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• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
  • B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
  • C09K11/025—Use of particular materials as binders, particle coatings or suspension media therefor non-luminescent particle coatings or suspension media
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/67—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing refractory metals
  • C09K11/68—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing refractory metals containing chromium, molybdenum or tungsten
  • C09K11/685—Aluminates; Silicates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals

Definitions

• the invention relates to coated phosphor particles with improved refractive index and a process for their preparation.
• LED conversion phosphors such as YAGrCe, TAG: Ce, Al 2 O 3 : Ce etc. have a high refractive index of about 1, 8 and above.
• the phosphors are usually embedded in a binder (usually silicone or epoxy resin); this mixture represents the
• the binders have a refractive index within a range of 1, 4 to 1, 5 on.
• the 0.4-index jump in refractive index between binder and phosphor results in a significant portion of the light in the conversion layer being scattered at the binder / phosphor interface. This relates in particular both to the light coupling, d. H. the light of the LED chip, which is to excite the phosphor, as well as on the outcoupling, d. H. the fluorescent light which is produced within the phosphor and is to be emitted by it. Overall, the large and abrupt refractive index jump causes one
• the resulting effective refractive index of the binder is then given by the sum of the volumetrically averaged refractive indices of the binder and the high refractive ultrafine particles, only an insufficiently small increase in the refractive index is possible. This is all the more true, as well as the concentration of the added Feinstpitate can not be increased arbitrarily, because otherwise there is a detrimental change in the processing properties of the binder mixture.
• Another way to increase the refractive index of the binder is to use special functional groups z. B. in the silicone structure, in particular aromatics.
• this proves to be disadvantageous because the so modified silicones have a lower radiation and temperature resistance than unmodified silicones.
• so modified binders can not be used, because it can come after a few hundred hours of operation to a degradation of the binder, which can be noticeable in the form of a graying. This contradicts the long life of the LED chip of up to 100,000 operating hours.
• a glass coating of a ceramic containing phosphor particles is known, wherein the phosphor particles have a particle size between 50 and 250 nm, preferably 150 microns.
• the phosphor particles are produced by means of conventional solid-state synthesis ("mixing and firing").
• a coating of ZnS-based phosphor particles is known, wherein the coating consists of trimethyl or triethylaluminum and is brought via a CVD method (chemical vapor deposition) on the phosphor particles.
• CVD processes are very complicated in terms of process engineering and apparatus: very high purities of the (inert) gas atmosphere are required over the entire process and the fluidic design must be such that a homogeneous supply of the individual gas streams to the material to be coated can take place.
• the object of the present invention was to achieve an improvement of Lichtein- and -auskopplung in and out of the phosphor without other properties, such. B. deteriorate the life of the LED system.
• the object is achieved by converting a phosphor in a wet-chemical process with an inorganic coating into a new phosphor material, which improves the coupling and decoupling of light.
• this is a porous coating with a medium or high material
• the present invention thus provides coated phosphor particles containing luminescent particles and at least one metal, transition metal or Halbmetalloxidbe Anlagenung obtainable by mixing at least two educts with at least one dopant and subsequent, preferably multi-stage, calcination to phosphor particles and coating with metal, transition metal or Semi-metal oxides by wet-chemical methods and recalcined calcination.
• the metal, transition metal or semi-metal coating is preferably substantially transparent, ie it must ensure a 90% to 100% transparency both for the excitation spectrum as well as for the emission spectrum of the conversion phosphors used in each case. On the other hand, the transparency of the invention
• Coating for all wavelengths that do not meet the excitation and emission wavelengths also less than 90% to 100% amount.
• the resulting phosphor material according to the invention has, due to the outwardly increasing porosity in the coating, an effective refractive index which decreases with increasing distance from the surface of the original phosphor (see FIGS. 1 and 2).
• the refractive index decreases steadily from the value of the bulk refractive index of the original phosphor to the refractive index of the binder (e.g.
• Epoxy or silicone resin in which the new phosphor material is suspended. In this case, no refractive index jumps occur, so that the light scattering is reduced during the transition through the binder-new phosphor material interface. Incoming and outgoing light then no longer sees a sharp phase boundary at which reflection can take place
• the coated phosphor surface according to the invention is preferably mesoporous or macroporous, with “mesoporous” a pore opening between 2 to 50 nm and “macroporous” a pore size> 50 nm describes.
