarbonate or PMMA. Especially In this case, the Lichtauskoppelstrukturen can be as with make the optical fiber formed geometric structures. In particular, the light extraction structures can be considered raised or recessed structures formed on at least one Light transmission surface are formed. In the context of the embodiments will be more specific to various advantageous embodiments of Lichtauskoppelstrukturen be received, which is a realization allow the advantages of the invention.

An existing from a transparent plastic planar extensive light guide can be produced in a very simple manner by injection molding, which has the further advantage that the invention be provided in the region of a light passage surface Lichtauskoppelstrukturen in the simplest way can be formed during injection molding of the light guide in the light passage surface. This will also be discussed in more detail in the context of the following embodiments.

In An alternative approach is the invention Light extraction structures not as geometric structures in the area a light passage surface formed, rather they are formed by anisotropic scattering particles that are oriented in the light guide are introduced.

It has proved to be particularly advantageous if the present invention in Form at least one light passage area Lichtauskoppelstruktur a proportion of a maximum of 20% of the surface cover the light passage area, in whose area they are arranged. Preferably, the cover Light extraction structures account for a maximum of 10% of the surface, most preferably a maximum of 5% of the surface of the light guide or less.

One Another aspect of the present invention is a mounting device for fixing a retroreflective license plate on a car. The mounting device comprises a holder, the adapted to a retroreflective license plate to hold with a two-dimensional shield plate. The holder itself is intended to be attached to a motor vehicle so that the holder held retroreflective license plate is determined mechanically on the vehicle.

The mounting device further comprises a light guide assembly according to claim 1, wherein the light guide of the light guide assembly is arranged with the retroreflective license plate mounted on the front side of the planar expanded shield plate of the held retroreflective license plate. Particularly suitable here is the use of a holder, as it is apparent from the DE 10 2005 035 232.4 which is also the property of the assignee of the present application. The mounting device according to the invention can be realized, for example, by the previously known from the aforementioned German patent application holder for a license plate is combined with the light guide assembly, which is the subject of claim 1 of the present application. This will also be discussed in more detail in the context of the embodiments.

One Another object of the present invention is an illuminable retroreflective license plate arrangement incorporating a retroreflective license plate with a surface extended shield plate and a light guide assembly according to the Claim 1 of the present application comprises. Here is the light guide the light guide assembly so the front side of the areal Extended shield plate of retroreflective license plate arranged that the license plate from the light guide assembly is illuminated.

One Another object of the present invention is a motor vehicle, which with an illuminated holding device for a retroreflective license plate is equipped. The Holder device of the vehicle has a license plate holder which is adapted to a retroreflective license plate with a planar extended shield plate so too Keep that this is determined mechanically on the car. Farther the holding device comprises a light guide arrangement according to the Claim 1 of the present application. Will a license plate taken from the covered license plate holder, so is the light guide of the further included light guide assembly front of the areal extended shield plate of retroreflective License plate arranged. This aspect of the present The invention particularly includes motor vehicles with specially trained Body, which is a holding device with the aforementioned features formed. Examples of this could be integration such a holding device in the boot lid or the Bonnet of the motor vehicle, the holding device could but also an integral part of bumpers be of the motor vehicle.

• a) Bereitstellen zumindest einer Lichtquelle,
• b) Bereitstellen eines flächenhaft ausgedehnten transparenten Lichtleiters mit einer frontseitigen Lichtdurchtrittsfläche und einer rückseitigen Durchtrittsfläche, wobei der Lichtleiter im Bereich zumindest einer Lichtdurchtrittsfläche angeordnete Lichtauskoppelstrukturen aufweist, die ein Auskoppelvermögen für im Lichtleiter mittels interner Totalreflexion geführtes Licht aufweist, welches von der Laufrichtung L des Lichts im Lichtleiter abhängig ist,
• c) Herstellen einer optischen Verbindung zwischen der Lichtquelle und dem flächenhaft ausgedehnten Lichtleiter dergestalt, dass das von der Lichtquelle ausgesandte Licht in den Lichtleiter eingekoppelt wird und in einer Laufrichtung L durch interne Totalreflexion in diesem geführt wird.

The method, which solves the problem formulated above, serves to produce a light guide arrangement for illuminating a retroreflective license plate mounted on a motor vehicle. The method according to the invention comprises the following method steps:

• a) providing at least one light source,
• b) providing a planarly extended transparent light guide having a front light passage surface and a rear passage surface, wherein the light guide in the region of at least one light passage surface disposed Lichtauskoppelstrukturen having a Auskoppelvermögen for guided in the optical fiber by total internal reflection light, which from the running direction L of the light in Optical fiber is dependent,
• c) producing an optical connection between the light source and the areally extended light guide in such a way that the light emitted by the light source is coupled into the light guide and in a running direction L is guided by total internal reflection in this.

there can the provided in process step b) areal extended transparent light guide part of a light guide assembly according to claim 1 or according to one of the subordinate claims 2 to 12 be.

in the It has the scope of the method according to the invention proved to be particularly advantageous when the light guide by injection molding from a transparent plastic will be produced. In this case, it is possible in particular the light output structure to be provided according to the invention, in the area of at least one of the two light transmission surfaces are to be arranged, during the injection molding process itself in the light transmission surfaces to mold.

• 1. eine ausreichende Retroreflektivität des gehaltenen Schilds unter allen Umständen sichergestellt ist,
• 2. das gehaltene Schild von der integrierten Beleuchtungseinrichtung unter allen Umständen so ausgeleuchtet wird, dass es ohne Fremdbeleuchtung ausreichend gut abzulesen ist.

The following basic considerations are based on the present invention. The one from the DE 102 58 465 A1 known holder is not intended to hold and illuminate a retroreflective shield, in particular license plate, so that

• 1. sufficient retroreflectivity of the held sign is ensured in all circumstances,
• 2. The held sign is illuminated by the integrated lighting device in all circumstances so that it is sufficiently easy to read without external lighting.

task The present invention is therefore an illumination device of the aforementioned type for a retroreflective shield Specifically, for illuminating a retroreflective License plate is suitable, in their use always a sufficient Retroreflectivity of the held shield ensured is, and in their use, the retroreflective shield of the integrated lighting device is illuminated so that Always read it well enough without further external lighting is.

Farther It is the object of the present invention to provide a shield arrangement from a lighting device and a retroreflective Give a sign indicating that the sign is always well lit. and has a minimum level of retroreflectivity.

• • die durch die Ausleuchtung des retroreflektierenden Schilds erzielte Abstrahlung der Schildanordnung mindestens 2 Candela pro Quadratmeter beträgt, und
• • die Retroreflektivität des retroreflektierenden Schilds durch die die Beleuchtungseinrichtung um maximal 60%, bevorzugt um nicht mehr als 30% reduziert wird.

An illumination device according to the invention for a retroreflective sign with a legend comprises a planarly extended light guide which is intended to be arranged on the front side of the retroreflective shield to be illuminated in order to homogeneously illuminate the retroreflective shield by coupling out light guided in the light guide. According to the invention, the illumination device is designed such that

• • the radiation emitted by the retroreflective shield is at least 2 candela per square meter, and
• • the retroreflectivity of the retroreflective shield by which the illumination device is reduced by a maximum of 60%, preferably by not more than 30%.

• • Lichtleitermaterial und -geometrie
• • Anzahl, Anordnung und Lichtstärke der Lichtquellen,
• • Ankopplung der Lichtquellen an den Lichtleiter,
• • Auskoppelstärke des Lichtleiters, einschließlich deren räumlicher Verteilung,
• • Transmission durch den Lichtleiter,
• • Abschwächung des Kontrasts eines auszuleuchtenden retroreflektierenden Schilds.

This is achieved by a targeted coordination of the relevant parameters of the lighting device, which include the following:

• • Fiber optic material and geometry
• Number, arrangement and light intensity of the light sources,
• Coupling of the light sources to the light guide,
• Decoupling strength of the optical fiber, including its spatial distribution,
• Transmission through the optical fiber,
• • Reducing the contrast of a retroreflective sign to be illuminated.

Prefers the radiation is one of an inventive Lighting device illuminated sign at least 2.5 candela per square meter.

Farther is the reduction in retroreflectivity of the retroreflective Shield through which the illumination device preferably in the area from 5 to 50%, more preferred is a range of from 1.5 to 30%.

