Composite material with a photoluminescent material embedded in a transparent matrix

Abstract

Composite material (10) comprising at least one photoluminescent material (12) which is embedded as a light source in a transparent matrix (14) wherein a refractive index (n P ) of at least one photoluminescent material (12) and a refractive index (n M ) of the matrix (14) have a difference of at most ±0.2, and wherein the photoluminescent material (12) comprises at least one inorganic phosphor from the group - (M 1-x EU x ) 10 (PO4)6(Cl,F)2, in which M is chosen from one or more elements from the group Sr, Mg, Ca and Ba and x = 0.01-0.12; - M 1-y EU y MgAl 10 O 17 , in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr and y = 0.01-0.9; - M 1-z EU z MgAl 10 O 17 , in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr and z = 0.01-0.9; - (M 1-p EU p )6BP5O 20 , in which M is chosen from one or more elements from the group Sr, Mg, Ca and Ba and p = 0.01-0.9; - (Sr 1-q EU q )4Al 14 O 25 , in which q = 0.01-0.9; - Mg4Ge 1-r Mn r (O, F)6, in which r = 0.001-0.06; or - M 1-s EU s (Mg 1-t Mn t )Al 10 O 17 in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr, s = 0.01-0.7 and t = 0.05-0.5.

Description

[0001] The invention relates to a composite material with at least one photoluminescent material, which is embedded as a light source in a transparent matrix. The invention further relates to a display device with such a composite material and to a method for operating such a display device.

[0002] In many everyday applications, there is a desire to be able to display information such as logos, images, text, and the like on a large scale on shop windows, building facades, vehicle windows, and so on. Furthermore, it is desirable that the surface on which this information is to be presented, when switched off (i.e., when the information is not displayed), is visually indistinguishable, or at least as indistinguishable as possible, from similar surfaces that are not suitable for such information display. For example, when switched off, it should be as inconspicuous as possible that a shop window is capable of displaying such information.

[0003] Until now, transparent organic light-emitting diodes (OLEDs) have predominantly been used as the luminescent composite material for these applications. With the help of such OLEDs, it is possible, for example, for a suitably equipped shop window pane to display information when the OLED is switched on or excited, while remaining at least partially transparent when the OLED is switched off or not excited, meaning it is partially transparent to electromagnetic radiation in the visible spectral range of approximately 380 nm to approximately 780 nm.

[0004] However, a disadvantage of currently available OLEDs is that their application is limited to relatively small areas, significantly less than 1 m². 2is limited. Furthermore, due to the required electrode layers, OLEDs significantly reduce the transparency of substrate materials such as glass, acrylic glass, plastics, etc. This means that the light-emitting surface is visible even when switched off and has a milky, i.e., only partially transparent and often yellowish, appearance.

[0005] A well-known alternative to using OLEDs involves projecting light onto a substrate such as glass or similar material, which is coated with a diffusing layer to selectively scatter or reflect the incident light. This diffusing layer can cover a significantly larger area compared to OLEDs.

[0006] However, such scattering layers inevitably lead to a strong change in the optical appearance, so that, for example, appropriately equipped glass surfaces no longer appear transparent, but milky or translucent.

[0007] The publication DE 10 2009 036 481 A1 describes a photoluminescent granulate made from a hardened mixture comprising a transparent lightfast matrix containing at least one photoluminescent pigment and a transparent filler.

[0008] German patent application DE 11 2011 100 435 T5 describes an optical device comprising an LED and a wavelength conversion material. A wavelength-selective surface blocks direct emission from the device and allows selected wavelengths of emission to pass through, which result from an interaction with the wavelength conversion material.

[0009] Publication US 2008 / 0 094 691 A1 describes a wavelength conversion layer with embedded crystallites containing wavelength conversion materials.

[0010] Document US 2007 / 0273282A describes an optoelectronic component that has a wavelength conversion layer which is a composite material consisting of a polymer matrix and a phosphor.

[0011] Transparent urethanes are also known.

[0012] The object of the present invention is to provide a luminescent composite material suitable for large-area display of information and which is at least substantially transparent, at least in the switched-off or non-excited state. Further objects of the invention are to provide a display device with such a composite material and a method for operating such a display device.

[0013] The problems are solved according to the invention by a composite material having the features of claim 1, by a display device according to claim 6, and by a method according to claim 13 for operating such a display device. Advantageous embodiments with expedient further developments of the invention are specified in the respective dependent claims, wherein advantageous embodiments of the composite material are to be regarded as advantageous embodiments of the display device or the method, and vice versa.

[0014] A first aspect of the invention relates to a composite material comprising at least one photoluminescent material embedded as a light source in a transparent matrix, wherein, according to the invention, the refractive index of the at least one photoluminescent material and the refractive index of the matrix differ by at most ±0.2. By selecting the transparent matrix such that its refractive index is close to that of the photoluminescent material, the composite material according to the invention is virtually "invisible" with respect to light scattering, since light passing through the composite material is accordingly not scattered or reflected, or only to an insignificant extent. Therefore, the composite material is transparent to incident electromagnetic radiation in the frequency spectrum visible to humans.In the context of the present invention, transparency means that the internal transmission of the composite material, i.e., the transmission without taking into account Fresnel reflections at interfaces, is at least 0.8, in particular at least 0.9, and preferably at least 0.95, for light in the visible spectral range at 20 °C and a layer thickness of 1 cm. The weight fraction of the photoluminescent material, or...The total percentage of all photoluminescent materials by weight of the composite material can be freely chosen between 0.1% and 99.9% by weight, for example 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%. 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9%, with corresponding intermediate values ​​being deemed to be disclosed. The at least one photoluminescent material can, in principle, be fluorescent and / or phosphorescent.Similarly, at least one photoluminescent material can be a broadband phosphor, a linear phosphor, or a mixture thereof. The matrix can consist of one material or a mixture of two or more suitable materials, whereby the matrix material(s) preferably do not photoluminescent in the spectral range visible to humans. Within the scope of the present invention, a difference of ±0.2 shall be understood to mean, in particular, differences which are, for example, 0.20, 0.19, 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, 0.11, 0.10, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01, 0.009, 0.008, 0.007, 0.006, 0.005, 0.004, 0.003, 0.002, 0.001 or less, with corresponding intermediate values ​​being deemed to be disclosed. Preferably, the magnitude of the difference in the refractive indices is as small as possible, in particular 0.This makes it possible, on the one hand, to excite the photoluminescent material by exposing it to suitable electromagnetic radiation in order to display information; on the other hand, the composite material is at least essentially transparent in the non-excited state of the photoluminescent material. Unlike OLEDs, the use of at least one photoluminescent material also makes it possible to use the composite material for large-area information display, since no electrode layers or the like are required, but only appropriate light exposure to excite the photoluminescent material. Of course, the composite material can also be used simply for illumination purposes. In the simplest case, sunlight or daylight can be used to expose the at least one photoluminescent material to light. However, one or more artificial light sources can also be used.Lighting devices are provided to excite the photoluminescent material. Therefore, the composite material can be used with exceptional flexibility and scaled to virtually any geometric shape. Depending on the mechanical properties of the matrix and the geometric design, the composite material can also be used either on its own, for example as a luminescent replacement for glass panes, or applied as a transparent coating to an additional substrate.

