WO2005100016A2 - Light-emitting panel and optically effective foil - Google Patents

Abstract

A light-emitting panel comprises a plurality of non-housed LED chips and a foil which covers a plurality of LED chips so as to protect them from outside influences and to influence at least in part the light emitted by the LEDs, for example converting its frequency. The foil is a conversion foil or a diffuser foil, i.e. it contains fluorescent dyes and/or diffusers. The fluorescent dye (also called conversion dye) and/or the diffusers are embedded in a first laminated structure. A second laminated structure is arranged on the side of the first laminated structure that faces the light-generating elements. All the layers of the first laminated structure and all the layers of the second laminated structure have a similar refraction index. On the contrary, there is a substantial difference between the refraction index of the layers of the first laminated structure and the layers of the second laminated structure. The refraction index of the layers of the first laminated structure is low, for example lower than 1.5, and the refraction index of the layers of the second laminated structure is as high as possible, for example higher than 1.5. The transition between a boundary layer of the first laminated structure and a boundary layer of the second laminated structure is not flat but rather has boundary surfaces which form an angle to the lamination plane or are possibly corrugated. According to another aspect of the invention, non-housed LED chips may be covered with a sheath which contains the conversion dye.

Description

LIGHT-EMITTING PANEL AND OPTICALLY EFFECTIVE FILM

The invention relates to the field of light panels with LEDs, i.e. of sectionally flat light transmitters with a plurality of light-emitting semiconductor diodes (LEDs) as light sources.

Such light panels, which also have the advantage of being able to be assembled, are known from the documents EP 1 055 256 and WO 03/023857 and also from WO2004 / 102064.

With such light panels, long-term stability, even under difficult conditions (temperature, humidity, exposure to pollutants), as well as cost-effective manufacture, are among the basic requirements. There is also a need for many applications to adapt the relatively narrow-band emission spectrum of LEDs to the respective needs. With frequency conversion using fluorescent dyes, the highest possible efficiency should be achieved on the one hand and the best possible homogeneity on the other hand.

It is an object of the invention to provide technical solutions for light panels from these points of view. According to a first aspect of the invention, a light-emitting panel is provided which has a plurality of unhoused LED chips and a film which covers a plurality of LED chips to protect them from environmental influences and at least partially influences the light emitted by them, for example frequency-converted.

“Panel” is understood to mean an element that is at least sectionally flat, which can be dimensionally stable or flexible and contains a plurality of light-generating elements, preferably arranged in a regular grid. In the context of this document, the light-generating elements are always LED chips, i.e. unhoused LEDs.

Optically effective films for converting the light color and / or for filtering certain light colors are known per se in connection with electroluminescent light sources such as LED or OLED. Examples which refer to OLED and / or to LED can be found in the documents WO03021622, WO03020846, US6653778, JPll 199781. Examples which only refer to OLED can be found in the documents TW474038, US2002113546, JP2001164245. Optically effective films in the sense of lens arrays or the like are also known per se in connection with electroluminescent light sources such as LED or OLED. Two examples from many of these are the documents US6654175 and US2003150916.

The invention stands out from this prior art in that a (single) optically effective film covers a plurality of LED chips in such a way that they are shielded from them by environmental influences - in particular by moisture. According to the first aspect of the invention, in addition to the function .optical effect 'also realizes the functions, protection' with a single, inexpensive element to be produced: a film.

In none of the known examples discloses an optically effective film, which would also only be suitable for a protective function against aggressive gases and liquids and against water and water vapor for the electroluminescent light sources and their electrical connections and, in the case of conversion or filtering of light, for perceive the dyes used. Consequently, none of these documents also discloses a film which would have long-term stability in the chemical, mechanical and optical properties of the film:

Long-term stability with regard to the chemical properties means that the protective functions mentioned above are retained for at least 50,000 operating hours, for example, even at operating temperatures of up to 120 ° C. Long-term stability with regard to the mechanical properties means that under outdoor weather conditions and under mechanical alternating loads for at least 50,000 operating hours, no embrittlement and no cracking occur at operating temperatures of up to 120 ° C. Long-term stability with regard to the optical properties means that the film in the visible light range, for example after at least 20,000 operating hours, but better only after 50,000 operating hours, may have a transmission loss of at most 20% even at operating temperatures of up to 120 ° C.

It has been shown that, for example, two classes of materials are very suitable as materials for such films according to the invention: fluoropolymers and transparent silicones. Because of their mechanical properties, these are well known as materials per se, but have so far been used for optical applications not considered (fluoropolymers) or not considered as films. Another suitable class of materials are the polycarbonates. The transparent materials, such as PMMA, PC, PE, PET, which are mostly used in connection with LED and / or OLED, however, meet the requirements either in terms of temperature stability and / or in terms of long-term optical stability Not often.

In addition to the above-mentioned or similar highly transparent, long-term stable and temperature-stable materials, it is possible to use thin layers of highly transparent, temperature-stable materials in which, for example, the light transmission in the visible range decreases over time. It is possible to choose the layer thickness of such a material so that the decrease in transmission only plays a minor role. An example of such a material is PI resists, which have an excellent but slightly decreasing transparency, a high resistance to most chemicals and a very good temperature resistance. The advantage of newly developed PI resists is that they can be applied and cured in layer thicknesses between 1 and 10 μm using conventional methods, in the cured state they have extremely high optical refractive indices (1.65 to 1.9) and thus for the production of micro-optical refractive elements (fresnel-like elements) are predestined.

The materials mentioned can be combined well with soluble or highly viscous materials; These can be applied to a base film made of the materials mentioned or other transparent materials by processes such as coating, spraying, etc. and can at least partially harden there. As a soluble material, amorphous fluoropolymers are available, for example, from Dupont under the brand name Teflon AF. This material is in certain perfluorinated solvents (eg FC75 or FC40 from 3M) are soluble and can be applied in this state in thin or thick layers by methods such as spinning, spraying, dipping, etc. on suitable carriers. It has an excellent transparency for visible light and an outstanding long-term stability like the other fluoropolymers.

The protection offered by the materials mentioned against aggressive gases and liquids as well as against water and water vapor can be significantly improved by vapor deposition or sputtering with an inorganic protective layer such as SiO _x , SiN _x O _x or TiO _x . This requires inorganic protective layers with a thickness of a few 100 nm. Such an additional protective layer produced in a thin-film process can in some circumstances also provide sufficient stability for light-emitting panels according to the invention if the film material is otherwise less suitable for performing a protective function.

With at least one layer or with a combination of several layers of the materials discussed, stable protection of an LED array can be guaranteed for a long time.

If the optically active film is a conversion film (that is, the conversion of the light emitted by the LEDs into secondary light with a different light wavelength), the necessary conversion dye (also called phosphorus) can be protected by the film itself against chemical influences. This can be ensured, for example, by a multilayer structure of the film. In such a system, the necessary dyes can be introduced between at least two layers of the materials mentioned, so that "above" and "below" the layer of dyes or phosphorus are sufficiently thick Protective material is present. Such a structure prevents gradual degradation, as can occur with dyes located near the film surface. Degradation of the dyes is practically completely prevented by the additional coating of the two protective layers with an additive inorganic protective layer, that is to say, for example, with the SiO _x - SiN _x O _x or TiO _x layer which is a few 0J μm thick.

Under certain circumstances, the protective film can also contain additional, more opaque transparent materials if they have special desired properties, such as high refractive indices. These are preferably present in layers so thin that their clouding does not endanger long-term stability, for example by choosing the thickness of the thin layers between a maximum of 1 micrometer and a maximum of 20 micrometers, and / or by selecting the thickness of the thin layers so that the resulting absorption is less than 15%, preferably less than 10%.

The production of a dye layer embedded between two layers can include, for example, that the two layers are laminated onto one another; Before lamination, the surface of at least one of the foils is sprinkled with dye, and dye can also be rolled into one of the layers. As a second possibility, a material with a (conversion) dye (e.g. a mixture of dissolved Teflon AF and the necessary amount of dye) is applied and cured before the lamination of the two layers. This can be done at temperatures between 200 ° C and 400 ° C, for example at temperatures between 250 ° C and 350 ° C. In a third possibility, the mixture of dissolved Teflon AF and the necessary amount of dye is replaced by a mixture of transparent silicone and the necessary amount of dye. In this case, the top FEP film is not laminated on, but only rolled up because the silicone offers sufficient adhesion. Multi-layer optically effective protective films can also be produced, for example with a first dye layer which has a converting action and a second dye layer (or filter layer) which acts as a filter. Alternatively, conversion dyes which cannot be mixed with one another can also be used in different layers.

The conversion dyes or filter dyes do not have to be present over the entire surface of the film. For example, it is possible to use a single dye that is only present in at least one zone of the protective film. In this way, the screened protective film can show any pattern of two colors. For example, it is feasible for green LEDs to convert from green LED to zone by zone, thus producing the well-known green-white pattern, for example, from signs.