A shield assembly according to the invention comprises a retroreflective shield with a legend and a lighting device. The illumination device comprises a planarly extended light guide, which is arranged on the front side of the retroreflective shield to be illuminated. The light guide is provided to the retroreflective shield by coupling out of guided in the light guide light to illuminate as homogeneously as possible. According to the invention, the illumination device is designed such that the radiation of the shield arrangement achieved by the illumination of the retroreflective shield is at least two candels per square meter. Preferably, the radiation of the illuminated sign is at least 2.5 candela per square meter.

Farther the lighting device is designed so that the retroreflectivity the shield arrangement at least 20 candela per lux and square meter is preferably above 25 candela per lux and Square meters and more preferably over 30 candela per Lux and square meters.

• • Retroreflektivität des retroreflektierenden Schilds,
• • Kontrast der Legende des retroreflektierenden Schilds

The said remaining retroreflectivity and illumination of the retroreflective shield is achieved by a suitable choice of the parameters mentioned in the characterization of the illumination device according to the invention and at least the following further parameters:

• Retroreflectivity of the retroreflective shield,
• • Contrast of the legend of the retroreflective shield

The Invention is thus based to a significant extent on the knowledge that that by a suitable vote of the aforementioned parameters successively the achievable luminosity of the retroreflective to be illuminated Schilds, the remaining retroreflection and the readability of the Legend of the shield can be adjusted so in particular a use of the illumination device and / or the shield assembly for a retroreflective license plate.

The Invention is particularly suitable for retroreflective License plate, but it is not limited to this. Rather, the invention is basically for use suitable for all types of retroreflective shields to be illuminated by an external light source. Examples of this are traffic signs, advertising signs in public space or also display or advertising facilities called on motor vehicles such as buses, trains or trucks.

in the Related to retroreflective license plates the lighting device according to the invention with to be used on all types of license plates, e.g. B. with License plates with or without embossed legend or with a legend that was created in the so-called semi-shear method. The license plate can z. B. of a metal such as tinplate or aluminum or made of a plastic.

When Particularly suitable light sources have white LEDs proved at the time of the application already in large Quantity inexpensive with a light output of 3,000 and above Millicandela are available. At the stated light output, the use is from 5 to 40 Such light-emitting diodes advantageous, with 20 light-emitting diodes have proven to be optimal. To achieve the highest possible coupling efficiency of the light emitted by the white LEDs in the To achieve optical fibers, it has proven useful when the light guide on at least one longitudinal side of a light input surface forms, which forms a cylindrical lens. The light sources will be then along the longitudinal axis of the light input surface preferably evenly spaced. In this case, the shape of the Lichteinkoppelfläche as well the orientation of the light sources to the Lichtabstrahlcharakteristik the light sources are chosen to be adapted, in particular when using light emitting diodes, which is usually an asymmetrical one Have emission characteristic is advantageous.

Next White LEDs are a variety of other light sources for use in the erfindungemäßen Lighting device, the invention Shield assembly or the holder according to the invention suitable for a license plate. Exemplary here cold cathode lamps, incandescent or glow lamps, Surface Mounted LED, other semiconductor or polymer based light sources and electroluminescent elements, this list not afterwards.

In A preferred development are white LEDs used, whose emitter is poured directly into the light guide are. In this way, the trained at separately Light-emitting diodes otherwise inevitable Lichteinkoppelverluste be dramatically reduced.

In a preferred refinement, the illumination device of the shield arrangement has a light output device which is provided to selectively decouple the light guided in the light guide locally. In particular, this light output device can be designed so that the local coupling ratio increases as the intensity of the light guided in the light guide decreases. In general, in such a case, the Auskoppelgrad the light output device is substantially proportional to the Increase distance from the light input surface.

In A preferred embodiment is the light output device from one on at least one surface of the light guide formed roughness structure. This shows the roughness structure prefers structure sizes in the range between one and 50 microns, preferably between 4 and 40 microns. Structure sizes of up to 500 nm are also possible.

Appropriate Structure sizes can already be found in the Production of the light guide by injection molding from a highly transparent Plastic such as polycarbonate or PMMA are introduced, for example by an inner wall of the injection mold specifically with a corresponding Surface roughness is provided. Alternatively, a Surface of the light guide after its production with a roll are rolled off, the surface of which is a corresponding Surface roughness or may have z. B. by laser irradiation of the light guide light scattering impurities be introduced into the light guide. In the laser-assisted In particular, it is possible to generate impurities targeted the density profile of the impurities in the light guide to adjust, for. B. by the focus of the impurity-generating Laser radiation is placed in a suitable depth in the light guide.

Either the inner wall of a z. B. metallic injection mold as well the surface of a z. B. metallic roller can by means of an etching process with a corresponding surface roughness be provided, the special procedure the etching process, the generated surface structure, in particular determines the structure size.

alternative may have appropriate surface textures both in the injection mold as well as on the surface of the roller achieved by a mechanical surface treatment, for example, by sand or glass beads, the chemical Surface treatment is preferred. Will the surface texture produces the tools by means of chemical processes, so has the with the surface structure provided light guide in the Usually improved optical properties, in particular an improved Transparency, compared to such light guides, with Tools were processed by mechanical methods were treated.

In An alternative approach is the light guide with light scattering ends Particles doped, with both a homogeneous and an inhomogeneous Doping of the light guide is possible. The with light scattering Particles doped layer of the light guide then forms the inventive Light output. By suitable process management in the manufacture of the light guide, it is possible in particular an inhomogeneous concentration profile of the light-scattering particles be generated in the optical fiber such that on at least one surface of the light guide an increased concentration of light scattering Particle is set. Particularly preferred is the use organic particles as light-scattering particles, alternatively However, inorganic particles such as silica particles used become. It is known that the size of the light scattering Particles for their light-scattering properties, in particular responsible for the light scattering characteristic. Corresponding the particle size is preferably selected specifically such that the desired light scattering properties as possible slight negative influence on retroreflection and contrast be achieved. Suitable particle sizes are here in the range of 500 nanometers to about 50 microns, wherein a particle size in the range between a and 10 microns, especially in the context of organic Has proven particularly light scattering particles.

Especially It has proven itself, only one surface of the light guide the illumination device with a light output device to provide, which preferably at that surface the light guide is arranged on the to be illuminated Shield oriented side of the light guide is because so that the Contrast, d. H. the readability, the retroreflective mark is improved.

Further advantages can be realized if at least one surface of the optical waveguide of the illumination device has a reflection-reducing design, wherein for practical reasons a reflection-reducing configuration of that surface of the optical waveguide has been proven, which is oriented towards the shield to be illuminated. In particular, such a reflection-reducing configuration can be achieved by providing the reflection-reducing surface of the optical waveguide with structures which lie in the range of a few nanometers. Corresponding structures have a model in nature and are also referred to as "moth-eye structure." The production of such structures is known, for example, from the German Offenlegungsschrift DE 103 185 66 A1 which discloses a heat sealing process of an optical fiber surface. Furthermore, from the German patent application DE 100 20 877 A1 an injection molding process for producing a light guide with a corresponding reflection-reducing designed surface known. at de pre-published documents are incorporated by reference in their entirety into the disclosure of the present application.

In a further advantageous embodiment of the invention Shield assembly is the surface of the light guide, oriented away from the sign to be illuminated, increasing scratch resistance designed. For this purpose, from the prior art also a Many possible methods are known which are specific the material used for the light guide are suitable. Consists the light guide made of a polymeric material such as PMMA, so has an overlay of the polymer surface with proven a special scratch protection on a polymeric basis, such as in the field of automotive headlight production already state of the art in mass production. U. a. Here the company GE Bayer Silicone offers a special scratch-resistant seal sold under the product name SHC 5020. These Scratch-resistant seal is applied in liquid form to the to be sealed surface of the polymeric workpiece applied and subsequently cured. This kind of Scratch protection is an additional scratch protection disc vorzuziehen, since here the retroreflection of the plate by a lower number of optical air-plastic transitions less is reduced.

Of the Holder for a license plate according to the invention comprises a lighting device which is in common with a retroreflective shield held by the holder, in particular a license plate, an inventive Shield arrangement represents. The following are two embodiments for a light guide of the illumination device of the invention Shield assembly described in detail.