[0015] In an advantageous embodiment of the invention, the absorption maximum of the photoluminescent material lies outside the visible spectrum. In other words, the invention provides that the photoluminescent material, at 20 °C and a layer thickness of 1 cm, has a maximum absorption of at most 0.25, particularly at most 0.2, and preferably at most 0.1, for light in the visible spectrum. Thus, the photoluminescent material practically does not absorb in the visible spectrum and therefore appears at least approximately colorless or white in the unexcited state, so that the composite material can be not only transparent but also colorless or at least substantially colorless. This allows for a particularly inconspicuous optical design of the composite material in the unexcited state of the photoluminescent material.For example, one or more photoluminescent materials can be incorporated that are excitable by radiation invisible or barely visible to the human eye, such as deep blue, violet, near-UV, or UV radiation, and which do not, or only minimally, affect the transparency of the composite material. A further advantage is that the excitation of the photoluminescent material can be carried out in a correspondingly unobtrusive manner.

[0016] In a further advantageous embodiment of the invention, the photoluminescent material consists of particles having a mean particle diameter ≤ 400 nm, in particular < 100 nm and preferably < 5 nm, and / or a mean particle diameter ≥ 800 nm, in particular > 10 µm and preferably > 30 µm. The use of particles with such particle sizes allows for a particularly significant reduction in light scattering of the composite material. It has proven especially advantageous if the mean particle diameters are significantly smaller and / or significantly larger than the excitation wavelength(s) and / or the emission wavelength(s) of the at least one photoluminescent material. For example, the mean particle diameters can be at least an order of magnitude smaller and / or larger than the maximum or minimum excitation wavelength(s) and / or emission wavelength(s) of the photoluminescent material.Nanoscale photoluminescent materials have proven particularly advantageous in this regard.

[0017] Further advantages arise from selecting at least one photoluminescent material from a group that includes inorganic phosphors, organic phosphors, and quantum dots. This allows the optical properties of the composite material, particularly with regard to excitation and emission wavelength(s), to be optimally adapted to the specific application. Preferably, photoluminescent materials are used, individually or in combination, that scatter light in the visible spectrum as little as possible within the composite material. In addition to inorganic and organic phosphors, quantum dots are also suitable, especially quantum dots with a core-shell structure that maximizes the Stokes shift between absorption and emission.

[0018] According to the invention, the photoluminescent material comprises at least one inorganic phosphor from the group - (M 1-x EU x ) 10 (PO4)6(Cl,F)2, in which M is chosen from one or more elements from the group Sr, Mg, Ca and Ba and x = 0.01-0.12; - M 1-y EU y MgAl 10 O 17 , in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr and y = 0.01-0.9; - M 1-z EU z MgAl 10 O 17 , in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr and z = 0.01-0.9; - (M 1-p EU p )6BP5O 20 , in which M is chosen from one or more elements from the group Sr, Mg, Ca and Ba and p = 0.01-0.9; - (Sr 1-q EU q )4Al 14 O 25 , in which q = 0.01-0.9; - Mg4Ge 1-r Mn r(O, F)6, in which r = 0.001-0.06; or - M 1-s EU s (Mg 1-t Mn t )Al 10 O 17, in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr, s = 0.01–0.7 and t = 0.05–0.5. In the aforementioned summation formulas, all values ​​lying between the respective range limits are to be considered implicitly revealed. For example, the specification y = 0.01-0.9 includes the values ​​0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89 and 0.9 as well as corresponding intermediate values.As another example, the range r = 0.001-0.06 includes the values ​​0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.020, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.027, 0.028, 0.029, 0.030, 0.031, 0.032, 0.033, 0.034, 0.035, 0.036, 0.037, 0.038, 0.039, 0.040, 0.041, 0.042, 0.043, 0.044, 0.045, 0.046, 0.047, 0.048, 0.049, 0.050, 0.051, 0.052, 0.053, 0.054, 0.055, 0.056, 0.057, 0.058, 0.059, and 0.06, etc. The compositions of the photoluminescent material(s) are described by molecular formulas. These correspond to the nominal composition of the photoluminescent material(s). In reality, the exact atomic ratios can deviate slightly from the stated ideal values. A possible value for such a deviation is, for example, ±10%.It is also possible that the photoluminescent material contains other elements, which may be introduced via impurities or fluxes in the initial mixture or during synthesis, in particular (but not exclusively) boron and / or carbon and / or nitrogen and / or halogens such as fluorine, chlorine, or bromine. Evaporation of individual components during synthesis can also lead to statistically deficient composition of certain layers. For the sake of clarity, these potential effects are not always explicitly mentioned in the given molecular formulas. For example, the photoluminescent material may contain one or more phosphors from the BaMgAl group. 10 O 17 :Eu, Mg4GeO 5,5 F:Mn, Sr6BP5O 20 :Eu and Sr4Al 14 O 25The composite material can be made from or comprised of such an inorganic phosphor. This allows the composite material to be produced without a yellowish discoloration, since all the aforementioned inorganic phosphors do not absorb, or at least not significantly absorb, light in the visible spectrum, but instead emit light in the visible spectrum after appropriate excitation. In particular, these inorganic phosphors absorb light primarily in the deep blue, violet, near-UV, or UV spectral range, but practically not in the blue, green, yellow, or red spectral range. Conversely, they emit light in the blue, green, and / or red spectral range. By embedding one or more of these inorganic phosphors as photoluminescent materials in the matrix of the composite material, it can be made almost completely transparent and colorless in the unexcited state.Conversely, the color emitted by the composite material in the excited state can be freely adjusted.

