Lightning facility

Abstract

To provide a lightning facility which includes a primary light source and a light conversion element for receiving primary light and discharging secondary light with a wavelength different from that of the primary light.SOLUTION: A lightning facility includes a light source for discharging primary light and a light conversion unit. The light conversion unit is made of a light conversion element having a front surface and a back surface or includes the light conversion element. The light conversion element is irradiated with primary light in the front surface and discharges secondary light with a different wavelength from that of the primary light from the front surface. The light conversion element has a first phase including a light conversion ceramic material and a second phase including an additional ceramic material. The second phase has higher thermal conductivity than the first phase and the optical conversion element includes a plurality of small holes.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a lighting facility including a primary light source and a light conversion element that is irradiated with the primary light and emits secondary light having a changed wavelength relative to the primary light.

[0002] Light conversion elements, especially ceramic converters, usually contain a specific material as a light emitter, for example Ce-doped yttrium aluminum garnet (YAG) or Ce-doped ruthenium aluminum garnet (LuAG). The specific light emitter determines, among other things, the absorption and emission spectra, which in turn affect the thermal conductivity of the light conversion element.

[0003] The thermal conductivity of the converter material affects how high the excitation light power can be and how bright the excitation light can be before the emitter temperature becomes too high, causing a decrease in quantum efficiency and preventing further increases in light output or brightness, i.e., an irradiance limit is reached.

[0004] The thermal conductivity of the widely used and described Ce-doped garnet ceramics is in the range of approximately 5-10 W / mK (at room temperature), depending on the exact composition, which is already relatively high compared to other oxides (many oxides, or even glasses, have thermal conductivities in the range of only 1-2 W / mK).

[0005] However, there are oxides that have significantly higher thermal conductivities than garnets, such as Al2O3 (especially corundum) at about 30 W / mK, MgO (magnesia) at about 40 W / mK, or BeO at about 300 W / mK. It should be noted that these literature values ​​refer to single crystal materials, whereas values ​​for ceramic structures can be significantly lower.

[0006] When materials having higher thermal conductivity than Ce-doped garnets are combined with them to form a mixed ceramic, the mixed ceramic may be capable of significantly higher "irradiance" or significantly higher "light output" under certain conditions than a similar ceramic of the same dimensions but in a single phase under the same conditions.

[0007] The use of mixed ceramics in converter elements is generally known from literature and patent applications, sometimes described in terms of specific converter materials having specific volume fractions of converter ceramics, grain sizes, grain shapes, grain boundary lengths, etc.

[0008] However, the existing literature is generally directed to designing for transparency in applications, for example in the field of LED lighting.

[0009] In contrast, the present invention is based on the task of utilizing the advantages of mixed ceramics for efficient lighting fixtures with a reflective design.

[0010] For this purpose, the invention discloses a lighting installation comprising a light source for emitting primary light, in particular formed as a laser or a light-emitting diode, preferably formed as a laser, and a light conversion unit.

[0011] The light-conversion unit is formed by or comprises a light-conversion element having a front surface and a rear surface, the light-conversion element being designed such that primary light is irradiated onto its front surface and secondary light having a changed wavelength relative to the primary light is emitted from its front surface.

[0012] Optionally, the light-converting unit further comprises a substrate which is directly or indirectly bonded to the rear surface of the light-converting element and which is advantageously formed as a heat sink.

[0013] Advantageously, the substrate consists entirely or for the most part of a material having a thermal conductivity of more than 30 W / mK, advantageously more than 100 W / mK, even more preferably more than 150 W / mK, even more preferably more than 350 W / mK, and / or comprises at least one ceramic and / or at least one metal and / or at least one ceramic-metal composite. Particularly preferably, the substrate comprises at least one metal, advantageously selected from Cu, Al, Fe or Ni, in particular Cu, for example Ni-P-coated and / or Au-coated Cu.

[0014] Optionally, the light-conversion unit further comprises an adhesive, which is located between the light-conversion element and the substrate and is preferably formed as an organic adhesive, a glass, a ceramic adhesive, an inorganic adhesive, a sintered sintered paste and / or a metal solder joint, preferably as a metal solder joint or a sintered sintered paste, preferably as a metal solder joint.

[0015] The light-converting element comprises a first phase comprising a light-converting ceramic material and a second phase comprising a further ceramic material, the second phase having a higher thermal conductivity than the first phase.

[0016] Furthermore, the light-converting element comprises a plurality of pores, which serve, among other things, to scatter the light.

[0017] The degree of light scattering (scattering coefficient) (together with the absorption coefficient) influences, among other things, how large the proportion of converted, backscattered, especially blue, excitation radiation is, and how much the excitation radiation diffuses within the converter before it is completely absorbed, and how much the converted light diffuses within the converter before it leaves the converter as useful light again. Important characteristics such as the efficiency of the component and the size of the emitting spot are influenced by scattering. For reflective (illumination and emission take place in the same plane) luminaires, a sufficiently large light scattering coefficient is the aim.

[0018] A light-converting element containing a large number of pores advantageously allows for increased light scattering in the light-converting element. This allows particularly mixed ceramics to be used efficiently in reflective modes, such as for example SSL (solid-state lighting). In particular, for mixed ceramics with phases that have a small change in refractive index, the increased scattering due to the pores is particularly advantageous. For example, the refractive index of Al2O3 is about 1.77, which is only slightly lower than that of YAG (about 1.83). Therefore, the light scattering effect of the mixed ceramic alone is low, and the light scattering effect is significantly increased by the pores.