In A first embodiment of the light guide made of PMMA and doped with organic light scattering agents. As a suitable PMMA material has the under the product name 8 N Crystal clear from the company Röhm GmbH, Darmstadt, Germany offered material, especially proven. This can with under the designation 8 N DF 20 offered by the same manufacturer Material are mixed, which organic light scattering particles contains. A mixing ratio of 2% of the material 8 N DF 20 in relation to 98% of the material 8 N Crystal clear has been optimal with a thickness of the optical fiber of 2.5 mm proved. Such a light guide is particularly suitable for use with a standard identifier according to the applicable German licensing regulations, which is a retroreflection of about 60 candelas per lux and square meters. The on the described Made optical fiber has a transmission, the a total retroreflection of the invention Shield arrangement of about 40 candela per lux and square meters or allowed over it.

If, on the other hand, retroreflective signs are used which have a significantly higher retroreflection than the retroreflective markers currently permitted in Germany, the doping of the light guide can easily be increased. Examples of such signs are signs that are equipped with a retroreflective sheeting containing microprismatic elements, such as. B. from the DE 69904512 3M Corp., USA. Although the increased doping of the light guide with light-scattering particles reduces its linear transmission, which reduces the total retroreflection. This is usually completely unproblematic due to the extremely high retroreflective values of the microprismatic reflective films. Under certain circumstances, even a reduction in the very high retroreflection of these films may be absolutely necessary in order to make the use of a shield arrangement according to the invention for a license plate for the first time permissible.

in the Backing can by increasing the Auskoppelgrads however the illumination of the license plate can be improved, making it In particular, the number or light intensity can be possible to lower the light sources used, causing z. B. cost advantages can result.

Prefers However, this is also a retroreflection of at least 40 candela per lux and square meter. The light guide with the specified Material composition already has such Lichtauskoppeleigenschaften on that when using 20 LED SUW 30030 the company Oshino Lamps GmbH the illumination according to the invention amounting to at least 2.5 candela per square meter of Shield assembly according to the invention is achieved.

The optical properties of the illumination device are advantageously adjusted so that the contrast K between the retroreflective background and the black-colored legend of the indicator to be illuminated is given by the following equation: K = (imax - imine) / (imax + imine) does not fall below 1: 3, in particular not below 1:10 and preferably not below 1:15. For this purpose, attention must be paid to a not too greatly reduced transmission of the light guide of the illumination device, whereby a more reduced transmission is tolerable here also at a high retroreflection of the shield.

Out the embodiments discussed above clearly that the characteristics of the lighting device up the properties of the plate to be illuminated are matched can or must, which in turn also an inclusion of the properties of the retroreflective shield possible in the optimization process according to the invention is.

Further Benefits may arise when the light scattering Particles are not distributed homogeneously in the light guide, but a Concentration profile is set in which the particle concentration in the area of the surfaces of the light guide, at least on a surface of the light guide, clearly opposite the volume material is increased. Such an inhomogeneous Particle concentration can be achieved with suitable process control realize in the manufacture of the light guide, for example by overlaying a monolayer of light-scattering particles, which are arranged on a base, with a crystal-clear polymer material.

All in all should the transmission of the illumination device of the invention Shield arrangement together with the reflection losses when passing through the surfaces of the light guide of the lighting device at least 25%, but preferably at least 50% and in particular about 75%. Basically, the readability of the legend of the illuminated sign with increasing transmission of the illumination device, here in particular of the light guide, too, so that high transmission levels the optical fiber substrate are generally preferred.

In a second embodiment, the light output device of the shield assembly 100 formed by a roughness structure formed on the surface of the light guide. Such a roughness structure can be introduced into the surface of the light guide in a variety of ways, in particular by direct mechanical or chemical processing of the surface of the finished light guide. An example of this is the rolling or embossing of the optical waveguide surface with a heated roll, the roll itself being provided with a suitable surface structure. Such a surface structure whose dominant structure size is preferably in the range between 0.5 and 50 microns, for example, by means of mechanical processing of the roll surface such. B. generated by sandblasting. Improved optical properties of the rolled-out optical waveguide can be achieved if the surface structure of the roll is produced by a chemical treatment, for example by means of an etching process, the surface structures again being in the stated order of magnitude. However, an immediate chemical treatment of the optical waveguide surface, for example by means of an etching process, is also conceivable in order to produce surface structures in the stated order of magnitude.

Prefers does not make the structuring of the light guide surface homogeneously executed. Rather, the Auskoppelgrad the Light output device targeted locally adjusted so that total a homogeneous illumination of the held sign is achieved. The Auskoppelgrad can locally, for example, by variation of the dominant wavelength or structural depth of the roughness structure be set. Also, the roughness structure itself only introduced in certain areas of the optical fiber surface while other surface portions of the light guide left untreated.

Next the subsequent attachment of the training the Lichtauskoppeleinrichtung required roughness structures on at least one surface of the ready-made Fiber optic, it is also possible the roughness structure already in the production of the light guide in the light guide surface to mold. For this it is possible, for example, a Surface of one for the manufacture of optical fibers used injection mold specifically with a surface roughness to be provided, which is then molded into the light guide. Here too can provide the required surface texture through a mechanical or chemical treatment of the inner wall of the injection mold achieved be, in turn, a chemical treatment of the inner wall as advantageous for the optical properties, in particular the achievable transmittance of the generated in the injection mold Fiber optic has proven. Alternatively it is possible in insert the injection mold into a separately formed matrix, which has a suitable surface structuring and the in the manufacture of the light guide in its surface is molded.

• 1. Erzeugung eines Lichtleiters mit planen Oberflächen beispielsweise im Spritzgussverfahren aus einem transparenten polymeren Werkstoff,
• 2. Behandlung zumindest einer Oberfläche des fertig gestellten Lichtleiters zur Einbringung einer Rauhigkeitsstruktur mit Strukturgrößen, die im Bereich zwischen 500 Nanometern und 50 Mikrometern liegen, bevorzugt im Bereich zwischen 4 und 40 Mikrometer, wobei hierzu zumindest eine Oberfläche des Lichtleiters mechanisch oder chemisch behandelt wird.

A possible manufacturing method for a light guide for realizing a shield arrangement according to the invention can therefore comprise the following method steps:

• 1. Generation of a light guide with flat surfaces, for example by injection molding, of a transparent polymer material,
• 2. Treatment of at least one surface of the finished optical waveguide for introducing a roughness structure with feature sizes ranging between 500 nanometers and 50 micrometers, preferably in the range between 4 and 40 micrometers, for which purpose at least one surface of the optical waveguide is treated mechanically or chemically.

• 1. Bereitstellen einer Spritzgussform zur Herstellung eines Lichtleiters, welcher zumindest eine Oberfläche aufweist, die eine Rauhigkeitsstruktur umfasst, welche Strukturgrößen im Bereich zwischen 500 Nanometern und 50 Mikrometern, bevorzugt zwischen 4 Mikrometern und 40 Mikrometern aufweist, wobei zumindest eine Innenwandung der Spritzgussform eine komplementäre Rauhigkeitsstruktur mit entsprechenden Strukturgrößen aufweist, und
• 2. Herstellen des Lichtleiters im Spritzgussverfahren unter Verwendung der bereitgestellten Spritzgussform.

An alternative manufacturing process comprises the following process steps:

• 1. Providing an injection mold for producing a light guide, which has at least one surface comprising a roughness structure having feature sizes in the range between 500 nanometers and 50 microns, preferably between 4 microns and 40 microns, wherein at least one inner wall of the injection mold has a complementary roughness structure having corresponding feature sizes, and
• 2. Manufacture the optical fiber by injection molding using the provided injection mold.

Finally It should be noted that various procedures for targeted Combining outcoupling of light from the light guide with each other to let. So you can easily with light-scattering particles doped optical fibers additionally targeted on your surface be provided with a roughness structure. Also the targeted Generation of light-scattering defects in the light guide by means of Laser irradiation and other techniques not mentioned here, with where the coupling out of a light guide can be controlled, are basically suitable here and can with combined with the methods mentioned here. By combination These techniques can be adjusted to an optimum Luminance, contrast / readability and retroreflection, this being in the case of application of a license plate according to the country-specific regulations

Particular advantages arise when a lighting device according to the invention 20 or a shield assembly according to the invention 100 be used for illuminating a license plate without a mounted on the exterior of the motor vehicle holder for holding the retroreflective license plate is used. In this case, the illumination device or the shield arrangement is used in a holder for a license plate which is integrated into a component of a motor vehicle. It may be in this component of the vehicle z. B. act for a bumper, a boot lid or a hood. This allows an integration of the legally prescribed license plate number in the design of the motor vehicle, whereby an improved design freedom for the body of the vehicle and a total of an upgraded design can be realized. In addition, the anti-theft of the license plate can be improved because the integrated into the component of the car holder can be readily configured so that the license plate is only accessible from the vehicle interior.