[0019] In a further advantageous embodiment of the invention, the matrix comprises glass, silicone, plastic, in particular polyacrylate, polymethacrylate, polymethyl methacrylate, polycarbonate, epoxy resin, formaldehyde resin, polyacrylonitrile, polyamides, polybutadiene, polyester, polyethylene, polyurea, polypropene, polystyrene, polyurethane, polyvinyl chloride and / or polytetrafluoroethylene, ceramic and / or a non-metallic hybrid polymer material. This allows the composite material to be optimally adapted to its respective application without compromising its transparency. Suitable glasses include, for example, low-melting glasses, which can be leaded or lead-free. Examples of suitable lead-containing glasses are PbO-B2O3, PbO-B2O3-ZnO and PbO-B2O3-SiO2, while lead-free glasses can be selected from, for example, Bi2O3-B2O3, Bi2O3-B2O3-ZnO, SnO-P2O5 or ZnO-B2O3.It should be emphasized, however, that other glasses and combinations thereof can also be used as a matrix or matrix component. Furthermore, non-metallic inorganic materials produced via sol-gel processes, such as water glass, monoaluminum phosphate (MALP), or ceramic adhesives, and / or non-metallic hybrid polymer materials based on alkyl silicates, such as tetraethyl silicate (TEOS), can be used as a matrix or matrix component. Alternatively or additionally, transparent silicones, organic plastics, and / or ceramic materials are also suitable as matrix materials. In the case of one or more ceramic matrix materials, the composite material, which can then also be described as a fluorescent ceramic, can be produced to be highly transparent and at least essentially pore-free.

[0020] Further advantages arise from the matrix comprising a filler material by which the refractive index of the matrix is ​​adjusted to a predetermined value. In other words, the refractive index of the matrix is ​​fine-tuned by adding one or more filler materials to approximate or exactly match the refractive index of the photoluminescent material. The at least one filler material can, in principle, be freely selected from suitable compounds, with inorganic metal oxides such as ZrO₂, TiO₂, or Al₂O₃ proving advantageous due to their easy availability and chemical resistance. Preferably, the at least one filler material is also used in a form that does not, or at least minimally, impair the optical properties of the composite material, apart from the refractive index.In particular, the at least one filler material can also be used in the form of particles whose mean particle diameters are selected such that they cause as little light scattering as possible from the composite material. In this case, too, it has proven advantageous if the mean particle diameters of the filler material are significantly smaller and / or significantly larger than the excitation wavelength(s) and / or the emission wavelength(s) of the at least one photoluminescent material. For example, the mean particle diameters of the filler material can be at least an order of magnitude smaller and / or larger than the maximum or minimum excitation wavelength(s) and / or emission wavelength(s) of the photoluminescent material.For example, at least one of the filler materials can consist of particles having a mean particle diameter ≤ 400 nm, in particular < 100 nm and preferably < 5 nm, and / or a mean particle diameter ≥ 800 nm, in particular > 10 µm and preferably > 30 µm. Nanoscale filler materials have proven particularly advantageous in this regard.

[0021] A second aspect of the invention relates to a display device with at least one carrier element comprising at least one composite material according to the first aspect of the invention as a layer or component of a layer. The carrier element can, in principle, consist of the same material as the matrix of the composite material. Alternatively or additionally, the carrier element can consist of one or more other materials compared to the matrix of the composite material. The layer containing or consisting of the composite material can, in principle, be arranged on one side of the carrier element or on several sides of the carrier element. Furthermore, the carrier element can be coated only partially or completely.Preferably, the support element is transparent, meaning that objects behind it are at least relatively clearly visible, i.e., the support element is largely transparent to radiation of the visible spectrum. Alternatively, the support element can be translucent or opaque, so that objects behind it are not visible or at least not substantially visible. The size of the display device can be scaled almost arbitrarily by extending the lateral dimensions of the support element. This makes the display device suitable for large-area illumination and for displaying information over large areas, with at least the luminescent composite material being transparent or substantially transparent in the switched-off or unexcited state. Thus, almost any support element can be used with the luminescent material in the switched-off or unexcited state.In its unexcited state, an optically inconspicuous composite material can be provided as a layer or component of a layer and used to illuminate and / or display images, text, and other information by switching on or exciting the photoluminescent material within the layer. The layer containing the composite material can be very thin, for example, with a thickness of 2 mm, 1.9 mm, 1.8 mm, 1.7 mm, 1.6 mm, 1.5 mm, 1.4 mm, 1.3 mm, 1.2 mm, 1.1 mm, 1.0 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, 0.1 mm, or less. Furthermore, it is generally possible for the composite material to be embedded in the substrate as a layer or component of a layer.Further features and their advantages will be evident from the descriptions of the first aspect of the invention, whereby advantageous embodiments of the first aspect of the invention are to be regarded as advantageous embodiments of the second aspect of the invention and vice versa.