[0019] In contrast, in known, especially transmissive lighting, porosity is usually intentionally suppressed, sometimes by processes such as hot isostatic pressing (HIP) or "spark plasma sintering" to achieve high-density ceramics. In the case of transmissive geometries, the additional heterogeneous components may already be sufficient to cause less light scattering than in reflective lighting fixtures.

[0020] Optionally, the light-converting unit comprises at least one highly reflective coating, which is preferably a metallic coating and / or a metal-containing coating and / or a dielectric coating, particularly preferably an Ag coating or an Ag-containing coating.For example, it can be provided that the light-converting element has a mirror film on its backside, which is particularly metallic, preferably has Ag or consists of Ag, and this is particularly performed in such a way that the backside of the light-converting element is coated with a mirror film, which is preferably applied to the backside of the light-converting element by vapor deposition, sputtering (thin film) or printing (thick film).

[0021] In one embodiment, the light conversion element has a mirror film which is a thin film. Advantageously, the thin film comprises or consists of Ag and / or has a thickness of 50 nm to 500 nm, preferably 100 nm to 350 nm, more preferably 125 nm to 300 nm, particularly preferably 150 nm to 250 nm. In some embodiments, the light conversion element has a thin film comprising or consisting of Ag and a further thin film comprising or consisting of Au. Advantageously, the further thin film is applied by vapor deposition or sputtering. Advantageously, the thin film comprising or consisting of Au has a thickness of 50 nm to 500 nm, preferably 100 nm to 350 nm, more preferably 125 nm to 300 nm, particularly preferably 150 nm to 250 nm. The thin film comprising or consisting of Au can serve to protect the mirror film comprising or consisting of Ag from oxidation reactions which may occur, especially at high temperatures, for example, when the light conversion element is bonded to a substrate, for example with a sintering paste.

[0022] In one embodiment, the light conversion element has a mirror film which is an Ag-containing thick film. Advantageously, the thick film has a thickness of 1 μm to 25 μm, preferably 5 μm to 20 μm, particularly preferably 10 μm to 15 μm.

[0023] Alternatively or additionally, the rear surface of the light-converting element may be mirror-finished with a dielectric film system that is specifically optimized for maximum reflectivity.

[0024] The dielectric film system may advantageously be sealed on the outside with a metallic mirror film, so that the order of the films is converter element - dielectric film system - metallic mirror film.

[0025] Instead of or in addition to applying a highly reflective coating to the rear surface of the light-converting element, the rear surface of the light-converting element may be bonded to a mirror body, preferably an Ag mirror or a silver-plated substrate, the mirror body being preferably formed by or applied to the substrate.

[0026] It can be provided that the light conversion unit comprises at least one optical isolation film, which is advantageously located between the at least one highly reflective film and the rear surface of the light conversion element, the at least one optical isolation film advantageously being transparent and / or having a refractive index lower than the refractive index of the light conversion element, and the at least one optical isolation film advantageously comprising or consisting of SiO2.

[0027] The optical separation film advantageously has a thickness of less than or equal to 5 μm, preferably less than or equal to 3 μm, preferably in the range from 0.5 to 1.5 μm, particularly preferably in the range from 0.8 to 1.2 μm. The optical separation film can serve to separate the reflection and possibly total reflection at the converter back surface of the secondary light reaching the converter back surface from the reflection at a highly reflective film, in particular a metallic mirror, of the part of the secondary light passing through the converter back surface.

[0028] It can be provided that between the at least one highly reflective film, preferably a metal or metal-containing coating, and the optical separation film, there is a transparent adhesion-promoting film, which advantageously comprises or consists of one or more oxides selected from the group consisting of SnO2, TiO2, Y2O3 and La2O3, preferably Y2O3. Advantageously, the adhesion-promoting film has a thickness of 1 nm or more and / or less than 100 nm, preferably less than 75 nm, further preferably less than 50 nm, preferably less than 35 nm, particularly preferably less than 20 nm.

[0029] The optional bonding material may be at least one organic adhesive, at least one glass, at least one ceramic adhesive, at least one inorganic adhesive, at least one sintered sinter paste, and / or at least one metal solder bonding material.

[0030] The adhesive can in particular be formed as a bonding film.

[0031] In a preferred embodiment, the bonding film is formed from at least one adhesive. Suitable adhesives are organic adhesives having properties suitable for the specific application and the specific structure of the respective converter, for example with regard to heat resistance, thermal conductivity, transparency and curing behavior.

[0032] In a preferred embodiment, this is filled and unfilled epoxy resins and silicones. The adhesive system bonding film typically has a thickness of 5 to 70 μm, preferably 10 to 60 μm, more preferably 20 to 50 μm, particularly preferably 30 to 50 μm.

[0033] In a further preferred embodiment, the bonding film is glass, preferably selected from solder glass or thin glass.

[0034] Solder glasses are in particular special glasses with a relatively low softening temperature of 750° C. or less, preferably 560° C. or less. In principle, glass solders can be used in various forms, for example as powders, as pastes in liquid media or embedded in a matrix that is applied to the converter substrate or converter components. Application can take place by strand application, by screen printing, by spraying or in the form of loose powder. The individual components of the converter are then assembled.

[0035] In a preferred embodiment, a paste containing a glass powder is used, for example a paste containing a PbO-, Bi2O3-, ZnO-, SO3-, B2O3- or silicate-based glass, particularly preferably a silicate-based glass.

[0036] Thin glass in the sense of the present application is thin glass having a maximum thickness of less than or equal to 50 μm and a softening temperature of less than or equal to 750° C., preferably less than or equal to 560° C. Such glass can be placed between the converter component and the converter substrate and compressed at a sufficiently high temperature and at a sufficiently high pressure. Suitable thin glasses are in particular borosilicate glasses, for example available under the trademark D263 from the company SCHOTT.