• a. die durch die Ausleuchtung des retroreflektierenden Schilds (2) erzielte Abstrahlung der Schildanordnung (100) mindestens 2 Candela pro Quadratmeter beträgt, und
• b. die Retroreflektivität des retroreflektierenden Schilds (2) durch die Beleuchtungseinrichtung (20) um maximal 60%, bevorzugt um nicht mehr als 30% reduziert wird.

Schildanordnung (100) bestehend aus einem retroreflektierenden Schild (2) mit einer Legende und einer Beleuchtungseinrichtung (20), wobei die Beleuchtungseinrichtung (20) einen flächenhaft ausgedehnten Lichtleiter (80) umfasst, der vorderseitig des auszuleuchtenden retroreflektierenden Schilds (2) angeordnet und dazu vorgesehen ist, das retroreflektierende Schild (2) durch Auskopplung von im Lichtleiter (80) geführtem Licht homogen auszuleuchten, dadurch gekennzeichnet, dass die Beleuchtungseinrichtung (20) so ausgestaltet ist, dass

• c. die durch die Ausleuchtung des retroreflektierenden Schilds (2) erzielte Abstrahlung der Schildanordnung (100) mindestens 2 Candela pro Quadratmeter beträgt, und
• d. die Retroreflektivität der Schildanordnung (100) mindestens 20 Candela pro Lux und Quadratmeter beträgt.

Schildanordnung (100) gemäß Anspruch 2, dadurch gekennzeichnet, dass die Anforderungen der im Anmeldezeitpunkt geltenden ECE-Vorschrift ECE-4 zu Kfz-Kennzeichen zumindest in Bezug auf Ausleuchtung und Lesbarkeit des Kennzeichens erfüllt werden.
Schildanordnung (100) gemäß Anspruch 2, dadurch gekennzeichnet, dass die Beleuchtungseinrichtung (20) eine oder mehrere weiße Lichtquellen (22) umfasst, die längs einer vom Lichtleiter (20) ausgebildeten Lichteinkoppelfläche (84) angeordnet sind.
Schildanordnung (100) gemäß Anspruch 3, dadurch gekennzeichnet, dass die weißen Lichtquellen (22) von weißen Leuchtdioden gebildet werden.
Schildanordnung (100) gemäß Anspruch 3, dadurch gekennzeichnet, dass die Lichtquellen (22) in den Lichtleiter (20) eingegossen sind.
Schildanordnung (100) gemäß Anspruch 2, dadurch gekennzeichnet, dass die Beleuchtungseinrichtung (20) eine Lichtauskoppeleinrichtung aufweist, die dazu vorgesehen ist, im Lichtleiter (80) geführtes Licht gezielt lokal auszukoppeln.
Schildanordnung (100) gemäß Anspruch 6, dadurch gekennzeichnet, dass die Lichtauskoppeleinrichtung von einer auf einer Oberfläche des Lichtleiters (80) ausgebildeten Rauhigkeitsstruktur gebildet wird.
Schildanordnung (100) gemäß Anspruch 6, dadurch gekennzeichnet, dass die Rauhigkeitsstruktur Strukturgrößen im Bereich zwischen 0,5 und 50 Mikrometern aufweist.
Schildanordnung (100) gemäß Anspruch 7, dadurch gekennzeichnet, dass die Rauhigkeitsstruktur bei der Herstellung des Lichtleiters (80) im Spritzgussverfahren durch Verwendung einer Spritzgussform, die eine Innenoberfläche mit kontrollierter Oberflächenrauhigkeit aufweist, erzeugt wird.
Schildanordnung (100) gemäß Anspruch 7, dadurch gekennzeichnet, dass die Rauhigkeitsstruktur bei der Herstellung des Lichtleiters (80) durch Abwalzen einer Oberfläche des Lichtleiters (80) mit einer Walze, die eine Oberfläche mit kontrollierter Oberflächenrauhigkeit aufweist, erzeugt wird.
Schildanordnung (100) gemäß Anspruch 9 oder 10, dadurch gekennzeichnet, dass die Oberflächenrauhigkeit der Innenoberfläche der Spritzgussform bzw. der Walze mittels eines Ätzprozesses erzeugt wird.
Schildanordnung (100) gemäß Anspruch 6, dadurch gekennzeichnet, dass die Lichtauskoppeleinrichtung von einer im oder auf dem Lichtleiter (80) ausgebildeten Lichtstreuungsschicht gebildet wird, die mit lichtstreuenden Partikeln dotiert ist.
Schildanordnung (100) gemäß Anspruch 12, dadurch gekennzeichnet, dass es sich bei den lichtstreuenden Partikeln um organische Partikel handelt.
Schildanordnung (100) gemäß Anspruch 6, dadurch gekennzeichnet, dass die Lichtauskoppeleinrichtung an der zum auszuleuchtenden Schild (2) hin orientierten Oberfläche des Lichtleiters (80) angeordnet ist.
Schildanordnung (100) gemäß Anspruch 6, dadurch gekennzeichnet, dass die Lichtauskoppeleinrichtung zur Erzielung einer homogenen Ausleuchtung des auszuleuchtenden Schilds (2) eine lokal variierende Auskoppelstärke aufweist.
Schildanordnung (100) gemäß Anspruch 2, dadurch gekennzeichnet, dass die zum auszuleuchtenden Schild (2) hin orientierte Oberfläche des Lichtleiters (80) und/oder die vom auszuleuchtenden Schild (2) weg orientierte Oberfläche des Lichtleiters (80) Reflexionsmindernd ausgestaltet ist.
Schildanordnung (100) gemäß Anspruch 16, dadurch gekennzeichnet, dass für die Reflexionsmindernde Ausgestaltung der Oberfläche des Lichtleiters (80) Strukturen mit Abmessungen im Bereich einiger Nanometer vorgesehen sind.
Schildanordnung (100) gemäß Anspruch 2, dadurch gekennzeichnet, dass die vom auszuleuchtenden Schild (2) weg orientierte Oberfläche des Lichtleiters (80) Kratzfestigkeitserhöhend ausgestaltet ist.The following embodiments of the lighting device are considered by the applicant to be fundamentally advantageous:
Lighting device ( 20 ) for a retroreflective shield ( 2 ) with a legend, with a planar extended light guide ( 80 ) intended to be located on the front side of the retroreflective shield to be illuminated ( 2 ) to be placed around the retroreflective shield ( 2 ) by decoupling in the optical fiber ( 80 ) homogeneously illuminate guided light, characterized in that

• a. caused by the illumination of the retroreflective shield ( 2 ) radiation of the shield arrangement ( 100 ) is at least 2 candela per square meter, and
• b. the retroreflectivity of the retroreflective shield ( 2 ) by the illumination device ( 20 ) is reduced by a maximum of 60%, preferably by not more than 30%.

Shield assembly ( 100 ) consisting of a retroreflective shield ( 2 ) with a legend and a lighting device ( 20 ), wherein the illumination device ( 20 ) a planar extended optical fiber ( 80 ), the front side of the retroreflective shield to be illuminated ( 2 ) and is provided to the retroreflective shield ( 2 ) by decoupling in the optical fiber ( 80 ) led light homogeneously, characterized in that the illumination device ( 20 ) is designed so that

• c. caused by the illumination of the retroreflective shield ( 2 ) radiation of the shield arrangement ( 100 ) is at least 2 candela per square meter, and
• d. the retroreflectivity of the shield assembly ( 100 ) is at least 20 candela per lux and square meter.