[0022] In an advantageous embodiment of the invention, the carrier element comprises at least one material from the group consisting of glass, silicone, plastics, in particular polyacrylate, polymethacrylate, polymethyl methacrylate, polycarbonate, epoxy resin, formaldehyde resin, polyacrylonitrile, polyamides, polybutadiene, polyester, polyethylene, polyurea, polypropene, polystyrene, polyurethane, polyvinyl chloride and / or polytetrafluoroethylene, ceramics, wood, concrete, stone, metal and / or non-metallic hybrid polymer materials. By using a transparent material, the carrier element can be made transparent or at least translucent. By using non-transparent materials such as wood, concrete, stone, steel, metal and the like, conventional building materials can advantageously be coated with the luminescent composite material and configured as a display device according to the invention.This allows, for example, house walls, facades, and similar structures to be retrofitted into display devices according to the invention. In the switched-off or non-excited state of the composite material, these devices are visually inconspicuous and indistinguishable, or at least practically indistinguishable, from unequipped house walls. However, in the switched-on or excited state of the composite material, they are suitable for the potentially large-area presentation of information. Furthermore, by selecting appropriate materials, the display device can be designed to be particularly versatile and can serve, for example, as a window, door, parapet or railing, ceiling or floor element, panel, piece of furniture or part of a piece of furniture, mirror, part of a household appliance, display, head-up display, etc.

[0023] Further advantages arise from the fact that the display device comprises at least two support elements. This allows the display device to be designed with different layer sequences and optimally adapted to various applications. For example, the layer that consists at least partially of the luminescent composite material can be positioned between two support elements to protect the composite material from mechanical damage, environmental influences, etc. The support elements can be, for example, transparent glass and / or plastic sheets, so that the display device can be designed as a transparent double, triple, or multi-layered glazing. Similarly, the display device can comprise a stack of layers consisting of two or more support elements and two or more layers containing composite material.In principle, it is possible for a luminescent composite material and an adjacent support element to be in direct contact or spaced apart. For example, an air gap can be provided between a composite material and a support element. In addition to thermal insulation, this can also improve light transmission into the composite material.

[0024] In a further advantageous embodiment of the invention, the display device comprises at least two layers, which consist at least partially of one or more composite materials according to the first embodiment, wherein the at least two layers are arranged side by side and / or one above the other and / or on opposite sides of a support element and / or on different support elements. This allows the display device to be optimally adapted to its respective application. In particular, by using different composite materials, areas with different emission or excitation wavelengths can be provided, thus offering greater freedom with regard to the possibilities of information presentation. For example, the display device can be designed as a type of display that can show multiple colors.By incorporating a composite material that emits red, green and blue, the display device can, for example, be designed as a type of RGB display.

[0025] In a further embodiment of the invention, at least one quencher and / or absorber is provided, by means of which light of the excitation wavelength(s) and / or emission wavelength(s) of at least one photoluminescent material is absorbed. With the aid of at least one quencher or absorber, certain areas of the display device or the support element can be equipped such that light of the excitation and / or emission wavelength of the respective photoluminescent material is at least partially absorbed. This allows these areas of the display device to appear darker than luminescent areas without a quencher / absorber. Suitable quenchers include, for example, special phosphors that are doped with an activator such that they strongly quench light of certain wavelengths.This means that only certain areas of the display device are capable of emitting light, making it possible to define the light-emitting area with exceptional precision, for example, in the form of a symbol, logo, text, etc. This advantageously eliminates the need for a projector as a light source. Instead, simple light sources such as a widened laser or LEDs are sufficient to present geometrically complex information. In principle, any sufficiently light-absorbing material can be used as an absorber. Furthermore, a transparent substrate can be provided with an absorber or quencher on its side opposite the luminescent layer to prevent light of certain wavelengths from passing through the substrate. Alternatively or additionally, at least one layer can be designed as an antireflective coating.Several advantages can be achieved with the aid of one or more antireflective coatings. When using excitation wavelengths in the deep blue, violet, near-UV, or UV range, and especially when using laser light, it is essential to ensure that reflected or scattered light does not pose a risk of eye damage. An antireflective coating can guarantee the safety of the display device in this regard in a particularly simple manner. It can also prevent potentially disruptive light reflections, thereby improving the viewing angle of the display device. Furthermore, the light propagation in the luminescent layer containing the composite material according to the invention can be selectively influenced by means of a quencher or absorber and / or an antireflective coating.The quencher / absorber can itself be used as a layer or as part of a layer and / or be arranged in the substrate material.

[0026] In a further advantageous embodiment of the invention, the display device comprises means for coupling light into the photoluminescent material and / or at least one controllable and / or adjustable illumination device by means of which the photoluminescent material is excited. This allows for particularly high flexibility with regard to the potentially spatially different excitation of the at least one photoluminescent material. By including means for coupling light into the photoluminescent material, the light propagation can be controlled particularly well, a particularly high luminous efficacy can be achieved, and disruptive light reflections can be at least largely prevented. The coupling can, in principle, take place directly into the luminescent layer containing the composite material and / or into a light-guiding layer that transports the light to the luminescent layer containing the composite material.With the help of a controllable and / or adjustable lighting device, information can be presented particularly easily in a temporal and / or spatially modified way using the display device.

[0027] Further advantages arise from the fact that the lighting device comprises at least one projector and / or at least one laser and / or at least one LED and / or is designed to emit light with different wavelengths. This enables the excitation of the at least one photoluminescent material to be adapted to the specific design and application of the display device. A projector, in particular an (ultra)short-range projector, can be positioned very close to the composite material, allowing for precise control of the light propagation and direction, and preventing unwanted reflections. Furthermore, a projector facilitates time- and location-dependent illumination or excitation of the at least one composite material, enabling the variable presentation of information.The lighting device can generally include one or more filters to filter light of a specific wavelength(s).

[0028] A third aspect of the invention relates to a method for operating a display device according to the second aspect of the invention, in which the composite material arranged as a layer or component of a layer on the support element is exposed to electromagnetic radiation comprising at least one excitation wavelength of the photoluminescent material embedded as a light source in the transparent matrix. Using the method according to the invention, information can be displayed over a large area by exposing the photoluminescent material of the composite material to light, wherein the light contains one or more excitation wavelength(s) suitable for the photoluminescent material. In the simplest case, the light can be sunlight or ambient light; however, one or more artificial light sources can also be provided to excite the at least one photoluminescent material. In the switched-off orIn the non-excited state of the photoluminescent material, at least the composite material according to the invention is essentially transparent and therefore particularly inconspicuous optically. Further features and their advantages will become apparent from the descriptions of the first and second aspects of the invention, whereby advantageous embodiments of the first and second aspects of the invention are to be regarded as advantageous embodiments of the third aspect of the invention and vice versa.