[0037] The glass-based bonding film has a thickness of, for example, 15 to 70 μm, preferably 20 to 60 μm, and particularly preferably 30 to 50 μm.

[0038] In another embodiment, the light conversion element is bonded to the substrate by a ceramic adhesive.

[0039] Such ceramic adhesives are typically substantially free of organic components and exhibit high heat resistance. Preferably, the ceramic adhesive is selected such that the thermal expansion coefficient and mechanical properties, e.g., Young's modulus, of the resulting bonded film match the corresponding properties of the substrate and / or converter.

[0040] Suitable ceramic adhesives are produced, for example, from inorganic, preferably powdered, solids and a liquid medium, preferably water. The inorganic solids may be, for example, MgO-, SiO2-, TiO2-, ZrO2- and / or Al2O3-based solids. Preferably, the inorganic solids are SiO2- and / or Al2O3-based solids, particularly preferably Al2O3-based solids. The powdered solids may further comprise further powdered components, for example, which aid in the curing of the ceramic adhesive. Such components may be, for example, boric acid, borates or alkali metal silicates, such as sodium silicate.

[0041] Ceramic adhesives, for example, can be mixed from powdered solids and water immediately prior to use and allowed to cure at room temperature.

[0042] In this case, the solid preferably has an average particle size d50 of 1 to 100 μm, preferably 10 to 50 μm. -6 1 / K, particularly preferably 6 to 10×10 -6 It has a coefficient of thermal expansion of 1 / K. Suitable ceramic adhesives are, for example, manufactured by Resbond 920 or Resbond 940 HT (Polytec PT GmbH).

[0043] The ceramic adhesive bonding film has a thickness of, for example, 50 to 500 μm, preferably 100 to 350 μm, and particularly preferably 150 to 300 μm.

[0044] In an advantageous embodiment, the joining material is a metal solder, advantageously a metal solder containing an alloy of two or more metals. Suitable metal solder joining materials have a melting point lower than the melting and / or decomposition points of the individual components of the light-conversion unit and / or higher than the maximum temperature reached during operation of the light-conversion element in contact with the solder. The melting point of the metal solder joining material is preferably 150°C to 450°C, more preferably 180°C to 320°C, particularly preferably 200 to 300°C. Suitable metal solder joining materials are, for example, silver solder and gold solder, preferably Ag / Sn solder, Ag / Au solder and Au / Sn solder, particularly preferably Au / Sn solder, for example AuSn8020.

[0045] The bonding material can be in the form of a sintered paste, preferably an Ag-containing sintered paste.

[0046] Advantageously, the sintered sinter-type paste has a film thickness of 1 μm to 50 μm, advantageously 5 μm to 40 μm, preferably 10 μm to 30 μm, particularly preferably 15 μm to 25 μm.

[0047] Advantageously, the sintered sinter-type paste has a thermal conductivity of at least 50 W / mK, preferably at least 100 W / mK, particularly preferably at least 150 W / mK.

[0048] In particular, in the embodiment in which the bonding material is a sintered sintered paste, it is advantageous for the surface of the light conversion element and the surface of the substrate to be bonded together to have a coating. Advantageously, the light conversion element has an Ag-containing thin film, optionally further an Au-containing thin film, or is coated with a Cu-containing thin film or an Ag-containing thick film. Preferred embodiments of the Ag-containing and Au-containing thin films and Ag-containing thick films have been described above and apply here as well. In an advantageous embodiment, the surface of the substrate has a coating, which is advantageously an Au-containing coating and / or a NiP coating. Advantageously, the surface of the substrate has a NiP film, which advantageously has a thickness of 1 μm to 10 μm, advantageously 3 μm to 7 μm, and / or the Au film advantageously has a thickness of 50 nm to 500 nm, advantageously 100 nm to 400 nm, preferably 150 nm to 300 nm.

[0049] In an embodiment in which the bonding material is a sintered paste, the bonding between the light conversion element and the substrate is carried out by the following steps: a) providing a substrate and a light conversion element; b) applying a sinterable paste to at least a portion of the surface of the substrate and / or to at least a portion of the surface of the light-converting element; c) contacting a surface of a substrate with a surface of a light-converting element, whereby at least a portion of the surface of the substrate and / or at least a portion of the surface of the light-converting element is covered with the sinter-type paste; d) sintering the bonded body obtained in step c).

[0050] In step a) of the method a substrate and a light-converting element are provided. Advantageously, the surface of the substrate and / or the light-converting element has a coating as detailed above.

[0051] In step b), the sintering paste is applied to at least a portion of the surface of the substrate and / or to at least a portion of the surface of the light conversion element. Advantageously, the sintering paste is applied to at least a portion of the substrate. Typically, this amount of sintering paste is applied such that after the sintering step d), the sintered sintering paste has a film thickness of 1 μm to 50 μm, advantageously 5 μm to 40 μm, particularly preferably 10 μm to 30 μm, particularly preferably 15 μm to 25 μm.

[0052] In step c), the surface of the substrate and the surface of the light-converting element are brought into contact with each other, with at least a portion of the surface of the substrate and / or at least a portion of the surface of the light-converting element being covered with a sintering paste. Advantageously, the surface of the light-converting element and a portion of the surface of the substrate are brought into contact, with at least a portion of the surface of the substrate being covered with a sintering paste. Advantageously, this contact is effected with a force of preferably at least 15 mN / mm 2 , preferably 30 mN / mm 2 More than 60 mN / mm 2 This is done using pressure of up to 10 ...

[0053] In step d), the bonded body obtained in step d) is sintered. Sintering can be carried out in an oxygen-containing atmosphere, or in air, or in a protective gas atmosphere, in particular in an N2 or Ar atmosphere. Sintering is carried out at a temperature in the range of 180°C to 300°C.