Shield assembly ( 100 ) according to claim 2, characterized in that the requirements of applicable at the time of registration ECE Regulation ECE-4 to license plates are met at least in terms of illumination and readability of the plate.
Shield assembly ( 100 ) according to claim 2, characterized in that the illumination device ( 20 ) one or more white light sources ( 22 ) along one of the optical fibers ( 20 ) formed Lichteinkoppelfläche ( 84 ) are arranged.
Shield assembly ( 100 ) according to claim 3, characterized in that the white light sources ( 22 ) are formed by white LEDs.
Shield assembly ( 100 ) according to claim 3, characterized in that the light sources ( 22 ) in the light guide ( 20 ) are poured.
Shield assembly ( 100 ) according to claim 2, characterized in that the illumination device ( 20 ) has a light output device which is provided in the light guide ( 80 ) guided light out selectively locally.
Shield assembly ( 100 ) according to claim 6, characterized in that the light output device of a on a surface of the light guide ( 80 ) formed roughness structure is formed.
Shield assembly ( 100 ) according to claim 6, characterized in that the roughness structure has feature sizes in the range between 0.5 and 50 microns.
Shield assembly ( 100 ) according to claim 7, characterized in that the roughness structure in the manufacture of the light guide ( 80 ) is produced by injection molding using an injection mold having an inner surface with controlled surface roughness.
Shield assembly ( 100 ) according to claim 7, characterized in that the roughness structure in the manufacture of the light guide ( 80 ) by rolling a surface of the light guide ( 80 ) is produced with a roller having a surface with controlled surface roughness.
Shield assembly ( 100 ) according to claim 9 or 10, characterized in that the surface roughness of the inner surface of the injection mold or the roller is produced by means of an etching process.
Shield assembly ( 100 ) according to claim 6, characterized in that the light output device of a in or on the light guide ( 80 ) formed light scattering layer is doped with light-scattering particles.
Shield assembly ( 100 ) according to claim 12, characterized in that the light-scattering particles are organic particles.
Shield assembly ( 100 ) according to claim 6, characterized in that the light output device on the plate to be illuminated ( 2 ) oriented surface of the light guide ( 80 ) is arranged.
Shield assembly ( 100 ) according to claim 6, characterized in that the light output device for achieving a homogeneous illumination of the sign to be illuminated ( 2 ) has a locally varying Auskoppelstärke.
Shield assembly ( 100 ) according to claim 2, characterized in that the sign to be illuminated ( 2 ) oriented surface of the light guide ( 80 ) and / or the sign to be illuminated ( 2 ) oriented surface of the light guide ( 80 ) Is designed reflection-reducing.
Shield assembly ( 100 ) according to claim 16, characterized in that for the reflection-reducing configuration of the surface of the light guide ( 80 ) Structures are provided with dimensions in the range of a few nanometers.
Shield assembly ( 100 ) according to claim 2, characterized in that the sign to be illuminated ( 2 ) oriented surface of the light guide ( 80 ) Is designed to increase scratch resistance.

Further advantageous (complementary or alternative) embodiments the inventive method and the inventive Light guide assembly, the mounting device according to the invention, the illuminable retroreflective invention License plate plate arrangement and the invention Motor vehicle with integrated illuminated holding device for a retroreflective license plate will result the subclaims as well as those discussed below Embodiments, with reference to the drawing be explained. In this show:

1 2 is a perspective partial sectional view of a mounting device according to the invention for fastening a retroreflective license plate on a motor vehicle;

2 an enlarged view of the section through the mounting device 1 .

3 a partial sectional view through the lower edge of the mounting device 1 .

4 a partial sectional view through the upper edge of the mounting device 1 .

5 an enlarged partial view of the light guide of the arrangement 1 , placed on the license plate to be illuminated,

6 a perspective view of the mounting plate of the arrangement 1 in top view, or top

7 a scanning electron micrograph (SEM) of the surface of the optical waveguide of a first optical waveguide arrangement according to the invention in a low magnification,

8th the SEM recording off 7 in a higher magnification,

9 a plan view of a schematically illustrated light guide of a second optical fiber arrangement according to the invention,

10 a plan view of a schematically illustrated optical fiber of a third optical fiber arrangement according to the invention,

11 a section through the schematically illustrated optical fiber of a fourth optical fiber arrangement according to the invention,

12 a section through the schematically illustrated optical fiber of a fifth optical fiber array according to the invention, and

13a F the sequence of a method for producing a die for an injection mold for producing a light guide for an inventively designed light guide assembly.

1 shows a partial sectional view through a device according to the invention Montagevor 1 for a retroreflective license plate 2 with a two-dimensional shield plate in perspective view.

The mounting device 1 includes a holder 10 , which is designed to the license plate 2 to keep. The holder 10 is further adapted to be attached to a motor vehicle (not shown), such that the holder 10 held retroreflective license plate 2 is determined mechanically on the vehicle.

In the embodiment shown, the holder comprises 10 a bottom mounting plate 30 , in the 6 is shown and can be made for example by injection molding of a high impact thermoplastic such as ABS. With the rear mounting plate 30 , which is intended to be mounted on a motor vehicle and whose structure will be discussed further below, is a license plate unit on the upper side 40 connected, the captive with the mounting plate 30 is connected, with the connection between the mounting plate 30 and the license plate unit 40 can be solved without damage by means of tools.

The holder 10 the mounting device 1 thus consists of the mounting plate 30 and the license plate unit 40 , Inside the license plate unit 40 , which forms a closed housing, is a license plate 2 supported.

Furthermore, the mounting device comprises 1 an optical fiber arrangement according to the invention 5 , which will be discussed in more detail below. The light guide 80 the light guide assembly 5 is with the retroreflective license plate 2 front side of the areally expanded shield plate of the retroreflective license plate 2 is arranged. In this case, the light guide arrangement 5 completely within the closed housing of the license plate unit 40 arranged.

This case is above the salaried license plate 2 from the upper side arranged areally extended light guide 80 the light guide unit 5 covered, which by gluing or welding to the front panel 56 that part of a frame 50 the license plate unit 40 is connected. The front panel 56 also consists of an impact-resistant thermoplastic such as ABS and can be made for example by injection molding. The light guide 80 preferably consists of a transparent impact-resistant plastic. Preference is given here PMMA is used due to the high transparency and high mechanical strength. However, it is also conceivable to use other transparent plastics such as polycarbonate or polyethylene.

In addition, the front light passage surface 81 of the light guide 80 by applying a Hard and possibly also anti-reflective thin layer be hard-coated, whereby the scratch resistance of the light guide 80 increased while its reflectivity can be reduced, which significantly increases the readability of the license plate legend of the underlying license plate.

Furthermore, in the front panel 56 of the frame 50 mounting holes 44 provided, which allow an introduction of tools and in this way a separation of back mounting plate 30 and front license plate unit 40 allow.

The use of a mounting device 1 , their holders 10 as a license plate unit 40 is formed with a closed housing, which with a provided for mounting on the vehicle mounting plate 30 is connectable, is optional and not necessary for the realization of the advantages of the invention. Also, the use of a compensation of the front light transmission surface 81 of the light guide 80 is optional.

The light guide arrangement 5 the illustrated mounting device 1 forms together with the in the license plate unit 40 arranged retroreflective license plate 2 an illuminable license plate assembly according to the invention 100 out.

2 now shows enlarged a section of the 1 apparent section through the mounting device according to the invention 1 from which their construction is more apparent. The holder 10 includes the rear mounting plate 30 , which captive but detachable with the upper side arranged license plate unit 40 connected is.

The license plate unit 40 forms a closed housing, in which a lighting device 20 as well as the license plate to be kept or illuminated 2 is arranged. In the to be kept license plate 2 it is preferably a license plate with metal plate, in particular with embossed metallic board, in which the legend is introduced in the form of raised embossed numbers. The lighting device 20 includes a plurality of light sources 22 , which from a common light source carrier 26 be worn and arranged evenly spaced. At the light sources 22 These are preferably white light LEDs (LED) of the SMD (surface mounted device) type, which operate with a low operating voltage and have a high optical output power. These are currently available from a number of suppliers and have the advantage of a homogeneous radiation characteristic with a long service life. The high efficiency of LED also leads to only a small heat development.

The LED is preferably white high-power LED, which have a light output of 1000 mcd and above. The company Oshino Lamps GmbH, Nuremberg, Germany, offers under the product name SUW 30030 white high-performance LED, which have a light output of typ. 4000 mcd at a beam angle of 30 °. The use of up to 20 LEDs of the type mentioned leads in connection with the holder 10 or the mounting device 100 of the illustrated embodiment to good results. If LEDs of the SMD type are used, the use of LEDs, which has been proven by Alder Deutschland GmbH, Talstr. 55, 71522 Backnang be sold under the product name AS-1311 WCA2-C2Z.

The majority of light sources 22 the lighting device 20 is in a long side of the license plate unit 40 arranged, wherein the beam direction of the individual light sources 22 with the level of the license plate 2 coincides.