Of course, it is also possible to arrange several different conversion and / or filter dyes in different zones. With suitable methods, such as knife coating or spraying on with masks, this can be done in a single layer. However, it is also possible to arrange different dyes in different zones in separate layers. In the latter way, it is also possible to produce color patterns that run into one another by at least partially overlapping the zones with different dyes. The arrangement of different conversion or filter dyes in different zones can be pushed very far in the sense of ever smaller zones. For example, it is easily possible to assign a different color to each individual LED in the LED array, even though blue LEDs are used throughout. But you can go further. With photolithographic processes, for example, it is easily feasible to generate a pixel pattern with different conversion or filter dyes on an optically effective protective film backlit by the LED array with monochromatic light, in which the pixels are significantly smaller than the zone illuminated by an LED, the pixels of different colors can of course be arranged in different layers. In this way, mixed colors that are otherwise not easily feasible can be generated, for example.

To generate the optical functions light bundling, light expansion or light deflection, it is possible that at least one of the outer surfaces and / or one of the inner surfaces of the protective film, if any, is provided with flat optically active elements which act like lenses or prisms. Such flat optical elements are, for example, fresnel-like refractive elements or micro-optical diffractive elements which are resolved into ring or strip zones. Both types of optical elements can be produced, for example, in fluoropolymers or in epoxy resin layers or in other plastics, for example by means of embossing. Corresponding structures can be produced in the silicones discussed, for example, by applying a silicone layer to a carrier layer, that is to say, for example, to a fluoropolymer layer, then pressing an embossing tool into the silicone layer and finally at least partially curing the silicone layer.

As an alternative or in addition to embossing micro-optical elements in the sense of Fresnel-like lenses or prisms, the protective film can have structures for effecting a light deflection, for example by deep-drawing the film so that at least locally, for example, shell-like zones in the sense of the surfaces of cylindrical lenses and / or there are rotationally symmetrical lenses, these shell-like zones being backfilled with a suitable transparent optical material, for example with silicone. The protective film can have additional elements for diffuse scattering of the light, such as, for example, micro hollow glass spheres.

The two types of optical elements mentioned (refractive / diffractive) differ, in terms of manufacture, essentially by the depth and fineness of the structures to be produced and thus by the manufacturing processes for the necessary tools. Methods for creating such structures are known.

However, it should also be mentioned that the diffractive elements can in principle be constructed in two different ways. The first type consists of a large number of finest, groove-like structures which are embossed, for example, into transparent (transmitted light elements) or non-transparent (mirror elements) material. The dimensions of these structures are in the order of a few micrometers down to dimensions that are smaller than the wavelength of the light used. The second type, with corresponding dimensions, consists of non-transparent lines, which are applied to transparent material, for example, by sputtering metal and then photolithographically structuring the metal.

If fresnel-like refractive elements are used, it is known that the desired optical effect becomes stronger for a given element depth with an increasing refractive index of the materials used. This means, for example, that when such optical elements are incorporated into the fluoropolymers discussed, which have a low refractive index between approximately 1.3 and 1.35, significantly deeper and / or finer-resolution structures must be produced than, for example, when using a silicone with a refractive index of up to 1.5. Even greater effect can be achieved by using an, if necessary additional, layer of the already discussed PI resist or another similar material with a refractive index from 1.65 to 1.9.

Diffractive optical elements have an optical behavior that depends on the wavelength of the light. The PI resist discussed, which is suitable for micro-optical refractive elements, has a refractive index which, for example, decreases continuously from blue to red light from 1.75 to 1.65. In combination, these two facts mean that the optical formation is not at least simple with monochromatic, and therefore also white light with correspondingly constructed elements. In order to avoid this difficulty, it can be advantageous in a multilayer film if the monochromatic light first passes through the bundling optics, optimized to the corresponding wavelength, and only then does it pass through the necessary color conversion layers. Such a layered structure can be produced by lamination, etc., according to the above statements.

To generate the optical functions “diffuse light scattering”, at least one diffusely scattering surface and / or one diffusely scattering layer can be used in addition to one of the structures described above. This can be achieved by roughening one of the existing outer and / or inner surfaces of the described optically effective protective film. Possible processes such as, for example, etching processes, sandblasting, brushing, etc. are well known for this. Alternatively, a diffusely scattering thin or thick layer can also be produced, for example, by introducing a large number of small bodies scattering the light into a transparent silicone resin or into amorphous Teflon AF. It is advantageous if these bodies absorb the light that strikes them as little as possible, but only reflect them. Diffuse light distribution can then be achieved through a large number of reflections even if the individual reflection is not diffuse. Scattering bodies that well meet the requirement for the lowest possible absorption are, for example, micro-hollow glass spheres that are available on the market down to diameters of approx. 1 μm.

Starting from one of the protective film structures described, a further possibility for generating the optical functions light bundling, light expansion or light deflection can be described. All of the film structures described can be deformed - at least up to 10% local elongation, but mostly significantly more. Such reshaping can take place, for example, by deep drawing. This fact can be used to locally reshape the protective film at least at one point in such a way that shell-like zones are created in the sense of the surfaces of cylindrical lenses and / or of rotationally symmetrical lenses and / or of prisms. If these shell-like elements are backfilled with a transparent material, this backfill acts like a corresponding refractive optical element.

Instead of the production processes described above by means of lamination or differently designed layers of different layers, a conversion film or diffuser film can also be produced, for example, also by extrusion of a mixture already containing the dye or diffusion body or by another suitable process.

According to a particularly preferred embodiment, the film is held by spacing elements at a distance from the light-emitting surface of the LED chips in such a way that there is no thermal bridge between the film and the chips. For example, spacer elements can be arranged in the film between the film and a carrier element that carries the LED chips and makes electrical contact Form of rods or webs made of a non-metallic thermally poorly conductive material, for example. Plastic or in the form of a transparent layer. It may also be the case that the LED chips are surrounded by pressure-resistant elements that protrude the LED chip at height with apertures or concave-like openings, and that the film is applied to the common surface of these elements as an additional protective film. Instead, the film can also be attached to spacer elements attached between the elements or to thermally insulating spacers attached to an upper side of the diaphragm or concave mirror-like elements.

According to a first sub-aspect of the first aspect, the film is a conversion film or a diffuser film, ie it contains fluorescent dyes and / or diffusers. The fluorescent dye (it is also called conversion dye here) and / or the diffusers are embedded in a first layer structure. A second layer structure is arranged on the side of the first layer structure facing the light-generating elements. The first and the second layer structure each consist of one or more layers. All layers of the first layer structure and all layers of the second layer structure preferably each have a similar refractive index, ie the refractive index differences between layers within the first or second layer structure are small, for example a maximum of 0.1 or a maximum of 0.05. On the other hand, there is a substantial difference between the refractive indices of the layers of the first layer structure and the layers of the second layer structure, the refractive index of the layers of the first layer structure being small - for example less than 1.5, and the refractive index of the layers of the second layer structure being as large as possible - for example larger than 1.5 - is. The transition between a boundary layer of the first layer structure and a boundary layer of the second layer structure is not flat, but has boundary surfaces which form an angle or which are possibly undulated to the layering plane. In a preferred embodiment, the transition forms a cross section "Zigzag" structure, that is, the interfaces alternately form a negative and a positive angle to the layering plane. The angle does not have to be constant in the amount, but can possibly vary and, for example, also have a sawtooth-like cross section.

The reason for this structure is as follows: In principle, light emitted by a conversion dye or by a diffuser (hereinafter referred to as "secondary light") is not directed. As a result, substantial portions of the secondary light are directed back in the direction in which the light-generating elements are located ( so to the "back") or emitted laterally and get lost. Because of the construction according to the invention, light emitted to the rear is refracted at an oblique interface to the perpendicular. For a large part of the - statistically distributed - angles of incidence there is a flatter angle to the layer structure, so that a large part of the light reflects back at a rear interface of the second layer structure, i.e. away from the first layer structure, and remains in the film. After a new refraction at the transition between the second and first layer structure, the light can be emitted to the front, so it is useful. If the film contains diffusers, the light can be scattered again through diffusers.

The efficiency of this arrangement can be increased even if the surface, ie the transition between the layer structure and an ambient medium, also contains non-flat interfaces. For example, the course of this transition can follow the course of the transition between the first and the second layer structure, so that the thickness of the first layer structure is approximately constant as a function of the position in the layer plane. “Approximately constant” means, for example, that the expansion in the z direction (ie the direction perpendicular to the layering level) does not vary by more than a third of the average thickness. Particularly preferred Embodiments in which the position in the z direction of the transition between the first and the second layer structure and that of the transition between the first layer structure and the surrounding medium vary by a value which is at least 2/3 of the thickness of the first layer structure. Then light guide effects within the first layer structure are practically prevented.

Overall, the structure according to the first sub-aspect thus brings an increased radiation efficiency for a given luminous output of the light-generating elements.