[0054] Advantageously, the sintering paste has a sintering temperature of 300° C. or less, advantageously 280° C. or less, preferably 250° C. or less. Advantageously, sintering is carried out by heating the joint body to the desired sintering temperature, advantageously in a first stage to the first temperature, advantageously at least 0.5 K / min, preferably at least 0.75 K / min and / or at most 3 K / min, preferably at most 2 K / min. Advantageously, the first temperature is in the range of 70° C. to 120° C., advantageously 80° C. to 105° C. Advantageously, after reaching the first temperature, the temperature is held for 1 min to 60 min, advantageously 5 min to 45 min, preferably 20 min to 40 min. Advantageously, the joint body is then heated in a second stage to the second temperature, advantageously at least 1.0 K / min, advantageously at least 1.5 K / min and / or at most 3.5 K / min, preferably at most 3 K / min. Advantageously, the second temperature is in the range of 180° C. to 300° C., advantageously 200° C. to 280° C., which corresponds to the sintering temperature. Advantageously, after reaching the second temperature, i.e. the sintering temperature, the temperature is maintained for at least 10 minutes, preferably at least 20 minutes or at least 30 minutes and / or up to 60 minutes, preferably up to 50 minutes or 40 minutes. Cooling of the bonded body is then carried out, advantageously to room temperature.

[0055] In an embodiment in which the rear surface of the light conversion element is bonded to a mirror body, advantageously an Ag mirror body or a silver-plated substrate, the mirror body being advantageously formed by or applied to the substrate, it can be provided that an adhesive is present between the mirror body or the mirror-finished substrate and the light conversion element, the adhesive advantageously comprising or consisting of an optically transparent organic or inorganic adhesive and / or consisting of a transparent material having a refractive index lower than that of the light conversion element, preferably comprising an optically transparent organic adhesive having a refractive index lower than that of the light conversion element, the adhesive advantageously having a thickness in the range of less than 30 μm, preferably in the range of 10 to 20 μm.

[0056] It can be provided that a part or the whole of the surface of the light-converting element facing the incident light is provided with a single-layer or multi-layer anti-reflection coating.

[0057] In a preferred embodiment of the invention, the light-converting element has a porosity, in particular in terms of the pore volume relative to the total volume of the light-converting element, of at least 0.5%, advantageously at least 1.5%, particularly preferably at least 3% and even more preferably between 3% and 7%.

[0058] Alternatively or additionally, the light-converting element may have at least 200 pores per square millimeter, advantageously at least 300 pores per square millimeter, particularly preferably at least 400 pores per square millimeter, in cross section.

[0059] The cross section of the light conversion element can be examined, in particular, by scanning electron microscopy (SEM). Such a cross section of the light conversion element may further be polished. In that case, in particular, polished pores may be visible on the polished cross section (polished surface), which may further be visible, in particular, by SEM. For example, 2 A cross section of the area can be observed and evaluated.

[0060] In particular, for example, 61800 μm 2 For a cross section with an area of ​​1 cm 2 At least 20,000 pores per cm, preferably 2 At least 30,000 pores per cm 2 Alternatively or additionally, there may be at least 40,000 pores per cm. 2 20,000 to 200,000 pores per cm, preferably 2 30,000 to 150,000 pores per cm, particularly preferably 1 cm 2 There may be 40,000 to 120,000 pores per well.

[0061] The diameter of the pores, in particular the median diameter of the pores present in the cross section, may be between 100 nm and 3000 nm, advantageously between 300 nm and 1500 nm, particularly preferably between 400 nm and 1200 nm.

[0062] The median divides a data set, sample or distribution, in this case for example the diameter of the pores or the diameter of the crystallites present in a cross section, in half such that one half has values, i.e. pore diameters, less than or equal to the median and the other half has values ​​greater than or equal to the median.

[0063] The first phase of the light conversion element can comprise a plurality of crystallites, the median diameter of which is advantageously between 300 nm and 5000 nm, particularly preferably between 500 nm and 3000 nm.

[0064] The second phase of the light conversion element can comprise a plurality of crystallites, the median diameter of which is advantageously between 300 nm and 5000 nm, particularly preferably between 500 nm and 3000 nm.

[0065] It can be provided that the ratio of the median diameter of the pores, in particular the pores present in the cross section, to the median diameter of the crystallites of the first phase and / or the second phase, in particular the crystallites of the first phase and / or the second phase present in the cross section, is 0.02 to 10, advantageously 0.06 to 5, particularly preferably 0.13 to 2.4.

[0066] It can furthermore be provided that the pores, in particular the pores present in the cross section, advantageously at least 1%, preferably at least 5%, are contained in the first phase such that these pores are only bordered by the material of the first phase.

[0067] The pores, in particular advantageously at least 1%, preferably at least 5% of the pores present in the cross section, may be contained in the second phase such that these pores are only bordered by the material of the second phase.

[0068] Advantageously at least 1%, preferably at least 5%, of the pores present in the cross section may be located between the first and second phase such that these pores border both the first and second phase materials.

[0069] The percentage values ​​indicated in particular each represent the number of particular pores determined in the cross section relative to the total number of pores determined in the cross section.

[0070] Preferably, the pores are produced during the sintering process, advantageously without the use of pore formers, and the pores are not subsequently introduced, in particular by, for example, selective etching.

[0071] The porosity, in particular in the cross section, in particular the number of pores per square millimeter in the cross section and / or the median diameter of the pores, in particular in the cross section, is advantageously designed to be uniform in the light-converting element and / or is the same on the surface of the light-converting element as in the internal cross section of the light-converting element or differs from the internal cross section of the light-converting element by at most 10%.