The light sources 22 are supplied via a common supply line with electrical energy, wherein the supply line, not shown here via a sealed bore from the license plate unit 40 is led out.

For uniform illumination of the held license plate 2 is the top of the license plate 2 a planar extended light guide 80 arranged, which part of a light guide arrangement according to the invention 5 is. Here is the light guide 80 through the embossed raised edge of the license plate 2 spaced from the legend of the license plate 2 arranged. In this light guide 80 which is preferably made of a transparent plastic such as polycarbonate or PMMA, that of the light sources 22 emitted light in a suitable manner coupled. This will be discussed in more detail below. In the light guide 80 becomes the coupled light of the light sources 22 guided by total internal reflection.

Here is the (surface) nature of the light guide 80 in the area of its rear light passage area 83 designed so that at every internal total reflection through targeted into the light guide 80 introduced light extraction structures 90 a small percentage of the incident radiation is coupled out and directed to the underlying license plate so that it is illuminated. On these light extraction structures 90 , which according to the invention can be characterized in that one of the running direction L of the light guide 80 guided light dependent Lichtauskoppelgrad, will also be discussed in more detail below. First, it should be mentioned that by targeted structuring of the surface 83 of the light guide 80 in the light sources 22 adjacent areas in the area of light sources 22 greatly increased intensity in the light guide 80 can be compensated by the decoupling is significantly reduced locally there. In principle, however, it is also possible to dispense with an inhomogeneous design of the decoupling degree and to set the decoupling degree essentially homogeneous over the entire surface of the optical waveguide, as long as the applicable regulations of ECE-4 with regard to the homogeneity of the illumination of the license plate are met.

The housing of the license plate unit 40 is formed in the embodiment shown of several components. A frame 50 which is a front panel 56 and a back holder 58 comprises, which are manufactured as separate parts and in the context of the preparation of the holder according to the invention 1 Undetachably connected to each other, for example by means of welding, have a front opening, in which the areal extended optical fiber 80 is used. The light guide 80 is, as already mentioned, insoluble with the front panel 56 of the frame 50 connected, for example by means of bonding. In the embodiment shown, the front panel are 56 as well as the back holder 58 each made by deep drawing or injection molding and each consists of an impact-resistant thermoplastic such as ABS.

The frame 50 the license plate unit 40 has an access opening on the back 52 on, extending over the entire rear surface of the frame 50 extends and whose dimensions are such that through the access opening 52 the retroreflective license plate to be held 2 in the frame 50 can be inserted. If the license plate is inserted, it comes into contact with pressure surfaces 59 which in the back holder 58 are formed, as well as with the rear light passage surface 83 of the light guide 80 , which forms a mechanical support.

After the license plate 2 in the frame 50 is inserted, the license plate unit 40 by means of a lid 60 hermetically sealed. For this purpose, the rear holder 58 a circumferential sealing strip 54 on. At the same time the lid forms 60 a circumferential receiving groove 62 made, which in their shape complementary to the circumferential sealing strip 54 is trained. The material of the lid 60 now has one opposite the material of the frame 50 increased elasticity, the dimensions of the lid 60 , here in particular the circumferential receiving groove 62 , so dimensioned that the lid 60 with its circumferential receiving groove 62 on the sealing strip 54 the back holder 58 can be raised. Here learns the lid 60 a certain elastic elongation, causing the lid 60 on the circumferential sealing strip 54 is determined. As material for the lid 60 thermoplasti cal polyurethanes have proven, for example, the marketed by Bayer MaterialScience AG under the brand Desmopan ^® thermoplastic aliphatic polyurethane. This has an increased elasticity compared to ABS, so that the lid 60 in the manner known by plastic boxes from the food industry on the sealing strip 54 of the frame 50 can be raised, with a sealing seat of the sealing strip 54 in the receiving groove 62 results. This will do so by the license plate unit 40 trained housing 10 through the lid 60 sealed sealed.

3 now shows the off 2 apparent right edge of the license plate unit 40 enlarged again. Clearly visible is the two-part structure of the frame 50 which consists of a front panel 56 and the back holder 58 is formed. The front panel 56 forms a recess into which the light guide 80 is inserted sealed.

The back holder 58 forms a joint with the front panel 56 a receptacle for the lighting device 20 with its plurality of light sources 22 and the light source carrier 26 out. Be the front panel 56 and the back holder 58 joined together, so hereby the light source carrier 56 and with it the light sources 26 fixed.

Furthermore, the light guide forms 80 on its longitudinal sides peg-shaped fastening arms 86 out, that out 5 can be seen in detail. These attachment arms 86 are through through holes in the light source carrier 86 passed through and permanently connected by thermal caulking with this. To Combine the frame 50 becomes the light guide 80 therefore in a first step captive with the light source carrier 26 the lighting device 20 connected on the the majority of light sources 22 is arranged. Then this prefabricated optical fiber assembly 5 then in the front panel 56 used. Below is on the back of the front panel 56 the back holder 58 fitted and with the front panel 56 welded. As a result, the light guide arrangement 5 again in the frame 50 set, in particular captive connected to this.

How out 5 the light guide is visible 80 the edge of a plane coupling surface 84 from, in which the light sources formed by the SMD LEDs in the embodiment shown 22 emitted light is coupled. For this purpose, the flat light emission surfaces of the SMD LEDs during assembly of the light guide 80 at the illumination device in mechanical contact with the coupling surface 84 brought. An optical coupling of the LEDs to the light guide z. B. by filling the remaining air gap between the light emitting surfaces of the SMD LEDs and the light input surface 84 with an adhesive whose refractive index is on the refractive index of the light guide 80 As well as the SMD LEDs is tuned, may be advantageous, but is not mandatory.

Furthermore, the geometry of the frame 50 , in particular the light guide 80 , so dimensioned that when assembled frame 50 an air gap between the front screen 70 and the light guide 80 remains, so that a decoupling in the light guide 80 guided light by a coupling in the protective screen 70 avoided if possible. By having a separate protective screen 70 is provided, which itself not as a light guide of the lighting device 20 An undesirable increased coupling of light from the light guide may act 80 due to mechanical damage of the front light exit surface of the holder according to the invention 1 be largely avoided.

Is the license plate to be kept 2 at the back of the license plate unit 40 by the in the license plate unit 40 trained access opening 52 inserted, which in the embodiment shown practically over the entire rear surface of the rear holder 58 extends, so does the access opening 52 of the frame 50 by means of a lid 60 hermetically sealed. For this purpose, the back holder forms 58 as already mentioned a circumferential sealing strip 54 on. Furthermore, the lid forms 60 a circumferential receiving groove 62 out. The shape of the sealing strip 54 and the receiving groove 62 are adapted to each other so that a positive connection between the sealing strip 54 and receiving groove 62 results when the lid 60 on the back of the frame 50 is put on.

Like from the 3 and 4 it can be seen forms a lid described in more detail below 60 on both sides integrally formed Andruckhöcker 64 out. These pressure humps 64 Press the inserted license plate 2 with its raised embossed peripheral edge against the light guide arranged on the front side 80 , so that unwanted movements of the license plate in the holder 1 , which may be source of noise, is avoided. Likewise, these humps stretch 64 the complete license plate unit 40 against the rear mounting plate 30 in front.

After assembling the components described above, the license plate unit is 40 the mounting device according to the invention 1 operational. The completed license plate unit 40 with inserted license plate 2 can now with a (for example by means of screwing firmly connected to a motor vehicle) mounting plate 30 be connected that out 6 is apparent.

For such a connection with the car are in the mounting plate 30 a variety of mounting breakthroughs 34 provided in the manufacture of the mounting plate 30 have been formed with. Manufacturing technology, it is advantageous if these mounting apertures 34 not yet completely broken during production.

For fastening the license plate unit to the mounting plate 30 is in the embodiment shown on the mounting plate 30 a circumferential edge 32 educated. Behind this engages in the mounting of the frame to the mounting plate 30 one on the front panel 56 of the frame 50 trained locking projection 57 a (cf. 4 ). On the opposite side is the front panel 56 of the frame 50 as inward springy noses 33 which, when plugging the license plate unit 40 on the mounting plate 30 in engagement with the peripheral edge 32 reach and snap into place (cf. 3 ). In this way, a firm connection between the license plate unit 40 and the mounting plate 30 realized.