[0029] Additional features of the invention can be found in the claims and the exemplary embodiments. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the exemplary embodiments and / or shown individually, are not only usable in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the exemplary embodiments, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention. Thus, embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed. The following are shown: Fig. 1 a schematic sectional view of an embodiment of a composite material according to the invention; Fig. 2 a schematic sectional view of a first embodiment of a display device according to the invention; Fig. 3 a schematic sectional view of a second embodiment of the display device according to the invention; Fig. 4 a schematic sectional view of a third embodiment of the display device according to the invention; Fig. 5 a schematic sectional view of a fourth embodiment of the display device according to the invention Fig. 6 a schematic perspective view of a further embodiment of the display device according to the invention in the switched-off state; and Fig. 7 a schematic perspective view of the in Fig. 6 shown embodiment of the display device according to the invention in the switched-on state.

[0030] Fig. Figure 1 shows a schematic sectional view of an embodiment of a composite material 10 according to the invention. The composite material 10 comprises a photoluminescent material 12, symbolized by dots, which is embedded as a light source in the form of particles in a transparent matrix 14. The absolute value of the difference of a refractive index n is P of at least one photoluminescent material 12 and a refractive index n M of matrix 14 |n P -n M| = 0.01. By matching the photoluminescent material 12 and the matrix 14 in this way, the composite material 10 is transparent and does not scatter incident light, or at least not substantially. In the illustrated embodiment, the photoluminescent material 12 is a phosphor that, when excited, emits light in the visible spectral range but does not absorb light, or at least not substantially, in the visible spectral range. Therefore, the composite material 10 is not only transparent but also colorless as long as the photoluminescent material 12 is not excited. Thus, when the photoluminescent material 12 is switched off or not excited, the composite material 10 is optically very inconspicuous and cannot be distinguished, for example, from a normal pane of glass or the like. Conversely, when switched on or not excited, the composite material 10 produces light in the visible spectral range.The excited state of the photoluminescent material 12 creates the impression that the light emitted by the photoluminescent material 12 is emitted directly from the supposed "glass pane". This represents a technical solution that differs fundamentally from conventional approaches such as the use of frosted glass or OLEDs, where the luminescent surface has a milky, non-transparent, or yellowish optical appearance when switched off.

[0031] It should be emphasized, however, that non-white photoluminescent materials 12 can also be used if a colored appearance in the unexcited ("off") state is desired or tolerated. Many photoluminescent materials 12, for example, can be excited by blue light (e.g., LED or laser) and therefore have a non-white or colored appearance in the "off" state. For example, a YAG:Ce phosphor has a greenish or yellowish color in the "off" state because it absorbs blue light and emits green or yellow light. The refractive index n P The refractive index of YAG:Ce is approximately 1.83. If such a phosphor is incorporated into a glass, a silicon matrix, or the like with a refractive index n M if, for example, 1.5 is embedded, the general appearance of such a non-inventive composite material in the "off" state is due to the large difference in the refractive indices n P , n Mand the associated strong light scattering makes it milky or opaque, meaning only very limited transparency or even completely opaque.

[0032] Therefore, within the scope of the invention, the matrix 14 is chosen such that it is transparent on the one hand and that, on the other hand, the magnitude of the difference |n P -n M | ≤ 0.2, that means that the refractive index n M of matrix 14 as close as possible to the refractive index n P of the phosphor or photoluminescent material 12. This makes the photoluminescent material 12 almost "invisible" with respect to light scattering, since the phosphor particles do not scatter, or practically do not scatter, the light passing through the composite material 10. Therefore, the transparency of the matrix 14 is maintained, so that the entire composite material 10 is transparent. When a photoluminescent material 12 is embedded in a matrix 14 with at least approximately the same refractive index (n), P ≈ nM The particle size and size distribution of the photoluminescent material 12 usually plays only a minor role.

[0033] To avoid a yellowish or otherwise colored appearance of the composite material 10, it has proven advantageous to use phosphors or photoluminescent materials 12 that do not absorb visible light or absorb it only minimally. For example, phosphors can be used that mainly absorb radiation in the deep blue or violet, near-UV, or UV range, but not or hardly absorb it in the blue, green, yellow, and red regions of the visible spectrum. Some examples of such photoluminescent materials 12 are BaMgAl 10 O 17 :Eu, Mg4GeO 5,5 F:Mn, Sr6BP5O 20 :Eu and Sr4Al 14 O 25 :Eu. By embedding one or more of these photoluminescent materials 12 in a matrix 14 with at least approximately the same refractive index n MThe composite material 10 becomes at least almost completely transparent and colorless. To switch it on or activate it, the photoluminescent material 12 within the composite material 10 can be irradiated with a light source matching the respective absorption wavelengths to cause photoluminescence in the visible spectral range. Depending on the phosphor or phosphor mixture, the resulting light emission lies in different wavelength ranges of the visible spectral range and can be perceived by the human eye.

[0034] In one embodiment, the photoluminescent material 12 emits primary radiation in the red region of the electromagnetic spectrum when excited and consists of a phosphor of the formula (M 1-x EU x ) 10(PO4)6(Cl,F)2, where M = Sr or M = Sr and one or more elements selected from a group comprising Mg, Ca, and Ba. Preferably, x = 0.02–0.08, more preferably, x = 0.03–0.06. Preferably, M contains at least 50 mol% Sr, more preferably at least 70 mol% Sr, and most preferably at least 80 mol% Sr, in each case based on the sum of Mg, Ca, Sr, and Ba.

[0035] Furthermore, the photoluminescent material 12 can be a phosphor of the formula M 1-p EU p (Mg 1-z Mn z )Al 10 O 17where M = Ba or M = Ba and one or more elements selected from a group comprising Mg, Ca, and Sr. Preferably, p = 0.05–0.6 and z = 0.1–0.4; particularly preferably, p = 0.1–0.5 and z = 0.15–0.35. Preferably, M contains at least 50 mol% Ba, particularly preferably at least 70 mol% Ba, and most preferably at least 80 mol% Ba, in each case based on the sum of Mg, Ca, Sr, and Ba.