[0072] The first phase of the light conversion element has a refractive index of 1.8 or more, particularly 1.8 to 1.9, at 500 nm.

[0073] The second phase of the light conversion element has a refractive index of 1.8 or less, particularly 1.7 to 1.8, at 500 nm.

[0074] Advantageously, the refractive index of the first phase of the light-transforming element at 500 nm is the same as or higher than the refractive index of the second phase of the light-transforming element at 500 nm. Advantageously, the difference between the refractive index of the first phase of the light-transforming element at 500 nm and the refractive index of the second phase of the light-transforming element at 500 nm is 0.15 or less, preferably 0.1 or less, particularly preferably 0.7 or less, and even more preferably 0.5 or less.

[0075] The refractive index of the first phase of the light conversion element and the refractive index of the second phase of the light conversion element can be determined, for example, using ellipsometry on double-sided polished samples of known thickness of each material.

[0076] In one embodiment of the present invention, the scattering coefficient of the light conversion element at a wavelength of 600 nm is 150 cm -1 Larger, preferably 300cm -1Larger, particularly preferably 300 cm -1 ~1200 cm -1 is.

[0077] The scattering coefficient is determined by fitting the model described in V. Hagemann, A. Seidl, G. Weidmann: Static ceramic phosphor assemblies for high power high luminance SSL-light sources for digital projection and specialty lighting, Proc. of SPIE Vol. 11302 113021N-11, SPIE OPTO, San Francisco 2020 to the measured value of backscattering at 600 nm.

[0078] In one embodiment of the present invention, the first phase can be described as composition (A 1-y R y )3B5O 12 , where A includes one or more elements from the group of lanthanoids and Y, R includes one or more elements from the group of lanthanoids, B includes one or more elements from the group of Al, Ga, In, y represents the ratio of R atoms at the A site of the crystal lattice, and 0 < y < 0.02, preferably 0 < y < 0.012, particularly preferably 0.001 < y < 0.009 holds.

[0079] In the above embodiment, A may be composed of one or more of the elements Y, Gd, Lu, and / or B may be composed of one or more of the elements Al, Ga, In.

[0080] In one embodiment of the present invention, it is provided that the second phase of the light conversion element contains or consists of aluminum oxide.

[0081] Regarding the volume fraction z of the second phase, the following can hold: 0.05 < z < 0.95, preferably 0.3 < z < 0.7, particularly preferably 0.45 < z < 0.7.

[0082] In one embodiment, the light conversion element is a system [(Y 1-y Ce y )3AlO 12 ] 1-z [Al2O3] z , [(Lu 1-y Ce y )3AlO 12 ] 1-z [Al2O3] z , [(Y 1-x-y Gd x Ce y )3AlO 12 ] 1-z [Al2O3] z , [(Lu 1-y Ce y )3(Al 1-w Ga w )3O 12 ] 1-z [Al2O3] z In particular, 0 <x<0.2であり、かつ0<w<0.3である。

[0083] It can be provided that the thermal conductivity of the light-converting element is greater than 10 W / mK, preferably greater than 12 W / mK, particularly preferably greater than 14 W / mK at room temperature.

[0084] The present invention further relates to a light-converting unit formed by or comprising a light-converting element having a front surface and a rear surface, the light-converting element being designed such that when primary light is irradiated onto its front surface, secondary light having a changed wavelength relative to the primary light is emitted at its front surface.

[0085] The light-converting unit optionally comprises a substrate which is directly or indirectly bonded to the rear surface of the light-converting element and is preferably formed as a heat sink, and optionally a bonding material which is located between the light-converting element and the substrate and is preferably formed as an organic adhesive, a glass, a ceramic adhesive, an inorganic adhesive, a sintered sintered paste and / or a metal solder bonding material, preferably as a metal solder bonding material or a sintered sintered paste, preferably as a metal solder bonding material.

[0086] The light-converting element comprises a first phase comprising a light-converting ceramic material and a second phase comprising a further ceramic material, the second phase having a higher thermal conductivity than the first phase.

[0087] The light-converting element comprises a plurality of pores, which serve inter alia to scatter the light.

[0088] The lighting fixtures or light conversion units described above can for example be used in "dynamic" applications (color wheels) or in "static" applications (die on heat sink).

[0089] The invention will now be described in more detail with reference to the accompanying drawings. [Brief description of the drawings]

[0090] [Figure 1] FIG. 1 shows experimentally determined reflectance spectra of converter ceramics with and without Al2O3 addition at various porosities. [Diagram 2] FIG. 13 shows the scattering coefficient calculated from reflectance measurements for converter ceramics with and without Al2O3 addition at various porosities. [Diagram 3] FIG. 1 shows an SEM image of a mixed ceramic with composition [(Y0.993Ce0.007)3Al5O12]0.46[Al2O3]0.54, showing light phase: YAG, dark phase: Al2O3 and pores. [Figure 4] FIG. 2 shows the thermal conductivity at 20° C. of the materials in Table 2. (At this order of porosity, the thermal conductivity decreases linearly with increasing porosity, and the mixed ceramics exhibit significantly higher thermal conductivity than the pure phase YAG ceramics.) [Diagram 5] FIG. 1 shows an SEM image of a mixed ceramic of composition [(Y0.989Ce0.011)3Al5O12]0.65[Al2O3]0.35, showing the light phase: (Y0.989Ce0.011)3Al5O12, the dark phase: Al2O3, and some visible pores (completely dark) are exemplarily marked. [Figure 6] FIG. 1 shows an SEM image of a mixed ceramic with the composition [(Lu0.9937Ce0.008)3Al5O12]0.5[Al2O3]0.5. [Figure 7] FIG. 1 shows an SEM image of a mixed ceramic of composition [(Lu0.9937Ce0.008)3Al5O12]0.5[Al2O3]0.5, showing the presence of visible pores (completely dark), light phase: (Lu0.9937Ce0.008)3Al5O12, dark phase: Al2O3. [Figure 8] FIG. 1 shows the scattering coefficients calculated from reflectance measurements for the converter ceramics of Table 3. [Figure 9] FIG. 1 shows the distribution of pore diameters in nm on a cross section (polished surface).