To solve this mechanical connection are in the front panel 56 a plurality of Dismantling openings 44 trained, for example, from 1 can be seen. Through these disassembly openings 44 a suitable tool can be introduced, with the help of the resilient noses 33 from the surrounding edge 32 can be solved so that the license plate unit 40 can be pulled off to the front.

4 now shows the in 2 left longitudinal side of the mounting device according to the invention 1 in an enlarged view in section. In the embodiment shown is on this side of the license plate unit 40 no further lighting device 20 intended. This page is located at the top of the practical use of the mounting device. On this page is the end of the light guide 80 formed as a retroreflector by two at the critical angle of total reflection relative to the light path in the light guide 80 the arranged reflection surfaces 87 are formed. That in the light guide 80 propagating light is when hitting these two end reflection surfaces 87 deflected by 180 °, allowing in this way the efficiency of the lighting device 20 is increased.

From the 3 and 4 is further seen that along the outer edge of the lid 60 adjacent to the circumferential receiving groove 62 a production recess 66 is incorporated. This manufacturing recess 66 simplifies the manufacture of the lid 60 by injection molding and increases the flexibility of the receiving groove 62 ,

9 schematically shows a bottom plan view of the rear light passage surface 83 of the transparent light guide 80 a light guide arrangement according to the invention 5 , As already explained above, a plurality of light sources designed as light-emitting diodes are on one longitudinal side of the light guide 22 arranged, the light in a suitable manner in the light guide 80 is coupled so that it is guided due to total internal reflection in the light guide and along the direction L, the in 7 indicated by arrows, propagates. The optical fiber has dimensions typically in the range of 500 mm in length, 150 mm in width and in a thickness of 2 to 5 mm.

In the area of the rear light passage surface 83 is now a variety of Lichtauskoppelstrukturen 90 arranged in the embodiment according to 8th are arranged irregularly. In contrast, shows 10 an otherwise identical to another embodiment in which the light extraction structure 90 regularly on the rear light passage surface 83 of the light guide 80 are arranged. In both embodiments, the light extraction structures 90 as raised or recessed structures in the rear light passage area 83 educated. Will the light guide 80 produced by an injection molding process, so the Lichtauskoppelstrukturen 90 advantageous already in the manufacture of the light guide 80 be formed integrally with this.

Alternatively, it is possible, the light output structures shown by rolling the rear light passage surface 83 of the light guide 80 to produce after the light guide 80 was produced for example by injection molding. Here, the light guide surface 81 rolled off with a heated roller and thereby stamped, wherein the roller itself is provided with a suitable surface structure itself. Such a surface structure whose dominant structure size is preferably in the range between 0.5 and 50 microns, for example, by means of mechanical processing of the roll surface such. B. be generated by sandblasting in a preferred direction. Improved optical properties of the rolled optical fiber 80 can be achieved when the surface structure of the roller is produced by a chemical treatment, for example by means of an etching process, wherein the surface structures are again in the specified order of magnitude. However, it is also conceivable direct chemical treatment of the optical fiber surface 81 For example, by means of an etching process to produce surface structures of the order of magnitude mentioned.

In a modification of the aforementioned method, the light guide 80 produced by extrusion. The surface 81 the still warm light guide 80 is subsequently rolled off with a possibly heated roller, as described above.

Finally, it has been found that corresponding structures by means of a polishing process of an initially planar transparent light guide 80 can be generated, which in turn may have been produced for example by injection molding. For a light guide made of PMMA 80 very good results could be achieved by the rear light passage surface 83 of the light guide 80 over a period of a few seconds to about 10 minutes less in a preferred direction, which transverse to the direction L of the light in the optical fiber and thus generally parallel to the longitudinal axis of the optical fiber shown 80 was oriented. Was used for this purpose z. B. a polishing paste for transparent plastic top which is marketed under the name Displex ^® from EVI GmbH, 82061 Neuried, Germany faces.

7 shows a scanning electron micrograph of the surface of a PMMA light guide 80 , which was treated in the aforementioned manner, wherein the recording was obtained by means of secondary electrons. Clearly visible are the depressions in the surface of the optical waveguide that appear linear in the selected magnification 80 which extend in a preferred direction. In this preferred direction, they have dimensions that can be well above 1 mm.

Out 8th which made an enlarged section 7 1, it can be seen that the typical structure width b of the generated line-like structures is in the range of 10 microns. Typical structure heights h are in the range of one micrometer. The density of the generated linear structures in the direction L of the light in the light guide is about 50 lines / millimeter. It could be determined experimentally that the density of the line-like structures in the running direction L (ie perpendicular to the longitudinal axis of the structures) is preferably between 1 and 1000 lines / millimeter, with an interval in the range between 10 and 100 lines / millimeter being preferred.

From the scanning electron micrographs of the surface of the prepared by polishing light guide 80 according to the 7 and 8th the following roughness parameters of the analyzed surface can be determined: Average roughness sRa about 0.05 microns, roughness SRZ about 1.25 microns, Max. roughness SR max about 2.25 microns, peak height SRP about 0.55 microns, cried distance SRV about 1.65 microns, roughness SRT about 2.25 microns

The roughness characteristic values mentioned here are to be understood as examples and do not necessarily provide optimized values with regard to the properties of the light guide arrangement to be realized according to the invention 5 represents.

11 shows an enlarged section through the light guide 80 a light guide arrangement according to the invention 5 , wherein the cutting plane is oriented transversely to the longitudinal axis of the light guide, ie in the running direction L of the light in the light guide 80 extends. That is in the light guide 80 Light propagating along the direction of travel is due to internal total reflection in the light guide 80 guided. If a light beam strikes one in the rear light passage surface 83 introduced light extraction structure 90 , so locally the angle condition for the total internal reflection is not met, but the light beam via the Lichtauskoppelstruktur 90 on the back light passage surface 83 exit from the light guide. He then arrives at the retroreflective license plate 2 , is retroreflected by this and passes through the light guide 80 the light guide assembly and out of the front light passage surface 81 off, so that the license plate legend of the license plate appears illuminated for a viewer.

11 also shows the embodiment of the invention to be provided Auskoppelstrukturen the third embodiment in section. These have a substantially three-sided cross section and extend transversely to the running direction L of the light in the light guide 80 , ie in the direction of the longitudinal axis of the license plate 2 , Typical feature sizes are a base width b in the range 1 to 10 micrometers, a feature height h in the range of 0.1 to 5 micrometers, and a typical feature length l (see FIG. 8th and 9 ), which may range from 50 microns to a few millimeters. The typical structure distance d in the running direction L of the light in the light guide 80 is 5 to 50 microns, preferably 10 to 20 microns.

12 shows an analogous section through an optical fiber 80 a further optical fiber arrangement according to the invention 5 Here, the lichtauskop pelnden structures 90 are formed as block-like structures with rounded top surface. The data for structure sizes and structure densities essentially correspond to those of the exemplary embodiment 9 ,

The in the 11 and 12 as sublated decoupling structures 90 Alternatively, they can be used as equivalently shaped depressions in the light guide 80 be executed.

The light extraction structures according to 9 and 11 respectively. 10 and 12 can be manufactured by direct polishing of the front light transmission surface 81 of the light guide 80 as already mentioned. However, they can also be formed directly in a production of the light guide from a transparent plastic such as PMMA in an injection molding process. For this purpose, the corresponding negative structures are introduced into the injection mold and the rear light passage surface 83 of the light guide 80 molded by the structured injection mold. For this purpose, for example, a suitably structured insert can be inserted into the injection mold, which is provided by a positive with the desired structuring z. B. was galvanically molded. In this way, for example, the structure produced by means of the direct polishing of the optical waveguide surface can be multiplied by injection molding.

Corresponding positive forms can also be produced by photolithographic processes which are known per se from the prior art. In this context, z. B. on the US 2005/036083 A1 the disclosure of which is incorporated by reference in its entirety into the disclosure content of the present application.

For the preparation of structures according to 12 can z. B. the so-called UV lithography used, the process flow on the basis of 13a to f is explained in more detail. UV lithography means that microfine structures are produced by the shadow of a mask on a photosensitive resist layer (the so-called resist). Mercury vapor lamps usually serve as a radiation source. The microstructured mask is located in the shadow projection either directly on the resist or has a small distance to this. As an alternative, systems are used for the projection exposure, which reduce the size of the image by means of an imaging system. After irradiation, a wet-chemical development process takes place. The result is a cured, microstructured lacquer layer. Subsequently, a thermal method for smoothing the structures developed by UV lithography can be applied. In this case, rounding is achieved via the set temperature and contact time, which depend on the material properties and due to the surface tension. Hereby hemispherical cylinders can be produced which represent an example of the block-like structures with rounded top surface according to claim 9.