[0036] In another embodiment, the photoluminescent material 12 emits primary radiation in the red region of the electromagnetic spectrum when excited and consists of a phosphor of formula M 1- y EU y MgAl 10 O 17, where M = Ba or M = Ba and one or more elements selected from a group comprising Mg, Ca, and Sr. Preferably, y = 0.1–0.6, more preferably, y = 0.3–0.6. Preferably, M contains at least 50 mol% Ba, more preferably at least 70 mol% Ba, and most preferably at least 80 mol% Ba, in each case based on the sum of Mg, Ca, Sr, and Ba.

[0037] In another embodiment, the photoluminescent material 12 is a phosphor of the formula M 1-p EU p (Mg 1-z Mn z )Al 10 O 17, where M = Ba or M = Ba and one or more elements selected from a group comprising Mg, Ca, and Sr. Preferably, p = 0.05–0.6 and z = 0.1–0.4; particularly preferably, p = 0.1–0.5 and z = 0.15–0.35. Preferably, M contains at least 50 mol% Ba, particularly preferably at least 70 mol% Ba, and most particularly preferably at least 80 mol% Ba, in each case based on the sum of Mg, Ca, Sr, and Ba.

[0038] In addition to inorganic phosphors, other luminescent materials can also be used as photoluminescent material 12, provided they do not cause excessive light scattering in the composite material 10. Examples of alternative photoluminescent materials 12 are organic dyes or quantum dots, in particular quantum dots with a special core-shell structure that increases the Stokes shift between absorption and emission.

[0039] Typically, an excited photoluminescent material 12 primarily produces one color, that is, mainly blue, green, yellow, or red. The photoluminescent material(s) 12 can therefore be selected such that the composite material 10, when irradiated with light of a suitable excitation wavelength, emits light with a specific spectral emission, e.g., blue, green, yellow, orange, or red. By appropriately selecting the photoluminescent materials 12, the color coordinates of the emitted light can be optimally adjusted to the respective application.

[0040] To generate white light, a mixture of two or more photoluminescent materials 12 can be used, e.g., a blue and a yellow phosphor, or a blue, a green, and a red phosphor. It is also possible to combine several photoluminescent materials 12 in such a way as to obtain white light emission with a color point at or near 2700 K, 3000 K, 4000 K, 5000 K, 6500 K, etc. Accordingly, the color rendering index (CRI) can be adjusted depending on the photoluminescent materials 12 used.

[0041] Depending on the refractive indices n P For the photoluminescent materials 12, it may be necessary to use an individual matrix 14 for each photoluminescent material 12. With identical or at least approximately identical refractive indices n P(± 0.2 or less) of the photoluminescent materials 12, two or more photoluminescent materials 12 can also be embedded in the same matrix 14.

[0042] Common photoluminescent materials 12 typically have a mean grain or particle size in the range of about 0.5 µm to 30 µm. Therefore, they generally scatter light in the wavelength range visible to humans. By using photoluminescent materials 12 consisting of particles whose mean particle diameter is significantly below or above their excitation wavelength, light scattering can be considerably reduced. For example, photoluminescent materials 12 can be used whose mean particle diameter is ≤ 400 nm, in particular < 100 nm and preferably < 5 nm, and / or ≥ 800 nm, in particular > 2 µm, in particular > 10 µm and preferably > 30 µm.

[0043] Matrix 14 can, in principle, comprise or consist of any suitable transparent material. Examples of suitable materials include glass, silicone, plastics, in particular polyacrylate, polymethacrylate, polymethyl methacrylate, polycarbonate, epoxy resin, formaldehyde resin, polyacrylonitrile, polyamides, polybutadiene, polyester, polyethylene, polyurea, polypropene, polystyrene, polyurethane, polyvinyl chloride and / or polytetrafluoroethylene, and / or non-metallic hybrid polymer materials. It is also possible to use a ceramic material as Matrix 14 to obtain a type of fluorescent ceramic that can be produced to be highly transparent and at least largely pore-free. Furthermore, it may be stipulated that the refractive index n M The matrix 14 is fine-tuned by adding one or more filler materials (not shown) and the refractive index n PThe photoluminescent material 12 is approximated as closely as possible. Examples of suitable filler materials are metal oxides such as ZrO2, TiO2, Al2O3, or other suitable materials, which may optionally be nanoscale, in order to avoid light scattering or other optical impairments of the composite material 10.

[0044] Fig. Figure 2 shows a schematic sectional view of a first embodiment of a display device 16 according to the invention. The display device 16 comprises a carrier element 18 on which two layers 20a, 20b are arranged, the layers 20a, 20b each consisting of different composite materials 10a, 10b. The composite materials 10a, 10b comprise different photoluminescent materials 12a, 12b, which are embedded in different matrices 14a, 14b to accommodate the different refractive indices n Pa and n Pbto take this into account and to ensure that the respective differences to the refractive indices n Ma or n Mb The thickness of the matrices 14a, 14b should be at most ±0.2 and preferably at most ±0.01. However, in principle, only one layer 20 may be provided. The support element 18 can be made of a transparent or non-transparent material. For example, the support element 18 can comprise a material from the group consisting of glass, silicone, plastics, in particular polyacrylate, polymethacrylate, polymethyl methacrylate, polycarbonate, epoxy resin, formaldehyde resin, polyacrylonitrile, polyamides, polybutadiene, polyester, polyethylene, polyurea, polypropene, polystyrene, polyurethane, polyvinyl chloride and / or polytetrafluoroethylene, ceramics, wood, concrete, stone, metal and / or non-metallic hybrid polymer materials.