The concept of the first sub-aspect can also be used independently of the first aspect of the invention, for example by applying the above-described layer system with the first and second layer structure directly to an OLED (organic light-emitting element). It can also be implemented in any conversion film that can be used in any way. Such a conversion film still has, for example, a carrier film to which the layer system according to the invention, which may not be mechanically stable, is applied. Instead of a conversion film, the layer system according to the invention can also be implemented in a mechanically rigid conversion plate.

According to a second sub-aspect of the first aspect of the invention, the comparatively small spectral width of the emission spectra of light-emitting diodes and the absorption spectra of conversion dyes is concerned, and the generation of a homogeneous radiation characteristic of the light-emitting panel.

For this purpose, the panel with an array of electrically contacted LED chips per LED chip or unit of several LED chips has a concave-like or diaphragm-like optical element through which the emitted electromagnetic Radiation can be concentrated to a comparatively small solid angle around an emission direction. Such optical elements are drawn in the international patent application PCT / CH2004 / 000263 (in particular in FIGS. 3a-3h and their description) as well as in the Swiss patent applications 663/04 (FIGS. 1b-1d) and 1425/04. The content of these patent applications is expressly referred to in this regard, and the content thereof is hereby made part of this application. According to the second sub-aspect, the conversion film is arranged at a distance d from a carrier element carrying the LED chips and the optical elements. The optical elements are shaped and / or arranged in such a way that subgroups of several LED chips or units of LED chips are formed, the emitted light of which coincides in the plane of the film - that is, at a distance d.

In a first variant, this allows LED chips with slightly different primary light wavelengths to be used in each subgroup if the film is a conversion film. Then the sum of the emission spectra of the LED chip can be relatively wide. This makes it possible to achieve a constant radiation characteristic with regard to brightness and wavelength (color) for the secondary light generated. This is particularly advantageous where a constant visual impression is important.

According to a second variant, the film is a diffuser film and the LED chips are RGB chips with the appropriate mixture (ie chips with primary light emission in the colors red, green and blue, the spectrum of which complements white light or any color light ). The embodiment according to the invention ensures that the panel really appears to the viewer as white and not on closer inspection as a superimposition of red, green and blue dots. This variant is particularly advantageous in the case of screen-like structures, where the composition of the red, green and blue light sector (or pixel) is shown in Time function varies. It is also very suitable for panels in which the color of the lighting changes as a whole or in large sectors; These are used, for example, in airplanes, where the color of the lighting can vary between white, blue and red].

In both variants, the conversion or diffuser film can be supplemented by a mask layer, which allows light to enter or possibly exit into the film or out of the film only at those points where the primary light rays cross. Edge effects can be hidden in this way.

Particularly preferred - but not mandatory - is the simultaneous use of both sub-aspects, i.e. the combination of the film with the first and second layer structure and the non-flat transition with the second sub-aspect explained above.

According to the various embodiments of the first aspect, the film can be arranged such that there is no thermal bridge to the LED chips and that the film therefore remains comparatively cool. This also allows the use of conversion dyes, the quantum efficiency of which drops sharply at temperatures around 50 ° C or at temperatures slightly above. In comparison to the prior art, significantly more conversion dyes are available, including particularly efficient and / or particularly inexpensive inorganic dyes.

According to a second aspect of the invention, a panel is provided with a carrier element and a multiplicity of unhoused LED chips, each LED chip or each unit being a small number of one another arranged LED chips is assigned a shell which contains the conversion dye and rests directly on the LED chip / the LED chips or one or more transparent protective layers surrounding them locally. The thickness of the entire shell is such that it follows the shape of the chip. The shell is produced, for example, in a thin film process. The thickness is preferably less than the thickness of the — often flat — LED chip, preferably at least by a factor of 2, for example at least by a factor of 4. It is, for example, at most 10 μm, for example at most 5 μm or at most 2μ. This is significantly less than the feasible minimum chip thickness of 50 to 100 μm today. As an alternative criterion, one can define that the volume of the layer containing dye per LED and associated pad for a wire bond does not exceed the volume of the LED chip by more than a little, for example by a factor of 2 or not at all.

The applied conversion dye is preferably applied so thinly that it is homogeneously distributed or contains a layer enriched in one layer, so that it is - if necessary after curing - so thin that it reproduces the shape of the chip homogeneously. This means that the thickness of the layer measured in a light emission direction over the chip does not vary by more than 30%, preferably not more than 20%, particularly preferably not more than 10%. In this case it is ensured that each beam of short-wave light emerging from the chip (UV radiation is also referred to as "light" according to the definition used in this text) sees exactly the same amount of dye and thus different colors are avoided at different exit locations. This is particularly advantageous in the case of certain newer chips which are available and which, by means of their shape, for example by means of inclined side faces, ensure substantially increased light emission efficiency. With newer chips, which are offered by the company Cree, for example, more than 70% of the light exits to the sloping side surfaces. The conversion layer - it is generally used to convert the LED chip emitted short-wave light to a greater wavelength - preferably covers all open sides of the LED chips as evenly as possible.

For series production, the coating of the chips on a panel is applied simultaneously in a .batch 'process, for example in a vacuum using a mask, in such a way that defined zones are formed, in each of which a chip and possibly a contact pad / contact pads are embedded by the wire bonds that contact them /are.

In addition to the at least partial frequency conversion of the electromagnetic radiation generated by the chips, the casing also fulfills a protective function.

The following methods can be used as techniques for applying the layer - with or without a mask:

Spraying: The conversion dyes can be mixed with a suitable, optically transparent carrier material in such a way that, firstly, they are contained in sufficient concentration in the carrier material and secondly that the viscosity of the mixture is produced so that it can be sprayed on in thin layers. Since the organic dyes in particular have an ever better life, the better they are protected against water, water vapor and oxygen, optically transparent carrier materials such as transparent silicones or amorphous fluoropolymers, such as Teflon AF from Dupont, are used with advantage. When using the powdery inorganic dyes, this mixing is carried out by mixing into the carrier material (diluted with a solvent if necessary) (hereinafter also referred to as matrix material). As a rule, the dye grains have diameters of significantly more than one micrometer. It it is also possible to mix in nanostructured inorganic dyes, whose grain size is smaller than the light wavelength. With nanostructured dyes there is no light scattering on dye grains. Processes for the economical production of such nanostructured dyes are under development in many places worldwide. When using organic dyes, which are usually also supplied in powder form, the same procedure is of course possible in principle. However, organic dyes can also be dissolved in suitable solvents in a very low concentration, ie in a few percent by volume and less, and mixed in this form with the carrier material. This can be done particularly efficiently if the carrier material can be diluted with the same solvents. For example, many organic dyes and many suitable silicones can be dissolved in toluene. In this way, a homogeneous mixture can be produced, in which, after the solvent has been expelled, the optically transparent carrier material contains the dye in such a way that the light is not scattered. In general, the use of dissolved organic dyes is particularly preferred since no scattering is caused. The sprayed mixture typically contains at most a few percent dye, often less than 1% or even less than 0.1%.

A spraying process can be carried out in such a way that the entire surface of an LED array can be coated with a thin layer of the sprayed material at almost the same time. In particular, it is also possible to drive the spraying process in such a way that not only the flat surfaces, but also the inclined or approximately vertical side surfaces of the LED chip are coated.

Thin-film process: According to a second possibility, the conversion dyes can also be used with a so-called thin-film process such as vapor deposition or sputtering or all of their further developments and varieties such as for example chemical vapor deposition (CVD), physical vapor deposition (PVD), each including subspecies such as laser CVD etc., plasma coating, laser coating, etc. can be applied. For the sake of simplicity, all of these processes are summarized under the term vacuum coating in the following explanations.

These processes are characterized in that the dyes can be applied in very thin layers and that they cover the LED chip evenly on all open surfaces. The density of the resulting layer can be controlled so that the light emitted by the LED chip is absorbed completely or only to a certain extent and converted.

The layer thicknesses mentioned are generally only a few nm to a few 100 nm, for example up to a maximum of 500 nm.

Since the organic dyes in particular have an ever better lifespan, the better they are protected against water, water vapor and oxygen, it is advantageous if an appropriate protective layer is created in the course of the vacuum coating - and if possible without breaking the vacuum.

This is possible by running the vacuum coating process in such a way that at least two different materials are coated simultaneously and in succession. One material is then the conversion dye or a conversion fragments mixture, while the other material is an optically transparent protective material such as SiO _x or SiO _x N _x . The optically transparent protective material is at least directly on the dye layer, but better below and above the dye layer and even better with the dye of a layer is mixed. The process can then proceed, for example, in such a way that first of all an SiO _x or SiO _x N _x layer of some 10 nm thickness is generated. This is followed by a layer of some 10 nm thickness in which conversion dyes and SiO _x or SiO _x N _{x are present} in a suitable mixture, and finally another SiO _x or SiO _x N _x layer of some 10 nm thickness can follow. In this way, an organic dye can be completely incorporated into protective material and thus optimally protected.