[0091] For efficient reflective lighting installations with light conversion elements containing mixed ceramics, especially for SSL (Solid State Lighting), the pores allow a sufficiently large scattering (sufficiently large scattering coefficient). This applies in particular to the materials Al2O3 and YAG.

[0092] There is no significant difference between the refractive index of Al2O3 and that of YAG, with the refractive index of Al2O3 being approximately 1.77 and that of YAG being approximately 1.83. Therefore, it can be estimated that the light scattering effect of the mixed ceramic alone is relatively low if there are no pores.

[0093] This has been experimentally proven in an original study: Converter ceramics with different porosity (and therefore different scattering properties) were fabricated from Ce:LuAG, some without the addition of Al2O3 and some with the addition of aluminum oxide (here Lu3Al5O 12 From the theoretical density ρ1 (of Al2O3) and ρ2 (of Al2O3 here) and the weights m1 and m2, the theoretical density ρ th is determined:

number

[0094] The density ρ of the produced sintered body is measured, from which the porosity P of the sintered body is obtained:

number

[0095] Samples of a certain thickness (both sides polished) in the range of 100-250 μm were prepared from sintered bodies with different porosities. The reflectance was measured in the green to red spectral range (because absorption is negligible here). The reflectance thus determined includes both Fresnel reflection and back scattering.

[0096] The model described in V. Hagemann, A. Seidl, G. Weidmann: Static ceramic phosphor assemblies for high power high luminance SSL-light sources for digital projection and specialty lighting. Proc. of SPIE Vol. 11302 113021N-11, SPIE OPTO, San Francisco 2020 was applied.

[0097] The above model can be used to simulate these experimental conditions. Since the absorption in this spectral range is negligible, the reflected intensity depends on the refractive index of the double-polished platelet, its thickness and the scattering coefficient. Since the (possibly average) refractive index and thickness are known, it is possible to calculate the scattering coefficient from such measurements.

[0098] FIG. 1 shows the reflectance spectra of nine exemplary samples measured in this manner.

[0099] Table 1 summarizes the measurement and simulation results.

[0100] [Table 1]

[0101] Figure 2 shows that in the measured materials the scattering coefficient increases almost linearly with the porosity, which is also expected (the scattering coefficient is always proportional to the number of scattering centers), but what is particularly important is that even with a very high percentage of Al2O3 the material does not scatter significantly more than a material without Al2O3.

[0102] In a reflective geometry where the light strikes the front surface of the light conversion element and the secondary light is also emitted from this front surface, the distance is about 150 to about 1200 cm, depending on the application. -1 To achieve such a scattering coefficient, a porosity of at least 1% is advantageously provided, notwithstanding the presence of Al2O3 in the material.

[0103] The reflective lighting device in particular has a mixed ceramic containing pores. In other words, the mixed ceramic can be produced as a porous mixed ceramic. Advantageously, this allows the scattering coefficient to be increased to 150 cm -1 ~1200cm -1 Advantageously, the second of the light-converting elements can comprise Al2O3.

[0104] The production of such porous mixed ceramics can be carried out in various ways.

[0105] One method involves mixing powders of pure oxides of yttrium oxide, lutetium oxide, aluminum oxide, gallium oxide, gadolinium oxide and cerium oxide according to the desired composition and stoichiometry. The aluminum oxide added in "stoichiometric excess" will be the Al2O3 phase in the matrix, and the rest will be the respective desired garnet phase. After adding ethanol (or water, or other fluid), dispersion aids and pressing aids, grinding balls are added to the slurry and it is pulverized in a barrel using a roller platform. The slurry is then dried and then compressed to form a green body. The green body is debindered at a temperature above about 500°C, and then reactively sintered in air, oxygen or even vacuum at a sufficiently high temperature above about 1400°C until the desired density or porosity is reached. If the porosity is still too high, one or more additional sinterings can be continued until the target value is reached.

[0106] Another method is to mix a powder of pre-synthesized garnet of the desired composition with Al2O3 powder. If the garnet powder does not already contain Ce, cerium oxide powder can also be added in the desired amount. After adding ethanol (or water, or other fluid), dispersion aids, and pressing aids, grinding balls are added to the slurry and it is pulverized in a barrel using a roller platform. The slurry is then dried and then compressed to form a green body. The green body is debindered at a temperature above about 500°C, and then reactively sintered in air, oxygen, or even in vacuum at a sufficiently high temperature above 1400°C until the desired density or porosity is reached. If the porosity is still too high, one or more additional sinterings can be continued until the target value is reached.

[0107] This is [(A 1-y R y )3B5O 12 ] 1-z [Al2O3] zIt can be carried out for all compositions according to the notation, where A contains one or more elements of the group of lanthanoids and Y, R contains one or more elements of the group of lanthanoids, B contains one or more elements of the group of Al, Ga, In, y represents the proportion of R atoms at the A site of the crystal lattice, z represents the volume fraction of Al2O3 in the solid of the ceramic matrix (i.e., when pores are not considered), 0 < y < 0.02, and 0.05 < z < 0.95.