[0045] As an alternative to the illustrated embodiment, further layers can also be provided, which consist at least partially of the composite material 10 according to the invention. Likewise, it can be provided that two or more layers 20a, 20b, etc., are arranged on different sides of the support element 18. Depending on the arrangement of the layers 20a, 20b and the choice of the support element 18, it is therefore possible for the emitted light to have a similar color dot on both sides of the display device 16. This is particularly possible if all photoluminescent materials 12 are embedded in a single layer 20. Likewise, depending on the arrangement of the layers 20a, 20b and the choice of the support element 18, it is possible to emit light with different color dots from both sides of the support element 18. Furthermore, it can also be provided that at least one of the layers 20a, 20b is embedded in the support element 18.

[0046] The layer thickness of each light-emitting layer 20a, 20b or each composite material 10a, 10b can be very small, for example on the order of 1 mm or less. Thus, the light-emitting surface has an essentially two-dimensional shape. The layer thickness can be selected depending on various parameters such as the concentration of the photoluminescent material 12 in the matrix 14 and the absorption cross-section of the composite material 10.

[0047] In addition to facades, the display device 16 can therefore also be used to equip or replace doors, mirrors, windows, etc. It is also possible to design and use such a display device 16 in the form of a glass ceiling, a glass floor, or as a display, in particular as a head-up display. Likewise, the display device 16 can also be used for general lighting, for example, in the form of a window or a lamp that is at least substantially transparent in the "off" state but emits light in the excited or switched-on ("on") state.

[0048] Alternatively, the upper layer 20b can be designed as an antireflective coating. Generally, when using deep blue or violet excitation light, as well as near-UV or UV light, especially laser light, precautions should be taken to prevent eye damage to viewers. To improve the safety of the display device 16, the beam direction can be optimized to avoid reflections. This can be achieved, for example, by using an antireflective coating. Alternatively or additionally, the side of the carrier element 18 opposite layer 20a can be coated with an antireflective coating and / or an absorber to ensure that no light with undesired wavelengths and / or propagation directions can pass through the display device 16.

[0049] Fig. Figure 3 shows a schematic sectional view of a second embodiment of the display device 16 according to the invention. In contrast to the previous embodiment, the display device 16 comprises two support elements 18a, 18b, between which a layer 20 is arranged, consisting of a composite material 10 according to the invention. Due to the layer structure shown, the composite material 10 is particularly well protected against environmental influences. Furthermore, the display device 16 can, for example, be used as a replacement for double glazing. Preferably, at least one of the support elements 18a, 18b consists of a transparent material such as glass, ceramic, silicone, or acrylic glass to allow the transmission of excitation and emission radiation. Alternatively, the excitation radiation can be coupled into the composite material 10 via a light guide (not shown).

[0050] Fig. Figure 4 shows a schematic sectional view of a third embodiment of the display device 16 according to the invention, which, unlike the previous example, is designed as a replacement for triple glazing. For this purpose, the display device 16 comprises three support elements 18a-c, between which two layers 20a, 20b made of respective composite materials 10a, 10b are arranged.

[0051] Fig. Figure 5 shows a schematic sectional view of a fourth embodiment of the display device 16 according to the invention. The structure of the display device 16 essentially corresponds to that shown in Figure 5. Fig. The structure shown in Figure 4 is described. In contrast to the previous embodiment, however, gaps 24 are formed between the composite materials 10a, 10b and the outer support elements 18a, 18c. The gaps 24 can be filled with air, a gas, a predetermined gas mixture, or another suitable material. It is also possible for at least one of the gaps 24 to be evacuated. This enables particularly advantageous light coupling with high quantum efficiency into the central support element 18b, which carries the composite materials 10a, 10b, since coupled light with suitable excitation wavelengths is guided only through the support element 18b. Furthermore, the display device 16 is particularly insensitive to contamination and pressure on the outer support elements 18a, 18c, for example, from a viewer's fingers, with regard to its optical and mechanical properties.

[0052] Fig. Figure 6 shows a schematic perspective view of a further embodiment of the display device 16 according to the invention in the switched-off or non-excited state ("off" state). The display device 16 comprises a transparent carrier element 18 on which a layer 20 is arranged, which consists partly of the composite material 10 according to the invention. Fig. Figure 5 makes it clear that the ability of the display device 16 to display information in the "off" state is not apparent due to the transparency, lack of color and low layer thickness of layer 20.

[0053] Fig. Figure 7 shows a schematic perspective view of the in Fig.Figure 6 shows an embodiment of the display device 16 according to the invention in its switched-on state. It can be seen that the entire layer 20 is illuminated by a lighting device 22 of the display device 16, causing the area of ​​the layer 20 coated with the composite material 10 to photoluminescently emit light of a different wavelength. The display device 16 can therefore function as a type of display by means of a suitable lighting device 22 for stimulating the photoluminescent material(s) 12. The size of the display can be scaled virtually freely by changing the lateral size of the support element 18 or the composite material 10 and the size of the illuminated area. In principle, several lighting devices 22 can also be provided to stimulate different photoluminescent materials 12 and / or to illuminate particularly large layers 20 with stimulating radiation.It is preferably provided that the lighting device 22 generates excitation light that is not or hardly visible to the human eye, so that the excitation light and its origin are not recognizable to an observer.

[0054] By using a projector as a lighting device 22, that is, a light source that can illuminate areas of layer 20 specifically and variably, it is possible to display any logos, texts, animations, etc., so that the display device 16 can be used similarly to a display. The luminance of the light emission can be increased by using a stronger light source or by using several lighting devices 22.

[0055] Furthermore, the illumination device 22 can be positioned very close to the layer 20 by using (ultra)short-throw projectors as a controllable or adjustable light source, which is advantageous with regard to controlling the propagation direction of the excitation light and thus avoiding unwanted reflections. It is also possible to provide some areas of the layer 20 and / or the support element 18 with a quencher and / or absorber that mainly absorbs light and has no photoluminescent properties. In this case, areas can be created that appear dark compared to the areas with embedded or light-accessible photoluminescent material 12. Such a quencher and / or absorber can be a phosphor doped with an activator in such a way that it strongly quenches emission radiation. In this way, only specific areas of the display device 16 or the support element 18 are exposed to light.The layer 20 is capable of emitting light, allowing the light-emitting areas to be defined with particular precision, for example, in the form of a symbol, a logo, text, etc. In this case, a projector is not required as a light source; instead, simpler illumination devices 22, such as an extended laser and / or LEDs, can be used. Instead of such a quencher and / or absorber, it is also possible to use other absorbing materials. It is also possible to leave areas of the support element 18 without a light-emitting layer 20 so that they cannot emit light.