The terms "below" and "above" or "below" and "above" in this text generally refer to the direction of radiation, i.e. “Above” is the direction in which light is emitted, while “below” denotes the rear side of the light source, ie the light panel, as seen from the LED chips.

Such a layer or layer sequence with a protective material such as SiO _x or SiO _x N _x has the further advantage that, of course, not only the organic dyes, but also all the components underneath them, in particular the LED chip and its electrical connections, are optimally opposed protects chemical environmental influences, so that the life of the entire LED array can be expected to improve even further.

According to a first sub-aspect of the second aspect, the conversion envelope - for example with the aid of a mask - is applied to the panel with chips that have already been electrically contacted (bonded). The chip and the electrical contacts are then completely protected from oxygen and passivated. If the conversion sleeve is applied in a vacuum, all vacuum processes can take place without breaking the vacuum. According to a second sub-aspect of the second aspect, the conversion envelope is applied to the panel which has not yet electrically contacted or only electrically contacted (through which the bonding 'is attached) on its underside. Then the electrical contacts for the second electrical contact - both the "pads" and a contact area on the front of the chips - must be left free when the conversion sleeve is provided. A subsequent contact can be made, for example, using a transparent, electrically conductive material, which is applied locally to a surrounding area of the chip, or by means of a metallic material forming radial stripes on the chip, which saves on the one hand a wire bond and on the other hand enables a potential to save space: a contact pad can be used as a Narrow strip surrounding the chip and need not be present as a relatively large area formed next to the chip, which makes it possible to increase the packing density, at least in embodiments in which it is not limited by the heat removal.

In this and other cases, in order to ensure the functionality of the finished LED array, it is necessary that the resulting color conversion layer is only present at defined locations on the LED array. It can also be useful, for example, if the color conversion layer is "misused" at certain other locations on the carrier to produce a locally passivated location, for example in the sense of a solder stop.

Such a structured color conversion layer can be produced by the application process using a so-called shadow mask, which only allows access to the areas to be coated. Since the accuracy with which such a mask has to be manufactured and applied must be in the range of up to ± 0.1 mm, such a process is easy to master. A shadow mask can - with a correspondingly somewhat reduced accuracy - also be used in the spraying process described above.

In this text, "fluorescent dyes" or "phosphors" always mean dyes that absorb electromagnetic radiation of a first wavelength and then emit electromagnetic radiation of a second wavelength, which is different from this. Phosphorescent dyes - i.e. Dyes of the type mentioned, in which a certain time elapses between absorption and emission - are expressly meant.

Organic or inorganic dyes are known as such fluorescent dyes. Inorganic dyes of this type exist in large numbers. Known

Examples are: Y ₃ Al ₅ Oι ₂ : Ce, ZnS: Cu; Mn, ZnS: Cu or SrGa2S4: Eu2 + etc.

There is an almost unlimited selection of organic dyes of this type, also known as laser dyes. Examples are the dyes known by the trade name Lumogen from BASF, Yellow 172 from Neeliglow, India, and laser dyes such as Coumarin 6, Coumarin 7, Fluorol tGA, DCM, pyridine 1,

Pyrromethenes 546, Uranine and Rhodamine 110, which are available from numerous retailers.

Embodiments of the invention are described in more detail below with reference to drawings. The drawings show:

1 shows a cross section through a film for a light panel according to the first sub-aspect of the first aspect of the invention. FIG. 1 a shows a view of a possible course of the transition between the first and the second layer structure in a film according to FIG. 1.

Fig. Lb shows a schematic cross section through a light panel according to the first aspect of the invention.

Fig. 2 shows a schematic cross section through a section of a light panel according to the second sub-aspect of the first aspect of the invention.

3 shows a qualitative representation of the superimposition of the emission spectra of several different LED chips and, for comparison, an absorption spectrum of a conversion dye

Fig. 4 and Fig. 4a shows a cross section through the principle of a reflex OLED film.

Fig. 5 shows a detail of a light panel according to the second aspect of the invention in cross section.

6 and 6a each show a section of a further light panel according to the second aspect of the invention.

Figures 7a to 7e show the schematic, not to scale cross-sections of different versions of protective films with a single-layer coloring or Phosphor layer for light conversion or filtering of a light emitting panel according to the first aspect.

FIGS. 8a to 8d show the schematic cross-sections, not to scale, of different designs of protective films with different colored or phosphor layers arranged in multiple layers for light conversion and / or filtering.

FIGS. 9a to 9d show the schematic, not to scale, cross sections of different versions of protective films with single-layer or multi-layer in zones or pixel-like different coloring or phosphor layers for light conversion and / or filtering.

10 shows the schematic cross-section, not to scale, of a protective film with coloring or phosphor layers for light conversion or filtering and an additional layer for diffuse light scattering.

Film 10 shown in FIG. 1 serves to convert at least partially electromagnetic radiation (light, UV light) emitted by light-emitting elements into light of a longer wavelength. In the selected illustration, primary radiation strikes the film from below and is emitted as secondary radiation towards the top (“towards the front”). The film has a first layer structure consisting of a first protective layer 11, a conversion layer 12, ie a layer which is transparent per se at least one conversion dye, and a second protective layer 13. On the side of the first layer structure facing the light-emitting elements, a second layer structure is present, which in the example shown consists of a single layer, namely the reflection layer 15 consists. The transition between the second protective layer 13 and the reflection layer 15 is not flat, but instead consists of inclined surfaces, that is to say an angle to the layering plane - that is to say the horizontal. For example, as outlined in FIG. 1 a, the surfaces can run in such a way that four partial surfaces (left drawing) or six partial surfaces (right drawing) run in the manner of pyramids towards a tip 13.1. The pyramid shape shown is not mandatory; For example, there may also be uneven surfaces or a different shape may be selected. It is only important that a majority of the interfaces forming the transition form an angle to the layering level. Under certain circumstances, this can also be achieved by a wavy transition.

The angle of the interfaces to the layering plane - that is, in the arrangement shown, the angle between the interface normal and the vertical - is between 10 ° and 60 °, preferably at least 12 ° and at most 45 °.

Particularly good results are achieved if, in addition to the transition between the first and the second layer structure, the transition between the first layer structure and the surrounding medium - generally. Air - that is, the outer surface of the film has interfaces which form an angle with the horizontal. The angle of these interfaces to the layering plane is preferably between 12 ° and 45 °.

In principle, the courses of the two transitions mentioned can be independent of one another. According to a preferred embodiment, however, the interfaces are designed such that the variation in the position of the transition between the first and second layer structure - that is to say the pyramid height corresponding to the "deflection" in the z direction - is at least 2/3 of the thickness of the first layer structure is. The deflection can, for example, correspond to the amount of the thickness of the first layer structure. Then the course of the interfaces must be correlated. Ideally, the areas follow one another as drawn in FIG. 1, so that the z-dimension of the first layer structure remains constant.

In this embodiment, the lateral light transport is completely prevented.

The layers of the first layer structure have a refractive index that is as small as possible and approximately the same, for example “= 1.3. For example, the conversion layer - apart from the conversion dyes - can be a fluoropolymer, for example a plastic available under the trade name Teflon. The first and second protective layers can also consist of Teflon, for example. Alternatively, the protective layers can also be made of materials that have a slightly higher refractive index, for example between 1.4 and 1.5. Glass or SiO _x , which is applied by vapor deposition or sputtering, is also suitable. Another possible material is sprayed silicone. The layers of the first layer structure must generally have the following properties:

Optically high transparency in a wavelength range from 400 nm to 10000 nm; in this area the transmissivity should be at least 90% with a thickness of 100 μm.

- Minimal outgassing at temperatures of up to 100 ° C, otherwise bubbles can occur in production or operation. The conversion layer must survive the lamination or spraying and curing of the two protective layers without damage and without outgassing. If the protective layers are made of Teflon, this means when laminating at up to 350 ° C for a few seconds.

The first and second protective layers should be water and water vapor tight and only allow a small diffusion of molecular oxygen. Ideally, they are thin compared to the layer containing the dye.

The reflection layer or the layer of the second layer structure is / are transparent like the first and second protective layers and has / have a high refractive index, for example 1.6 <«. For example, the polyimide reflective layer

consist. The reflection layer can be very thin, for example 10 μm or less, and is therefore a significantly poorer one

Have transmissivity, for example a transmissivity of at least 90% with a thickness of 20 μm. The efficiency of the film is even better if the reflection layer has an even higher refractive index. There are transparent materials with refractive indices well above 2, for example GaP, GaN, SiC, or the so-called HMO glasses (heavy metal oxide glasses). However, some of these materials are thin-film materials (i.e. can currently only be applied using thin-film processes). Since the thickness of the reflection layer has to compensate for the “stroke” of the conversion layer (ie the amplitude of the change in the z position of the transition between the first and second layer structure), this means a very small stroke and therefore preferably a very thin conversion layer of up to less than 1 μm. Suitable dyes

(nanostructured, or dissolved in the conversion layer) are already partially available or in the works in laboratories. The total layer thickness of the layers of the first layer structure is, for example, between 10 μm and 200 μm, preferably less than 100 μm. The thickness of the reflection layer varies in the illustrated embodiment as a function of the x and y position; it can also be between 10 μm and 200 μm. If the entire film is thin, the film is applied to a transparent carrier (for example 1 mm acrylic glass).