For example By means of electroforming is then produced in the UV lithography Structure "developed." The electroforming is to an engraving process, which is the galvanic process technology served. From the direct impression of templates can Duplicates are won, which are characterized by a very design-faithful Mark the reproduction of the original. It will be an arbitrary strength Nickel layer galvanized on a negative mold. This layer is separated from the mold, and you get a positive, that accurately reproduces all the details of the shape. So z. B. a tool insert for an injection molding tool Figure the required structures are produced.

Particular advantages arise when a lighting device according to the invention 20 or a shield assembly according to the invention 100 be used for illuminating a license plate without a mounted on the exterior of the motor vehicle holder for holding the retroreflective license plate is used. In this case, the lighting device 20 or the shield arrangement 100 used in a built-in a component of a motor vehicle holder for a license plate. It may be in this component of the vehicle z. B. act for a bumper, a boot lid or a hood. This allows an integration of the legally prescribed license plate number in the design of the motor vehicle, whereby an improved design freedom for the body of the vehicle and a total of an upgraded design can be realized. In addition, the anti-theft of the license plate can be improved because the integrated into the component of the car holder can be readily configured so that the license plate is only accessible from the vehicle interior.

The invention further relates to the use of a light guide 80 or a light guide arrangement 5 with the features according to claim 1 for illuminating a retroreflective shield 2 in general, in particular a license plate.

1

mounter for license plate

2

Car license plate

5

Optical fiber arrangement

10

holder (forms housing)

20

lighting device

22

light source

26

Light source carrier

28

guide rail

30

mounting plate

32

surrounding edge

34

Mounting breakthrough

40

License plate unit

44

Dismantling opening

50

frame

52

access opening

54

sealing strip

56

front cover

57

locking projection

58

back holder

59

pressure surface

60

cover

62

receiving groove

64

Andruckhöcker

66

Fertigungsausnehmung

80

optical fiber

81

front Light-transmitting surface

83

rear Light-transmitting surface

84

coupling surface

86

Mounting Arm

87

reflecting surface

90

Lichtauskoppelstrukturen

100

shield arrangement

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 2004062139 A [0002]
• - DE 10258465 A1 [0002, 0026]
• - DE 102005035232 [0020]
• - DE 10318566 A1 [0049]
• - DE 10020877 A1 [0049]
• - DE 69904512 [0053]
• US 2005/036083 A1 [0129]

Claims (20)

Light guide arrangement ( 5 ) for illuminating a vehicle-mounted retroreflective license plate ( 2 ), with a. a planarly extended transparent light guide ( 80 ) with a front light passage surface ( 81 ) and a rear light passage surface ( 83 ), and b. at least one light source ( 22 ), whose light in the light guide ( 80 i. coupled, ii. in a running direction L in this guided and iii. for illuminating the behind the light guide arrangement ( 5 ) arranged retroreflective license plate ( 2 ) is decoupled from this, where c. the light guide ( 80 ) in the region of a light passage surface ( 83 ) arranged Lichtsauskoppelstrukturen ( 90 ), characterized in that d. the light extraction structures ( 90 ) one of the running direction L of the in the light guide ( 80 ) have guided light dependent Lichtauskoppelgrad. Light guide arrangement ( 5 ) according to claim 1, characterized in that the light extraction structures ( 90 ) transverse to the direction L have larger dimensions than in the direction L. Light guide arrangement ( 5 ) according to claim 2, characterized in that the dimensions of the light extraction structures ( 90 ) transverse to the direction L at least by a factor of 10, preferably by a factor of 100, particularly preferably by a factor of 1000 greater than the dimensions in the direction of L. Light guide arrangement ( 5 ) according to claim 1, characterized in that the running direction L when used according to the light guide arrangement ( 5 ) is oriented substantially perpendicular to the horizontal. Light guide arrangement ( 5 ) according to claim 1, characterized in that the areal extended optical fiber ( 80 ) consists of plastic. Light guide arrangement ( 5 ) according to claim 1, characterized in that the light extraction structures ( 90 ) integral with the light guide ( 80 ) are formed geometric structures. Light guide arrangement ( 5 ) according to claim 6, characterized in that the light extraction structures ( 90 ) as raised or recessed structures in a light passage surface ( 83 ) are formed. Light guide arrangement ( 5 ) according to claim 7, characterized in that the light extraction structures ( 90 ) are formed as structures having a substantially three-sided cross-section. Light guide arrangement ( 5 ) according to claim 7, characterized in that the light extraction structures ( 90 ) are formed as block-like structures with rounded top surface. Light guide arrangement ( 5 ) according to claim 5 and 6, characterized in that a. the light guide ( 80 ) is made by injection molding, and b. the light extraction structures ( 90 ) during injection molding of the light guide into one of the light passage surfaces ( 83 ) are formed Light guide arrangement ( 5 ) according to claim 1, characterized in that the light extraction structures ( 90 ) as oriented in the light guide ( 80 ) formed anisotropic scattering particles are formed. Light guide arrangement ( 5 ) according to claim 1, characterized in that the light extraction structures ( 90 ) a maximum of 5% of the surface of the light transmission surface ( 83 ) in whose area they are arranged. Mounting device ( 1 ) for fixing a retroreflective license plate ( 2 ) on a motor vehicle comprises the following features: a. a holder ( 10 ), which is designed i. a retroreflective license plate ( 2 ) with a two-dimensional shield plate to hal and ii. to be attached to a motor vehicle in such a way that the 10 ) held retroreflective license plate ( 2 ) is mechanically fixed to the vehicle, and, b. a light guide arrangement ( 5 ) according to claim 1, wherein the light guide ( 80 ) of the light guide arrangement ( 5 ) with the retroreflective license plate ( 2 ) on the front side of the areally extended shield plate of the retroreflective license plate ( 2 ) is arranged. Illuminated retroreflective license plate assembly ( 100 ), comprising the following features: a. a retroreflective license plate ( 2 ) with a two-dimensional shield plate, b. a light guide arrangement ( 5 ) according to claim 1, wherein the light guide ( 80 ) of the light guide arrangement ( 5 ) on the front side of the areally extended shield plate for illuminating the retroreflective license plate ( 2 ) is arranged. A vehicle with a holding device for a retroreflective license plate ( 2 ), comprising the following features: a. a license plate holder adapted to provide a retroreflective license plate ( 2 ) to be held with a planar extended shield plate such that the held by the license plate holder retroreflective license plate ( 2 ) is mechanically fixed to the vehicle, and, b. a light guide arrangement ( 5 ) according to claim 1, wherein the light guide ( 80 ) of the light guide arrangement ( 5 ) with the retroreflective license plate ( 2 ) on the front side of the areally extended shield plate of the retroreflective license plate ( 2 ) is arranged. Method for producing a light guide arrangement ( 5 ) for illuminating a vehicle-mounted retroreflective license plate ( 2 ), characterized by the following method steps: a. Providing at least one light source ( 22 b. Providing a planarly extended transparent light guide ( 80 ) with a front light passage surface ( 81 ) and a rear light passage surface ( 83 ), wherein the light guide ( 80 ) in the region of a light passage surface 83 ) arranged Lichtsauskoppelstrukturen ( 90 ), one of the running direction L of the in the optical fiber ( 80 ) guided light dependent Lichtauskoppelvermögen, and c. Establishing an optical connection between the light source ( 22 ) and the extensively extended light guide ( 80 ), such that the light source ( 22 ) emitted light in the light guide ( 80 ) is coupled and guided in a running direction L in this. Method according to claim 16, characterized in that the light guide ( 80 ) is produced by injection molding. Method according to claim 17, characterized in that the light extraction structures ( 90 ) during injection molding of the light guide ( 80 ) in one of the light transmission surfaces ( 83 ) are formed. Method according to claim 16, characterized in that the light guide ( 80 ) is produced by extrusion. Method according to claim 19, characterized in that the light extraction structures ( 90 ) after the extrusion of the light guide ( 80 ) by rolling with a structured roller in one of the light transmission surfaces ( 83 ) are formed.