[0056] In general, it is possible to use different types of lighting equipment 22 for stimulation.

[0057] Examples include lasers, LEDs, and conventional light sources, which may optionally be equipped with a filter to block certain wavelength ranges. In addition to irradiation with light, it is possible to couple light into layer 20 or into an adjacent optical fiber layer (not shown). For example, light from a light source can be coupled into an optical fiber from the edges of the support element 18. Alternatively, the support element 18 itself can optionally be used as an optical fiber. If the light is coupled in from the edges of layer 20 and the light intensity is particularly high at the edge, it may be advantageous to form a non-uniform layer 20 on the support element 18 to uniformize the overall light emission over the luminescent area. For this purpose, layer 20 can, for example, have a non-uniform thickness.Alternatively or additionally, the concentration of the photoluminescent material 12 and / or a quencher / absorber can be uneven, for example, lower at the edge and correspondingly higher depending on the distance from the edge, or vice versa. It is also possible to block certain propagation directions of the excitation light and / or the reflected or scattered light by using a suitable material such as glass, plastic, etc., that selectively absorbs the light.

Claims

[1] Composite material (10) comprising at least one photoluminescent material (12) embedded as a light source in a transparent matrix (14) having a refractive index (n P ) of at least one photoluminescent material (12) and a refractive index (n M ) of the matrix (14) have a difference of at most ±0.2, and wherein the photoluminescent material (12) comprises at least one inorganic phosphor from the group - (M 1-x EU x ) 10 (PO4)6(Cl,F)2, in which M is chosen from one or more elements from the group Sr, Mg, Ca and Ba and x = 0.01-0.12; - M 1-y EU y MgAl 10 O 17 , in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr and y = 0.01-0.9; - M 1-z EU z MgAl 10 O 17 , in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr and z = 0.01-0.9; - (M 1-p EU p )6BP5O 20 , in which M is chosen from one or more elements from the group Sr, Mg, Ca and Ba and p = 0.01-0.9; - (Sr 1-q EU q )4Al 14 O 25 , in which q = 0.01-0.9; - Mg4Ge 1-r Mn r (O, F)6, in which r = 0.001-0.06; or - M 1-s EU s (Mg 1-t Mn t )Al 10 O 17 in which M is chosen from one or more elements from the group Ba, Mg, Ca and Sr, s = 0.01-0.7 and t = 0.05-0.

5. [2] Composite material (10) according to claim 1, characterized by , that an absorption maximum of the photoluminescent material (12) lies outside the spectral range visible to humans. [3] Composite material (10) according to claim 1 or 2, characterized by, that the photoluminescent material (12) consists of particles having a mean particle diameter ≤ 400 nm, in particular < 100 nm and preferably < 5 nm, and / or a mean particle diameter ≥ 800 nm, in particular > 10 µm and preferably > 30 µm. [4] Composite material (10) according to any one of claims 1 to 3, characterized by , that the matrix (14) comprises glass, silicone, plastic, in particular polyacrylate, polymethacrylate, polymethyl methacrylate, polycarbonate, epoxy resin, formaldehyde resin, polyacrylonitrile, polyamides, polybutadiene, polyester, polyethylene, polyurea, polypropene, polystyrene, polyurethane, polyvinyl chloride and / or polytetrafluoroethene, ceramic and / or a non-metallic hybrid polymer material. [5] Composite material (10) according to any one of claims 1 to 4, characterized by , that the matrix (14) comprises a filling material by means of which the refractive index (nM) of the matrix (14) is set to a predetermined value. [6] Display device (16) with at least one carrier element (18) comprising at least one composite material (10) according to one of claims 1 to 5 as a layer (20) or component of a layer (20). [7] Display device (16) according to claim 6, characterized by , that the support element (18) comprises at least one material from the group consisting of glass, silicone, plastics, in particular polyacrylate, polymethacrylate, polymethyl methacrylate, polycarbonate, epoxy resin, formaldehyde resin, polyacrylonitrile, polyamides, polybutadiene, polyester, polyethylene, polyurea, polypropene, polystyrene, polyurethane, polyvinyl chloride and / or polytetrafluoroethene, ceramics, wood, concrete, stone, metal and / or non-metallic hybrid polymeric materials. [8] Display device (16) according to claim 6 or 7, characterized by that it comprises at least two support elements (18a, 18b). [9] Display device (16) according to any one of claims 6 to 8, characterized by, that these comprise at least two layers (20a, 20b) which consist at least partially of one or more composite materials (10) according to one of claims 1 to 7, wherein the at least two layers (20a, 20b) are arranged next to each other and / or one above the other and / or on opposite sides of the support element (18) and / or on the different support elements (18a, 18b). [10] Display device (16) according to any one of claims 6 to 9, characterized by , that at least one quencher and / or absorber is provided, by means of which light of the excitation wavelength(s) and / or emission wavelength(s) of at least one photoluminescent material (12) is to be absorbed, and / or that at least one layer (20) is designed as an antireflection coating. [11] Display device (16) according to any one of claims 6 to 10, characterized by, that this means for coupling light into the photoluminescent material (12) and / or at least a controllable and / or adjustable lighting device (22) by means of which the photoluminescent material (12) is to be excited. [12] Display device (16) according to claim 11, characterized by , that the lighting device (22) comprises at least one projector and / or at least one laser and / or at least one LED and / or is designed to emit light of different wavelengths. [13] Method for operating a display device (16) according to one of claims 6 to 12, in which the composite material (10) arranged as a layer (20) or part of a layer (20) on the support element (18) is subjected to electromagnetic radiation comprising at least one excitation wavelength of the photoluminescent material (12) embedded as a luminescent medium in the transparent matrix (14).

Images