In contrast to the embodiment described here, the second protective layer 13 can also have a high refractive index; it then belongs to the second layer structure.

In addition, all layers should have high long-term stability, i.e. show no yellowing and no embrittlement. The loss in transmissivity, for example, is a maximum of 10% after an operating time of 100,000 hours at 50 ° C. The materials do not become brittle under the same conditions with an operating time of 100,000 hours at 50 ° C.

The mode of operation of the conversion film is as follows (see also the sketched beam path in Fig. 1): electromagnetic primary radiation entering from below - for example blue or ultraviolet light or also visible light of a different wavelength - couples through the reflection layer and hits the dyes in the conversion layer. Longer-wave light is emitted here in all directions. A considerable part of the longer-wave secondary light emitted to the rear (ie in the direction back to the light-generating elements) is refracted by the transition structure 13 in such a way that the angle to the layer plane becomes flatter and that at the lower boundary surface of the reflection layer - that is generally that Interface between the reflective layer and air - much of the light is reflected. That light is then broken again at the transition to the first layer structure and is only reflected back to a small extent as it arrives almost perpendicular to the inclined surfaces due to the first refraction. The light can propagate unhindered through the layers of the first layer structure and due to the small refractive index of the layers of the first layer structure and the sloping surfaces in the transition area to the surrounding medium, a large percentage is also radiated forward.

Model calculations show that the percentage of light emitted to the front can be increased from less than 25% (flat conversion film with a refractive index of approx. 1.5) to approx. 40-50% by using a first and a second layer structure with refractive indices 1.3 or 1.8 are used and the transition between the first and second layer structure consists of interfaces tilted by approx. 20 ° -30 ° with respect to the horizontal. The percentage can be increased to approximately 70% by, as in FIG. 1, also assembling the outer surface of the film from oblique pyramid surfaces (angle: optimally also between 20 ° and 30 °).

The second protective layer in particular is optional and can be omitted. Instead of a conversion layer, the film 10 can have a diffuser layer, i.e. instead of a dye, diffusers are present in the corresponding layer. In this case, in contrast to the description above, the secondary light reflected back cannot propagate unhindered to the outside but can be scattered again by the diffusers, so it serves as primary light again.

The entire film can be attached to a flat carrier layer - for example glass - with good transmissivity. A light panel according to the invention is shown schematically in FIG. 1b. The panel has a carrier element 101 made of, for example, an electrically conductive material and a layer sequence 102 of electrically insulating and electrically conductive, structured layers. Electrically conductive, structured layers can, for example, form a specific pattern of conductor tracks and contact pads. The structured electrically conductive layers and possibly also the carrier element serve for the electrical contacting of the LED chips 103, for which purpose wire bonds 109 may also be required. The structuring of the conductive layers is not shown in the figure. The light panel has one or more base elements 104 mechanically connected to the support element with aperture or concave mirror-like openings 105. In the embodiment shown, the openings have a parabolic mirror-like surface which, together with the aperture effect, contributes to the fact that light is directed towards the front (in the figure after above) is emitted. With regard to a possible construction of carrier element and base elements, reference is made to the already mentioned patent applications PCT / CH2004 / 000263, CH 663/04 and CH 1425/04.

A film 100 with conversion dye is either located directly on a surface of the base elements or is arranged at a distance d from the carrier element by spacing elements. In contrast to the film from FIG. 1, the film drawn in FIG. 1b is designed in such a way that only the transition between the first and second layer structure consists of inclined surfaces. Spacers are preferably thermally well insulating (ie thermal conductivity less than 1.5 W / m, preferably less than 0.5 W / mK) and can be present in the form of blocks, rods, bars or similar on the base elements 104 (rods 106) or directly Support on the carrier element or its coatings (webs 107). They can also be designed as a transparent layer 108, which covers the base elements. It is also possible to fasten the entire film (+ backing layer) in a “frame” that it has in common with the LED panel. Such a frame can also be open on several sides (to all sides), for example only from a limited number, for example, four "posts". Open to the side is advantageous because air can then circulate and the heat transport to the film becomes even smaller.

The spacing, thermal and therefore mostly also electrically insulating elements 106, 107, 108 can also be used in connection with conversion foils which do not have the described structuring with the first and second layer structure. The thermal decoupling between a film spanning a large number of LED chips and the LED chips or their carriers and possibly base elements is then important. As already explained, this allows the use of dyes, the efficiency of which, as a function of temperature, rapidly decreases at temperatures around 50 ° C.

On the other hand, the film according to FIG. 1 can also be used without the basic elements shown in FIG. 1b. The bundling effect that these basic elements have is not absolutely necessary, but it increases the efficiency of the coupling into the first layer structure. The light panel in FIG. 2 is also constructed, for example, according to the principle described in FIGS. 1, 1a and 1b. It differs from the light panel of Fig. Lb in the following properties:

The carrier element 23 is locally spatially bent into shells or - if it is not mechanically rigid - is applied to a locally shell-shaped support element. As a result, there is an overlap of those emitted by the LED chips 25 of a subgroup - such a module can consist, for example, of four to sixteen LED chips - and of the diaphragm-like or concave mirror-like ones Elements 24 bundled light beams at a distance d from the carrier element. The distance d corresponds to the distance of the film from the actual panel base body 22. The entire carrier element can have a large number of grid-like, shell-like sections, each with a subset of LED chips.

- The conversion film 20 (or diffuser film) optionally has an additional mask layer 21 on its rear side (i.e. the side facing the LED chips), which only lets light through where the actual light rays are directed. This will hide any edge effects.

The LED chips emit in different wavelengths. This does not mean that each chip in a sub-group must necessarily have an individual wavelength, but that at least two chips in a sub-group have different emission wavelengths. Examples of a subgroup of nine chips are wavelengths of 455, 457.5, 460, 462.5, 465, 467.5, 470, 472.5 and 475 nm if the film is a conversion film or 3 red, 2 green and 4 blue chips if the film is a diffuser Slide is.

In contrast to the embodiment shown, the hollow-gel-like or diaphragm-like optical elements 24 can also be interconnected, that is to say parts of a base element 14 of the type shown on the right in FIG. 1b.

The advantage of this procedure for the case of several blue light-emitting LED chips is illustrated in FIG. 3. There are implanted but realistic ones Emission spectra 32 of nine LED chips (fine solid lines) and their sum 31 (thick solid line), each standardized, drawn. Also shown is the absorption spectrum 33 of a conversion dye. The illustration shows that if the central emission wavelength of an individual LED chip is shifted, for example due to temperature change, aging, etc., the percentage of light absorbed can also change massively, for example by less than 5 nm. This will - as can be observed in practice - the color of the light panel perceived by the viewer change markedly, for example the panel can be perceived as green instead of white. In contrast, in the case of a spectral distribution according to the invention, the

Absorption efficiency insensitive to a shift of the emission spectrum by a few nm. The maximum of the total emission spectrum is always close to the absorption maximum even with shifts of + 5 nm.

FIG. 4 shows an organic light-emitting element (OLED) with a conversion film according to the invention laminated on. The actual light-generating part is shown in simplified form. It has a light-emitting layer 47, which is given as a layer made of transparent material with a small refractive index (for example Teflon, n = 1.3). This layer is surrounded by a first, reflective electrode 48 (for example made of aluminum) and a second, transparent electrode 46 (for example ITO). Laminated onto it - or attached in some other way - is the reflection film with a second layer structure consisting of reflection layer 45 and a first layer structure consisting of the optional second protective layer 43, the conversion layer 42 and the first protective layer 41. With regard to the possible materials, refractive indices and geometry of the transition structure 44 and Operation is referred to the description of Figure 1. The efficiency of the OLED structure is significantly better if the light-emitting layer also has a “zigzag structure” (ie has boundary surfaces which form an angle to the layering plane, see FIG. 4a) Therefore, a space 148 is created behind the) flat reflection layer 144 (ie the second layer structure) and the electrodes and light-emitting layers. This space or these spaces 148 are then filled with air or an inert gas, for example 144 against air increases the efficiency and there is no lateral light transport in the light-emitting layer 146 of the OLED.