[0108] Preferably, A is one or more elements of Y, Gd, Lu, B is one or more elements of Al, Ga, 0 < y < 0.012, and 0.3 < z < 0.7.

[0109] System [(Y 1-y Ce y )3Al5O 12 1-z [Al2O3] z 、[(Lu 1-y Ce y )3Al5O 12 1-z [Al2O3] z 、[(Y 1-x-y Gd x Ce y )3Al5O 12 1-z [Al2O3] z 、[(Lu 1-y Ce y )3(Al 1-w Ga w )3O 12 1-z [Al2O3] z (For 0 < x < 0.2 and 0 < w < 0.3), particularly preferably 0.001 < y < 0.009 and 0.45 < z < 0.7.

[0110] ​​​​Especially in the synthesis route from pure oxides, it is possible that not all of the oxide of component R is incorporated into the garnet lattice, but remains (in a very small volume fraction) as a second oxide other than aluminum oxide in the ceramic matrix. The higher the volume fraction z of Al2O3, the higher the probability that not all R is incorporated into the garnet. Although the solubility of lanthanides in Al2O3 is indeed negligible, it is possible that traces of component R remain in the volume fraction of a second phase, such as Al2O3, and are not incorporated into the first phase, such as YAG. This must be taken into account, if necessary, when calculating the oxide to be weighed. For example, to obtain the desired fraction y in the garnet lattice in the ceramic, it is necessary to weigh out a little more CeO2 than would be calculated assuming complete incorporation.

[0111] The ceramic bodies produced in this way can be further processed to obtain components for lighting equipment, such as SSL components.

[0112] Example embodiment 1: Ceramic bodies with different porosities were obtained by mixing 292.0 g Y2O3, 715.0 g Al2O3, and 3.0 g CeO2 as described above and sintering them. Assuming that Ce is completely incorporated, the ratio of the amounts is calculated as [(Y 0.993 Ce 0.007 )3AlO 12 ] 0.46 [Al2O3] 0.54 This corresponds to the composition

[0113] FIG. 3 shows the ceramic matrix thus obtained (here, by way of example, sample 1-4, with a measured porosity of 2%).

[0114] Table 2 lists the manufactured variants and their measured thermal conductivity, together with a reference manufactured without the addition of Al2O3. The addition of Al2O3 increases the thermal conductivity by about 60%, which is also shown in Figure 3.

[0115] [Table 2]

[0116] Example embodiment 2: Ceramic bodies with different porosities were obtained by mixing 716.8 g Y2O3, 1270.4 g Al2O3, and 12.8 g CeO2 as described above and sintering them. Assuming that Ce is completely incorporated, the ratio of the amounts is calculated as [(Y 0.989 Ce 0.011 )3AlO 12 ] 0.65 [Al2O3] 0.35 This corresponds to the composition

[0117] FIG. 5 shows the ceramic matrix thus obtained (here, by way of example, sample 2.3, with a measured porosity of 7%).

[0118] Example embodiment 3: Ceramic bodies with different porosities were obtained by mixing 482.9 g of Lu2O3, 617.1 g of Al2O3, and 3.3 g of CeO2 as described above and sintering them. Assuming that Ce is completely incorporated, the ratio of the amounts is calculated as [(Lu 0.992 Ce 0.008 )3AlO 12 ] 0.5 [Al2O3] 0.5 This corresponds to the composition

[0119] 6 and 7 show the ceramic matrix thus obtained (here, by way of example, sample 3.4, with a measured porosity of 4%).

[0120] Figure 8 and Table 3 list the manufactured variants and their measured scattering coefficients (see also the "Problem Setting" section), together with a reference made without the addition of Al2O3. The addition of Al2O3 does not significantly affect the scattering coefficient in the porous ceramics.

[0121] [Table 3]

[0122] Example embodiment 4: An SEM image of the cross section (polished surface) of the light conversion element was generated. The magnification was set to 2000 times, and four images of 105 μm × 150 μm were generated. This is 0.01575 mm per image. 2 is equivalent to.

[0123] The pore area was determined by image analysis, from which the pore distribution was evaluated, by assigning each pore a diameter that corresponds to the circular pore area.

[0124] Figure 9 shows the distribution of pore diameters in nm. Supplementary data is shown in tabular form below: [Table 4]

[0125] Taking into account the median of such a distribution, depending on the process control and the particle size distribution of the starting powders used, preferred median pore diameters are 100 nm to 3000 nm, particularly preferred 300 nm to 1500 nm, even more preferred 400 nm to 1200 nm. The particle sizes of YAG, LuAG and Al2O3 are of similar order of magnitude, but show a wider distribution and sometimes slightly higher median values.

Claims

1. Lighting equipment, wherein the lighting equipment is A light source for emitting primary light, particularly a light source formed as a laser or light-emitting diode, Light conversion unit and The optical conversion unit is equipped with, A light conversion element having a front and a back surface, wherein the light conversion element is designed such that primary light is irradiated onto its front surface, and secondary light with a changed wavelength relative to the primary light is emitted from its front surface, A substrate which is optionally bonded directly or indirectly to the back surface of the light conversion element, and which is preferably formed as a heat sink, A bonding material which is arbitrarily positioned between the light conversion element and the substrate, Formed by, or comprising The light conversion element comprises a first phase containing a light conversion ceramic material and a second phase containing a further ceramic material, wherein the second phase has a higher thermal conductivity than the first phase. The aforementioned light conversion element is a lighting device that includes a plurality of pores.

2. The light conversion element has a porosity of at least 0.5%, preferably at least 1.5%, particularly preferably at least 3%, and more preferably 3% to 7%, and / or The lighting device according to claim 1, wherein the light conversion element has, in cross-section, at least 200 pores per square millimeter, preferably at least 300 pores per square millimeter, and particularly preferably at least 400 pores per square millimeter.