• the particle size of the phosphors according to the invention is between 50 nm and 40 .mu.m, preferably between 1 .mu.m and 20 .mu.m.
• the thickness of the coating according to the invention is between 10 nm and 200 nm, preferably 15 nm and 100 nm
• Primary particles of the metal, transition metal or Halbmetalloxid- coating is between 5 nm and 50 nm.
• Molybdates tungstates, vanadates, Group III nitrides, oxides, either individually or mixtures thereof with one or more activator ions such as Ce, Eu, Mn, Cr, Tb and / or Bi.
• the metal in another preferred embodiment, is the metal,
• Transition metal or Halbmetalloxid coating of at least two components A and B of different refractive index is constructed so that a refractive index gradient results from the inside to the outside, with the higher refractive index inside and the lower refractive index outside. Such a coating exists on the surface of the
• a mixture of A and B is present with a gradient of composition.
• a and B are:
• Al 2 O 3 and SiO 2 , ZnO and SiO 2 or ZrO 2 and SiO 2 examples of mixtures of more than two components are ZnO 2 , AbO 3 and SiO 2 or TiO 2 ; AbO 3 and SiO 2 .
• Preferred components for A and B are Al 2 O 3 and SiO 2 .
• the coating may be dense or porous, the latter being preferred. It can be as mixed precipitation of the components or alternating cases of the
• the reflection-reducing coating consists only of a material of average refractive index, whose optical thickness is one quarter of the wavelength of the incident or emitted light or an odd multiple thereof.
• Such a layer consists for example of aluminum silicate or a mixture of aluminum oxide and SiO 2 .
• the reflection-reducing coating consists of a multilayer arrangement of alternating layers of high and low refractive index.
• the optical thickness of the layers is tuned so that the reflection at the wavelength of the incident light to excite the luminescence and / or the wavelength of the luminescence is minimal. This is in e.g. then the case when the optical thickness of the layers corresponds to a quarter of the wavelength of the light. The optimal geometric thickness of the layers then results after the
• Formula d k * ( ⁇ / 4 n g ), where d is the layer thickness, ⁇ is the wavelength of the light and n g is the refractive index of the layer and k is an integer odd number, preferably 1.
• the layer thicknesses are optimized so that both the reflection at the excitation and the emission wavelength is greatly reduced. In order to optimize the overall result, it is possible to deviate from the optimum layer thicknesses for the specific wavelengths of the excitation and emission.
• High-index layers in this embodiment preferably consist of titanium dioxide, Sn 2 O or Z 1 O 2 , low refractive index layers of SiO 2 or MgF 2 .
• the coating of the phosphor particles is preferably carried out wet-chemically by precipitating the metal oxides or hydroxides in aqueous suspension.
• the uncoated phosphor is suspended in water in a reactor and coated by simultaneous addition of a metal salt and a precipitating agent with stirring with the metal oxide or hydroxide.
• organometallic compounds e.g. Metal alcoholates are added, which then form metal oxides or hydroxides by hydrolytic decomposition.
• Another possible way of coating the particles is coating over a SoI gel.
• This method is particularly suitable for water-sensitive materials as well as for acid or alkali-sensitive substances.
• a further subject of the present invention is therefore a process for the preparation of coated phosphor particles with at least one substantially transparent metal, transition metal or semimetal oxide, characterized by the steps:
• T ⁇ iscrc. b. the pre-calcined phosphor precursor mixture is then calcined at a temperature T 2> 800 0 C to phosphor particles.
• the educts for producing the phosphor consist of the base material (for example salt solutions of aluminum, yttrium and cerium) and at least one dopant, preferably europium or cerium and optionally further Gd, Lu, Sc, Sm , Tb, Pr and / or Ga- containing materials.
• the base material for example salt solutions of aluminum, yttrium and cerium
• the dopant preferably europium or cerium and optionally further Gd, Lu, Sc, Sm , Tb, Pr and / or Ga- containing materials.
• Suitable starting materials are inorganic and / or organic substances such as nitrates, carbonates, bicarbonates, phosphates, carboxylates, alcoholates, acetates, oxalates, halides, sulfates, organometallic compounds, hydroxides and / or oxides of metals, semimetals, transition metals and / or rare earths , which are dissolved and / or suspended in inorganic and / or organic liquids.