FIG. 5 shows a cross section through a section of a light panel according to the second aspect of the invention. On a carrier element shown in simplified form. 51 - it can be a metallic substrate provided with an insulating layer and a structured conductor layer, a flex circuit board provided on both sides with a (partially structured) conductor layer - for example made of Kapton - or some other suitable substrate - is an unencapsulated LED chip 52 shown. In contrast to the simplified illustration of the preceding figures, the LED chip is drawn in a typical form, in which, in addition to a front emission surface 52.1, it also has lateral oblique emission surfaces 52.2. The percentage of light emitted by these side emission surfaces is substantial. The whole structure including wire bond 53 (e.g. gold wire, diameter 25 μm) is local - i.e. in a

Environment of the LED chip 53 - provided with a layer structure. This consists of an optional first protective layer 54a, a layer 54b containing the conversion dye and also an optional second protective layer 54c. The thickness of the entire layer structure is such that it follows the shape of the chip, that is to say that it is not or not significantly thicker than this. The total thickness is, for example, less than or equal to 2 μm. The first and second protective layers exist for example each made of SiO _x , the conversion layer 54b made of co-sputtered SiO _x and dye.

For the series production of the light panel according to the second aspect of the invention, the entire panel is provided with the layer structures at the same time in a batch process. For this purpose, a mask is positioned in such a way that defined zones are created, in each of which a chip and, if necessary, the contact pad of the wire bond already attached is embedded. The first protective layer, the conversion layer and, if necessary, the second protective layer are then sputtered on in sequence. Instead of a sputtering process, another vacuum coating process can also be used. All processes can run without breaking the vacuum. Instead of vacuum coating processes, other manufacturing processes are also conceivable, for example knife application using a mask.

According to a variant of the embodiment of FIG. 5, not shown, the layer structure (“the conversion envelope”) not only covers the surroundings of each LED chip with the layer 54b containing the conversion dye, but also the entire panel or at least several partial areas of the panel that have LED chips. In this variant, the mask can be omitted during manufacture, and pads for subsequent contacting of the entire structure (ie for connecting the panel or parts thereof to an electrical voltage source) can either be covered or the conversion envelope can be broken through at the appropriate points The depicted variant with the locally delimited envelope is particularly useful if there are metallic reflectors in the vicinity of each chip, which provide for heat dissipation. In this case, coating these reflectors with a conversion layer is generally rather undesirable. Illuminated panels according to the second aspect of the invention have the advantage that they can be very thin, including the conversion layer, and that a layer structure can be provided in a simple batch process, which can perform both a conversion and a protective function.

FIG. 6 (lower drawing) shows a light panel according to the second sub-aspect of the second aspect of the invention. The conversion envelope - i.e. however, the layer structure comprising optional first and second protective layers 64a, 64c and conversion layer 64b is designed such that the front contact surface 62a of the chip 62 is free of it. The layer structure also does not cover contact areas ('contact pads') of the carrier element 62 (i.e. the substrate). For this purpose, there is a transparent, electrically conductive layer 65 which locally covers the chip and its surroundings and establishes electrical contact between the peripheral contact surfaces of the carrier element and the front contact surface 62a of the chip. As already stated, this embodiment has the advantages that no wire bond is required and that there is a potential to increase the packing density.

A method for applying the conversion envelope can be configured as follows:

In a first step, the chips are positioned on the carrier element, whereupon the rear contact surface 62b of the chips is connected to a corresponding contact surface of the carrier element by means of a die bond process. A first and a second mask 66 and 67 are then positioned such that only one area around each chip is exposed, but the front contact surface 62a of the chips and also the contact pads of the carrier element are covered. A representation of the two masks 66, 61 can be found in the upper drawing of the figure 6. To cover the front contact surface, the second mask 67 has a shielding element 67b, which is held, for example, by a few radially extending wires 67c. The shielding element 67b can rest on the chip since there are no wire bonds which could be damaged by the mask. As a third step, the layers of the conversion envelope are applied in a vacuum batch process, such as by sputtering. Then the second mask 67 is pivoted away, exposing the front contact surface of the chips and the contact pads. The coating is then carried out using ITO or another transparent, electrically conductive material. The vacuum is preferably not broken during the process.

The first mask 66 can possibly be omitted in the manufacturing process, namely when all LED chips (or all LED chips of a partial area) are electrically connected in parallel. Another alternative is to contact by means of a narrow metallic strip running radially in the area of the LED chip.

The relative positional accuracy between each chip of a panel and each corresponding mask part in the x and y directions (i.e. both directions in the plane of the carrier element) must be within a maximum of + 70 μm. This is still achievable even for large panels. The front contact surface of the chips to be shaded has a diameter of, for example, 120 μm. So that the radial wires do not cause unwanted open paths in the conversion envelope, they should be kept a minimum distance from the chip. The wires are therefore bent accordingly.

In Figure 6a embodiment is drawn according to the principle of Figure 6. The drawn section from a light panel 160 has an LED chip 162 applied to a substrate 161. This is the help of one of the second masks 67 6 mask provided with an electrically insulating, transparent protective layer 164a, which can also extend to an environment of the chip. A transparent, electrically conductive layer 165 (for example ITO) is located thereon, which brings about an electrical contact between the front chip contact surface 162a and a peripherally arranged contact pad. The transparent, electrically conductive layer 165 is structured, for example, with the aid of a mask corresponding to the first mask from FIG. 6. As an alternative to the transparent, electrically conductive layer, contact can also be made via strip-shaped, metallic elements, for example via aluminum strips. The entire structure is provided with a layer system which is applied to a carrier, namely a carrier film 166a - here made of amorphous Teflon. In the illustrated embodiment, the layer system is the layer system described above with a second layer structure 166b (high-index reflective layer) and a first layer structure 166c (conversion layer and optionally protective layers made of, for example, Teflon or SiO _x ). The layer system is preferably applied flat, ie it covers at least a partial area of the entire panel, which contains a plurality of LED chips.

The conversion film (consisting of carrier film 166a and layer system) can be produced over a large area and subsequently applied hot to the panel so that it follows the shape of the chip. This can be done using a die or a gas with a slight positive pressure. It is best to cover the entire area of the LED panel with the conversion film and, where necessary, to subsequently remove the film locally by etching, or lasering or cutting and peeling (or similar).

The conversion film addresses the problem of the light reflected by the conversion dye, which is also present in the embodiments of FIGS. 5 and 6. It must be prevented that a large part of the secondary light is simply swallowed again by the chip. The conversion film of Figure 6a acts like that Embodiment of Fig. 1 and brings a strong increase in the proportion of coupled secondary light. The conversion film with the low refractive index carrier film (n = 1.3) has the small disadvantage that less primary light is coupled out of the chip compared to n = 1.5. Thanks to the slanted side surfaces of the chip, this reduction is only 1%, which of course is more than compensated for by the advantageous effect of the conversion film. Overall, there is a significant increase in overall efficiency.

The conversion film can - as an example only - be produced as follows:

A shaped surface with pyramids (according to FIG. 1 and FIG. La or comparable) is used. Such existent, for example in the form of anisotropically etched silicon. This is coated with a thin film, which later enables the film to be removed. Then the conversion layer or the first layer structure is produced, for example, by co-sputtering. The structure is then filled with the reflection layer (i.e. the second layer structure), for example in the form of a resist made of polyimide, or a sol-gel process for HMO glass. Then the carrier film made of transparent Teflon is laminated onto the resulting flat surface, and the mold is pulled off and may be reusable.

The sequence of layers exchanged between the ITO layer and the conversion layer in comparison to FIG. 6a in FIG. 6a can of course also be used in embodiments in which no layer system structured according to the invention with the first and second layer structure is used. The conversion film of FIG. 6a can also be used in the construction analogous to FIG. 5, the conversion film then being used in places of any that may be present Wire bonds can have corresponding recesses so that the contacts are not damaged during application.

The possible construction of conversion foils according to the first aspect of the invention is discussed in the following figures. The films according to the figures can - but do not have to - be designed in addition to the drawn features according to the first sub-aspect and thus have structures which contain a first and second layer structure, interfaces between the first and second layer structure forming an angle with the layering plane or are curled. The foils can also be used according to the second sub-aspect of the first aspect.

FIG. 7a shows the schematic cross-section, not to scale, of a two-layer protective film, the first layer 211 in the surface area protected by the second layer 212 containing dye or phosphorus 213 for light conversion or filtering. The two layers 211 and 212 consist of one. highly transparent, long-term stable protective film, for example made of Dupont FEP or PFA films available on the market. The amount of dye 213 required for the desired conversion or filtering of a light color is introduced into the film 211 on one side.

This introduction can take place, for example, in such a way that the necessary dye 213 is sprinkled onto the foil 211, which is heated beyond its glass point (in our example, therefore, to about 300 ° C.) and rolled in with slight pressure. The total thickness of the film 211 is, for example, between approximately 50 to 200 μm, that of the layer containing dye 213, for example, between 20 to 100 μm.

The second film 212, which is likewise heated, for example between 20 and 100 thick, is laminated on directly after this process.

The result is an extremely cost-effective protective film with an almost homogeneous transition from film 211 to film 212, which contains the desired dye 213 in its center, which is protected on both sides.

Under certain circumstances, a disadvantage of the structure according to FIG. 7a can be that it is difficult to maintain a large homogeneity of the dye distribution over the entire film surface.

The schematic, non-scale cross section of a protective film shown in FIG. 7b eliminates this possible disadvantage.