3. The diameter of the pores, particularly the median diameter of the pores present in the cross-section, is 100 nm to 3000 nm, preferably 300 nm to 1500 nm, and more preferably 400 nm to 1200 nm, and / or The first phase comprises a plurality of crystals, the median diameter of the crystals is advantageously 300 nm to 5000 nm, particularly preferably 500 nm to 3000 nm, and / or The lighting apparatus according to claim 1 or 2, wherein the second phase comprises a plurality of crystals, and the median diameter of the crystals is advantageously 300 nm to 5000 nm, particularly preferably 500 nm to 3000 nm.

4. The lighting equipment according to claim 1 or 2, wherein the ratio of the median diameter of the pores, particularly the pores present in the cross-section, to the median diameter of the crystals of the first phase and / or the second phase, particularly the crystals of the first phase and / or the second phase present in the cross-section, is 0.02 to 10, preferably 0.06 to 5, and particularly preferably 0.13 to 2.

4.

5. At least 1%, preferably at least 5%, of the pores, particularly those present in the cross-section, are incorporated into the first phase such that the pores border only the material of the first phase, and / or At least 1%, preferably at least 5%, of the pores, particularly those present in the cross-section, are incorporated into the second phase such that the pores border only the material of the second phase, and / or The lighting equipment according to claim 1 or 2, wherein at least 1%, preferably at least 5%, of the pores, particularly those present in the cross-section, are located between the first phase and the second phase such that the pores are in contact with both the material of the first phase and the material of the second phase.

6. The aforementioned pores were formed during the sintering process and were not introduced later, for example, by selective etching, and / or The lighting equipment according to claim 1 or 2, wherein the porosity, the number of pores per square millimeter, and / or the median diameter of the pores are designed to be uniform in the light-converting element, and / or the surface of the light-converting element is the same as the cross-section inside the light-converting element, or differs from the cross-section inside the light-converting element by at most 10%.

7. The first phase has a refractive index of 1.8 or higher, particularly 1.8 to 1.9, at 500 nm, and / or The lighting equipment according to claim 1 or 2, wherein the second phase has a refractive index of 1.8 or less, particularly 1.7 to 1.8, at 500 nm.

8. The lighting equipment according to claim 1 or 2, wherein the refractive index of the first phase of the light conversion element at 500 nm is the same as or greater than the refractive index of the second phase of the light conversion element at 500 nm, and advantageously, the difference between the refractive index of the first phase of the light conversion element at 500 nm and the refractive index of the second phase of the light conversion element at 500 nm is 0.15 or less, preferably 0.1 or less, particularly preferably 0.7 or less, and even more preferably 0.5 or less.

9. The scattering coefficient of the light conversion element at a wavelength of 600 nm is 150 cm⁻¹. －１ Larger, preferably 300 cm －１ Larger, and especially preferably 300 cm －１ ~1200cm －１ The lighting equipment according to claim 1 or 2.

10. The first phase can be described as composition (A １－ｙ R ｙ ), ３ B ５ O １２ where A includes one or more elements of the group of lanthanoids and Y, R includes one or more elements of the group of lanthanoids, B includes one or more elements of the group of Al, Ga, In, y represents the ratio of R atoms at the A site of the crystal lattice, and 0 < y < 0.02, preferably 0 < y < 0.012, particularly preferably 0.001 < y < 0.009 holds. The lighting equipment according to claim 1 or 2.

11. The lighting equipment according to claim 10, wherein A is composed of one or more elements Y, Gd, and Lu, and B is composed of one or more elements Al, Ga, and In.

12. The lighting equipment according to claim 1 or 2, wherein the second phase contains or consists of aluminum oxide.

13. The lighting equipment according to claim 1 or 2, wherein the volume fraction z of the second phase satisfies 0.05 < z < 0.95, preferably 0.3 < z < 0.7, and particularly preferably 0.45 < z < 0.

7.

14. System [(Y １－ｙ Ce ｙ ) ３ Al ５ O １２ ] １－ｚ [Al ２ O ３ ] ｚ [(Lu １－ｙ Ce ｙ ) ３ Al ５ O １２ ] １－ｚ [Al ２ O ３ ] ｚ [(Y １－ｘ－ｙ Gd ｘ Ce ｙ ) ３ Al ５ O １２ ] １－ｚ [Al ２ O ３ ] ｚ [(Lu １－ｙ Ce ｙ ) ３ (Al １－ｗ Ga ｗ ) ３ O １２ ] １－ｚ [Al ２ O ３ ] ｚ The lighting equipment according to claim 1 or 2, comprising one or more of the following, wherein 0 < x < 0.2 and 0 < w < 0.

3.

15. The lighting equipment according to claim 1 or 2, wherein the thermal conductivity of the light conversion element is greater than 10 W / mK at room temperature, preferably greater than 12 W / mK, and particularly preferably greater than 14 W / mK.

16. A light conversion unit, wherein the light conversion unit is A light conversion element having a front and a back surface, wherein the light conversion element is designed such that primary light is irradiated onto its front surface, and secondary light with a changed wavelength relative to the primary light is emitted from its front surface, A substrate which is optionally bonded directly or indirectly to the back surface of the light conversion element, and which is preferably formed as a heat sink, A bonding material which is arbitrarily positioned between the light conversion element and the substrate, Formed by, or comprising The light conversion element comprises a first phase containing a light conversion ceramic material and a second phase containing a further ceramic material, wherein the second phase has a higher thermal conductivity than the first phase. The aforementioned light conversion element is a light conversion unit that includes a plurality of pores.

Images