• Preferably mixed nitrate solutions, chloride or hydroxide solutions are used which contain the corresponding elements in the required stoichiometric ratio.
• substantially transparent oxides for the coating preference is given to using aluminum oxide, zinc oxide, titanium dioxide, zirconium oxide or silicon oxide or combinations thereof. Particular preference is given to using aluminum oxide.
• the wet-chemical preparation generally has the advantage over the conventional solid-state diffusion method (English, mixing and firing) that the resulting materials have a higher uniformity with respect to the stoichiometric composition, the particle size and the morphology of the particles from which the phosphor according to the invention is produced.
• aqueous precursor of the phosphors consisting e.g. from a mixture of yttrium nitrate, aluminum nitrate and cerium nitrate solution
• phosphor precursors consisting e.g. from a mixture of yttrium nitrate, aluminum nitrate and cerium nitrate solution
• spray pyrolysis also called spray pyrolysis
• aqueous or organic salt solutions educts
• Precipitating agent consisting of citric acid and ethylene glycol added and then heated. Increasing the viscosity causes phosphor precursor formation.
• the abovementioned nitrate solutions of the corresponding phosphorus starting materials are dissolved in water, then boiled under reflux and admixed with urea, whereby the phosphor precursor slowly forms.
• Spray pyrolysis belongs to the aerosol processes which are characterized by spraying solutions, suspensions or dispersions into a reaction chamber (reactor) which has been heated in different ways, as well as the formation and separation of solid particles.
• a reaction chamber reactor
• hot gas temperatures ⁇ 200 0 C find in the spray pyrolysis as a high-temperature process except the
• the production of the phosphors according to the invention can be carried out by various wet-chemical methods, by 1) a homogeneous precipitation of the constituents, followed by the
• Spray process and removal of the solvent is carried out, followed by a one- or multi-stage thermal aftertreatment, one step of which can be carried out in a reducing atmosphere, or
• the mixture is finely divided, for example by means of a Spray process and removal of the solvent is accompanied by pyrolysis, followed by a one- or multi-stage thermal aftertreatment, one step of which can be carried out in a reducing atmosphere.
• the wet-chemical preparation of the phosphor preferably takes place by the precipitation and / or sol-gel process.
• the annealing be carried out at least partially under reducing conditions (e.g., with carbon monoxide, forming gas, pure hydrogen, mixtures of hydrogen with an inert gas or at least vacuum or
• Oxygen deficiency atmosphere is performed.
• any of the outer forms of the phosphor particles such as spherical particles, platelets, and structured materials and ceramics, can be made by the above methods.
• the excitability of the phosphors according to the invention also extends over a wide range, ranging from about 250 nm to 560 nm, preferably 380 nm up to about 500 nm.
• these phosphors are suitable for excitation by UV or blue-emitting primary light sources such as LEDs or conventional discharge lamps (eg based on Hg).
• Another object of the present invention is a lighting unit with at least one primary light source whose emission maximum or maximum ranges in the range 380 nm to 530 nm, preferably 430 nm to about 500 nm.
• Particularly preferred is a range between 440 and 480 nm, wherein the primary radiation is partially or completely converted by the coated phosphors according to the invention into longer-wave radiation.
• this lighting unit emits white or emits light with a certain color point (color-on-demand principle).
• the person skilled in possible forms of such light sources are known. These may be light-emitting LED chips of different construction.
• the light source is a luminescent arrangement based on ZnO, TCO (transparent conducting oxide), ZnSe or SiC or else an arrangement based on an organic light-emitting layer (OLED).
• the light source is a source that shows electroluminescence and / or photoluminescence. Furthermore, the light source may also be a plasma or discharge source.
• the phosphors of the present invention may be either dispersed in a resin (eg, epoxy or silicone resin), placed directly on the primary light source, or remotely located therefrom, depending on the application (the latter arrangement also incorporates "remote phosphor technology”).
• a resin eg, epoxy or silicone resin
• the advantages of "remote phosphor technology” are known to the person skilled in the art and can be found, for example, in the following publication: Japanese Journ. of Appl. Phys. VoI 44, no. 21 (2005). L649-L651.
• Coupling of the illumination unit between the coated phosphor and the primary light source is realized by a light-conducting arrangement.