This protective film also essentially consists of two layers 211 and 212 of a highly transparent, long-term stable protective film, for example of FEP or PFA films from Dupont available on the market. The same can apply to transparent layers of the protective films of the embodiments described below. In addition to these film materials, other film materials known per se, for example, are also suitable The dye 213 required for color conversion or filtering is homogeneously mixed into a suitable matrix material 214. This mixing process takes place independently and with great accuracy. The matrix material 214 can consist, for example, of highly transparent, dissolved amorphous Teflon AF from Dupont or of a highly transparent, highly viscous silicone.

If silicone is used as the matrix material, the two foils 211 and 12 are prepared on one side, for example by means of etching or a suitable plasma treatment, in such a way that silicone adheres to them. Prepared foils are available directly from Dupont.

The structure according to FIG. 7b is produced, for example, by applying the homogeneous mixture of dye 213 and matrix material 214 to the film 211 in a homogeneous thickness using a suitable method such as, for example, doctor blades.

If dissolved Teflon AF is used as the matrix material, the solvent is then driven off, which can happen at temperatures of approx. 100 ° C. The second film 212 is then laminated on at temperatures in the region of approximately 300 ° C.

If silicone is used as the matrix material, the silicone may at first be partially cured. The second film 212 is then laminated on and the silicone is cured. The thickness of the foils 211 and 212 are, for example, between approximately 20 to 200 μm, that of the matrix layer 214 containing dye 213, for example, between 20 to 100 μm.

FIG. 7c shows a protective film structure according to FIG. 7b, the protective function and long-term stability of which is improved by the entire film, with a suitable vacuum method such as sputtering or vapor deposition, subsequently on both sides with an additional inorganic protective layer 215, some 0J to 10 μm thick is coated, for example, from SiO _x or SiN _x O _x . Of course, it would also be possible to coat a film according to FIG. 7a accordingly. A one-sided coating with an inorganic protective layer is also possible.

The structure according to FIG. 7d differs from that according to FIG. 7c in that the two layers of inorganic protective material 215 are located in the interior of the film in the immediate vicinity of the matrix material 214 mixed with dye 213.

This has the advantage that, for example in the case of bending loads, the protective layers 215 do not crack or this at least only occurs when the loads are significantly higher.

The protective film according to FIG. 7d is produced, for example, by providing the two films 211 and 212 with the inorganic protective layer 215 on at least one side before the composite is subsequently created. FIG. 7e shows a structure according to FIG. 7c, in which the two external inorganic protective layers 215 are protected against cracking by two additional layers 216. The two additional protective layers 216 are, for example, also made of FEP film, a thickness of 10 to 50 μm providing sufficient protection.

FIG. 8a shows the schematic, not to scale, cross section of a multi-layer protective film, the first layer 221 in the surface area protected by the second layer 222a containing dye or phosphorus 223a for light conversion or filtering. The second layer 222a in turn contains dye or phosphor 223b in the surface area protected by the next layer 222b for light conversion or filtering.

Such structures, as shown in FIG. 8a but also in FIGS. 8b, 8c, 8d, with several layers of color are useful, for example, if a gradual color conversion - for example from ultraviolet to blue and then from blue to white - is to take place and / or if, for example, after a color conversion, excess unconverted light is to be filtered out.

The dyes 123a and 123b are introduced and the foils 121 with 122a and 122a with 122b are joined together, for example, in layers as described in the structure according to FIG. 7a.

It is also possible in a corresponding way to produce structures with even more different layers of conversion or filter dyes. A disadvantage of the construction according to FIG. 8a can, under certain circumstances, be that it is difficult to have a large homogeneity in the distribution of the dyes 223a and 223b to be observed over the entire film surface. The cross-section of a multilayer protective film shown in Figure 8b, schematic, not to scale, _resolves this potential disadvantage.

This protective film also essentially consists of layers 221, 222a and 222b of a highly transparent, long-term stable protective film, for example of FEP or PFA films from Dupont available on the market. The dyes 223a and 223b required for color conversion or filtering are homogeneously mixed into suitable matrix materials 224a and 224b. This mixing process takes place independently and, for example, with great accuracy. The matrix materials 224a and 224b can consist, for example, of highly transparent, dissolved amorphous Teflon AF from Dupont or of a highly transparent, highly viscous silicone.

If silicone is used as the matrix material, the foils 221, 222a and 222b are prepared on one side, for example by means of etching or a suitable plasma treatment, in such a way that silicone adheres to them. Prepared foils are available directly from Dupont.

The structure according to FIG. 8b is produced in layers according to the procedure described with reference to FIG. 8b. The thickness of the foils 221, 222a and 222b are, for example, between approximately 20 to 200 μm, that of the matrix layers 224a and 224b containing dye 223a and 223b, for example between 20 to 100 μm.

FIG. 8c shows a protective film structure according to FIG. 8b, the protective function and long-term stability of which is improved by the entire film subsequently, using a suitable vacuum method, such as sputtering or vapor deposition is coated on both sides with an additional, some OJ to 10 μm thick, inorganic protective layer 225, for example made of SiO _x or SiN _x O _x . Of course, it would also be possible to coat a film according to FIG. 8a accordingly.

The structure according to FIG. 8d differs from that according to FIG. 8c in that the two layers of inorganic protective material 225 are located in the interior of the film in the immediate vicinity of the matrix material 224a or 224b mixed with dye 223a or 223b.

This has the advantage that, for example in the case of bending loads, the protective layers 215 do not become cracked, or at least this only occurs when the loads are significantly higher. The protective film according to FIG. 8d is produced, for example, by providing the two films 221 and 222b with the inorganic protective layer 225 on at least one side before the composite is subsequently created.

FIG. 9a shows a protective film constructed essentially according to FIG. 7b, which differs from the film according to FIG. 7b in that the mixture of dye and matrix material 233 is not present over the entire area, but only in zones. The gaps 234 between the zones 233 can at most be filled with the unmixed matrix material or simply be hollow.

The zone-by-zone application of the mixture 233 and at most the unmixed matrix material into the intermediate spaces 234 can be carried out, for example, in the manner of screen printing, that is by knife coating with appropriate screens. A structure according to Fig. 9a is for this suitable a two-tone based on monochromatic light

To create the appearance of the protective film.

Figure 9b differs from Figure 9a in that zones 233a and 233b contain different dyes. Of course, there may be other zones with other dyes. A structure according to FIG. 9b is suitable for producing a multicolored appearance of the protective film based on monochromatic light.

FIG. 9c essentially differs from FIG. 9b in that the zones with different dyes 233a and 233b, similar to that shown in FIG. 8b, are arranged in different layers, at most separated by an intermediate film 232a. Firstly, this can have the manufacturing advantage that a very sharp transition from color to color can be produced. Second, zones 233a and 233b can - as shown in the left part of FIG. 9d - partially overlap, which can be used to produce additional color effects.

The right part of FIG. 9d illustrates the possibility of arranging zone mixtures 233a and 233b or zones with unmixed matrix material 234a and 234b in different positions in a pixel-like manner in such a way that several such pixels are shined through by the light of an LED - indicated in FIG. 9d below , In addition, as shown on the left in FIG. 9d, the pixels of different layers can partially or completely overlap.

For example, if the light color of the LED is blue and there are, for example, mixtures 233a and 233b, one of which converts the blue light to green and the other the blue to red, one can determine the viewing distance appropriate pixel fineness for the viewer - standing and not dynamically changeable - generate colored images with almost any color variety.

For protective films of this type, which are to be viewed from distances of a few meters and more, the necessary resolution of the pixels can certainly be produced by means of screen-printing processes. For protective films that are to be viewed from small distances, it is possible, for example, first to apply the dyes in layers over the entire surface and then to produce the necessary fine pixel structures photolithographically.

FIG. 10 shows a protective film constructed in principle according to FIG. 7a, which, in addition to the optical function of light color conversion or filtering, fulfills the optical function of diffuse light scattering. In principle, the film could of course also be constructed in accordance with any one of FIGS. 1a to 4d.

In the case shown and in all other conceivable cases, a further layer 254 is present in addition to the other structure of the protective film. Although this layer 254 is intended to produce diffuse light, it advantageously consists of one of the previously highly permanently transparent, long-term stable plastics such as FEP or silicone. This is due to the fact that films that become cloudy do not also generate diffuse light but mainly absorb light. In our case, however, light absorption is completely undesirable.

Diffuse light with as little absorption as possible can be generated by the highly transparent plastic 254 with, for example, metallic bodies 255 that reflect the light as completely as possible, or with, for example transparent, partially light-transmitting and partially reflecting hollow bodies 255, for example hollow glass spheres, are filled.

For the production of such a layer, for example filled with hollow glass spheres, for example, dissolved amorphous Teflon AF or highly viscous silicone is mixed with hollow glass spheres available on the market, then applied, for example by means of doctor blades, to the otherwise finished protective film and then cured.

The embodiments described above are mere examples of how the invention can be implemented. There are a variety of other options.