• the primary light source is installed at a central location and this is optically coupled to the phosphor by means of light-conducting devices, such as light-conducting fibers.
• the lighting requirements adapted lights can only be realized consisting of one or different phosphors, which can be arranged to form a luminescent screen, and a light guide, which is coupled to the primary light source realize.
• Another object of the present invention is the use of the phosphors according to the invention for the partial or complete conversion of blue or in the near UV emission of a light-emitting diode. Further preferred is the use of the phosphors according to the invention for the conversion of blue or near-UV emission into visible white radiation. Furthermore, the use of the phosphors according to the invention for converting the primary radiation into a specific color point according to the "color on demand" concept is preferred.
• Another object of the present invention is the use of the phosphors according to the invention in electroluminescent materials, such as electroluminescent films (also light-emitting or
• Called light foils in which, for example, zinc sulfide or zinc sulfide doped with Mn 2+ , Cu + , or Ag + is used as the emitter, which emit in the yellow-green range.
• the fields of application of the electroluminescent film are, for example, advertising, backlighting in liquid crystal displays (LC displays) and
• Thin-film transistor displays TFT displays
• self-illuminating license plates floor graphics (in combination with a non-slip and non-slip laminate), in display and / or control elements, for example in automobiles, trains, ships and aircraft or even household, gardening , Measuring or sports and leisure equipment.
• the two aqueous solutions (a) and (b) are added simultaneously to 200 ml of deionized water while stirring within 15 min. It is stirred for another 15 min.
• the resulting solution is evaporated to dryness and treated in air atmosphere at a temperature of 800 0 C for one hour, so that the Rubinplättchen result.
• Phosphor is finally annealed for 30 min at 750 0 C and finally sieved through a 50 ⁇ sieve.
• the product disintegrates into a fine powder, which falls through the sieve practically without residue in a short time.
• Example 2 Coating of ruby platelets with alumina and silica
• the pH is kept constant at 6.5 by addition of sodium hydroxide solution. After the end of the metered addition is stirred for 1 hour at 8O 0 C, then the pH is adjusted to 7.5 and 80 g of sodium silicate (adjusted to 12.5 wt.% SiO 2 ) are added at 0.75 ml / min , The pH is kept constant with hydrochloric acid. After the addition of water glass is stirred for one hour at the precipitation temperature and cooled to room temperature. The product obtained is filtered off, washed with water and dried. The dried phosphor is finally calcined for 30 minutes at 750 0 C and finally sieved through a 50 ⁇ sieve.
• TEOS tetraethyl orthosilicate
• Example 5 Coating of the phosphor (Ca, Sr, Ba) SiN 2 : Eu with aluminum oxide
• Heating mantle and reflux condenser suspended in 1 liter of ethanol To this is added a solution of 17 g of ammonia water (25% by weight of NH 3 ) in 170 g of water. While stirring, a solution of 48 g of tetraethyl orthosilicate (TEOS) in 48 g of anhydrous ethanol is slowly added dropwise (about 1 ml / min) at 65 ° C. After completion of the addition, the suspension is stirred after 2 hours, brought to room temperature and filtered off. The residue is washed with ethanol, dried, then calcined and sieved.
• TEOS tetraethyl orthosilicate
• TEOS tetraethyl orthosilicate
• Example 10 Coating of the Phosphor YAG: Ce with a Mixture of Al 2 O 3 and SiO 2 In a glass reactor with a heating jacket, 75 g of a filter cake, the
• FIG. 1 the phosphor particle (1) is provided with a coating (3), which becomes more porous toward the outside, in a wet-chemical process (2).
• the entirety of (1) + (3) represents the new phosphor material.
• the new phosphor material is outlined: the new phosphor material is formed from the phosphor (1) by a porous coating (3) is firmly attached to the surface via chemical links. The coating causes a gradual transition between the refractive index of the high refractive index phosphor (n-i) and the refractive index of the low refractive index resin (n_ ⁇ ) takes place. This will be less
• the phosphor can absorb more light and decouple more fluorescent light.
• Fiq. 4 shows an SEM image of a phosphor Al 2 O 3 : Cr 3+ coated with a mixed precipitate of Al 2 O 3 and SiO 2 with a refractive index gradient of pure aluminum oxide (about 1.78) on SiO 2 (about 1, 4).

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• 2007
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