This application is based on the priority of three Swiss patent applications 664/04, 1425/04 and 1957/04, the content of which forms part of this application and which are incorporated herein by reference.

Claims

PATENT CLAIMS

Light-emitting panel with a plurality of unhoused, mounted on a support and electrically contacted light-emitting diodes (103, 25), the panel being flat in sections, characterized by an optically effective, liquid-tight film (10, 100, 20) which is attached in this way that it covers a plurality of diodes to protect them from environmental influences and influences the light emitted by them.

2. Light-emitting panel according to claim 1, characterized in that the film is held by spacing elements (106, 107, 108) at a distance from the LED chips, the spacing elements being, for example, in a regular grid or flat over the panel distributed and made of non-metallic material, or the spacing elements are attached to the edge of the panel.

3. Light-emitting panel, according to claim 1 or 2, characterized in that the protective film contains dyes or phosphors for frequency conversion or filtering.

4. Light-emitting panel according to one of the preceding claims, characterized in that the protective film contains optically refractive or diffractive structures for collimation, focusing, widening and / or deflection of light which is generated by the diodes.

5. Light-emitting panel according to one of the preceding claims, characterized in that the film includes a first and a second layer structure, which are arranged next to one another and together form a layer system which defines a layering plane, which is the xy plane of a Cartesian coordinate system, the The first layer structure has at least one layer (12) containing fluorescent dye or diffusers, the refractive index of the or each layer of the first layer structure being smaller than the optical refractive index of the or each layer of the second layer structure, the second layer structure being arranged on the side facing the light-emitting diodes and wherein the transition (13) between the first and the second layer structure includes interfaces which form an angle to the layering plane, or wherein the transition is undulated.

6. The light-emitting panel as claimed in claim 5, characterized in that an outer boundary of the film, that is to say a transition between the first layer structure and an ambient medium, contains interfaces which form an angle with the layering plane, or that the outer boundary is corrugated.

7. Light-emitting panel according to claim 6, characterized in that the variation of the position in the z direction of the transition between the first and the second layer structure in the Cartesian coordinate system is at least 2/3 of the thickness of the first layer structure and the course of the transition between the first and the second layer structure correlates with the course of the transition between the first layer structure and the surrounding medium, in such a way that the thickness of the first layer structure is at least approximately constant as a function of the x and y position.

8. Light-emitting panel according to one of claims 5 to 7, characterized in that the angle between interfaces between the first and the second layer structure and the xy plane between 12 ° and 45 °, preferably less than 45 ° and for example between 15 ° and 35 ° is.

9. Light-emitting panel according to one of claims 5 to 8, characterized in that the first layer structure, in addition to the layer containing fluorescent dye or diffusers (12), also a first transparent protective layer (11) which closes the film against the surrounding medium and preferably also one of the has the second protective layer on the opposite side of the fluorescent dye or diffuser-containing layer (12) arranged second transparent protective layer (13).

10. Light-emitting panel according to one of claims 5-9, characterized in that the refractive index of each layer of the first layer structure is at most 1.5, preferably at most 1.4, and the refractive index of each layer of the second layer structure is at least 1.6, preferably at least 1.7.

11. Light-emitting panel according to one of the preceding claims, wherein each LED chip or each unit of a plurality of LED chips arranged next to one another is assigned a concave mirror-like or diaphragm-like optical element (24) through which the LED chip or LED Chips emitted light can be bundled in each case in a certain solid angle about an optical axis, the concave mirror-like or diaphragm-like elements of at least one sub-group having a plurality of LED chips or units of LED chips being aligned such that the optical axes of the sub-group converge and that the light generated by the LED chips of the subgroup is at least partially superimposed at the location of the conversion film, and wherein at least two LED chips of the subgroup have emission wavelengths that differ from one another.

12. Light-emitting panel according to claim 11, characterized in that the film contains a fluorescent dye and that the LED chips of each sub-group emit blue and / or ultraviolet light in different wavelengths.

13. Light-emitting panel according to claim 11, characterized in that the film contains diffusers and that each sub-group has at least one blue light, green light and red light-emitting LED chip.

14. Light-emitting panel according to one of claims 11 to 13, characterized in that an opaque mask layer is provided on a side of the film facing the LED chips, which has recesses where the solid angle of the LED chips of the subgroup or Overlap subgroups.

15. Layer system for at least partial conversion of primary light incident from a first side into secondary light emitted on a second side, comprising a first and a second layer structure, the first and the second layer structure being arranged next to one another and together forming a layer system which is a layering level X- y plane of a Cartesian coordinate system defined, the first layer structure having at least one fluorescent dye or diffusers Containing layer for at least partial conversion of the primary light into the secondary light, wherein the refractive index of the or each layer of the first layer structure is smaller than the optical refractive index of the or each layer of the second layer structure, and wherein the transition between the first and the second layer structure includes interfaces which form an angle to the layering plane or where the transition is wavy.

16. Layer system according to claim 15, characterized in that an outer boundary of the layer system, that is, a transition between the first layer structure and an ambient medium, contains interfaces which form an angle to the layering plane, or that the outer boundary is corrugated.

17. Layer system according to claim 16, characterized in that the variation of the position in the z direction of the transition between the first and the second layer structure in the Cartesian coordinate system is at least 2/3 of the thickness of the first layer structure and the course of the transition between the first and correlates the second layer structure with the course of the transition between the first layer structure and the surrounding medium, in such a way that the thickness of the first layer structure is at least approximately constant as a function of the x and y position.

18. Layer system according to one of claims 15 to 17, characterized in that the angle between interfaces between the first and the second layer structure and the xy plane between 12 ° and 45 °, preferably less than 45 ° and for example between 15 ° and 35 ° is.

19. Organic light-emitting element with a light-emitting structure (42) which is arranged between a first, non-transparent electrode and a second, transparent electrode, and with a layer system according to one of claims 15 to 18 arranged on the side facing the transparent electrode ,

20. Light-emitting panel with a carrier element (51, 61) and a plurality of unpackaged LED chips (52, 62) arranged thereon, at least some of the LED chips being provided with a conversion dye-containing envelope which is applied directly to the LED chip , the thickness of this casing being such that the casing follows the shape of the LED chip.

21. Light-emitting panel according to claim 20, characterized in that the thickness of the envelope is a maximum of 10 microns.

22. The light-emitting panel as claimed in claim 20 or 21, characterized in that the casing contains an outer second protective layer (64c), a layer (64b) containing the conversion dye and optionally a first protective layer (64a) lying directly on the LED chip.

23. Light-emitting panel according to one of claims 20 to 22, characterized in that the casing is only present locally in the vicinity of each LED chip and sections are not provided with the casing between the LED chips.

24. Light-emitting panel according to one of claims 20-23, characterized in that a contact surface of the LED chip is electrically connected to a contact pad via a wire bond (53), and that the first contact surface and the contact pad are coated with the sleeve.

25. Light-emitting panel according to one of claims 20-23, characterized in that a contact surface (62a) of the LED chip and a contact pad are free of the shell, and that the shell, the contact surface and the contact pad with a transparent electrically conductive layer (65) are coated, or that the contact surface and the contact pad are electrically connected to a strip-shaped metallic layer.

26. Light-emitting panel according to one of claims 20-23, characterized in that the casing is so thin that its volume per LED chip and associated contact area exceeds the volume of an LED chip by a factor of at most 2, and furthermore all open sides the LED chip covered.

27. Light-emitting panel according to one of claims 20 to 26, characterized in that the casing contains a layer system according to one of claims 15 to 18.

28. A method for producing a light-emitting panel, in particular according to one of claims 20-26, wherein a carrier element 61 is provided with a plurality of LED chips and is then coated, at least in regions, with a shell, which shell, in a batch process Conversion dye for at least partial conversion of LED Contains chips of emitted electromagnetic radiation to long-wave radiation.

29. The method according to claim 28, characterized in that the conversion dye is applied by means of a vacuum coating process.

30. The method according to claim 29, characterized in that after the application of the dye and preferably also before the application of the dye, an optically transparent protective layer is applied, the protective layer or layers being preferably applied by means of a vacuum coating method.

31. The method according to any one of claims 28-30, characterized in that transparent material is applied simultaneously with the application of the conversion dye, so that it is mixed with the dye in the applied layer.

32. The method according to any one of claims 28-31, characterized in that the layer thickness of the dye layer is at most 500 nm.

33. The method according to any one of claims 28-32, characterized in that the contact pad and the contact surface are electrically connected to one another via the wire bond before coating.

34. The method according to any one of claims 28-33, characterized in that the coating with the conversion dye takes place through a shadow mask, so that a structured color conversion layer is formed.

35. The method according to claim 34, characterized in that the coating with the sleeve is carried out through a second mask (67), which covers the first contact surfaces (62a) and the contact pads, and in that the subsequent coating with the transparent, electrically conductive material a first mask (66) is passed through, which covers spaces between LED chips, so that the electrically conductive material of adjacent LEDs does not come into contact with one another.