Untitled record

The invention relates to a diode-addressed color display with a UV diode and a phosphor for LEDs, luminaires, solid-state image intensifier, image screens and monitors u. ä.

Color displays for lights, lamps, solid-state image intensifier screens and monitors to reproduce color images in true color. Technically this resolved object in that the entire color information of a color image represented by information on the three primary colors red, green and blue. From the three primary colors can be any color by additive color mixing and White produced. This principle using both the conventional color TV seher with Braun tube and the various flat panel technologies such as plasma screen, electroluminescent screen and LCD displays. There are color displays on the market, in which the color triad red, green, blue by Diode arrays with red-, green- and blue-emitting semiconductor diode is produced. However, the problem here is the true-color image reproduction, especially the pure color reproduction of green and blue. The development of UV-emitting Semiconductor diodes, the possibilities for color image reproduction for diode expanded addressed color displays because theoretically from UV light any color of visible light can be produced. Man used phosphors absorb UV light and having a wavelength in the visible range back radiate. For this conversion of the UV light in the visible range, it is known to use inorganic pigments as phosphors. For example, it is known from Jpn. J. Appl. Phys. Vol. 35 (1996) pp. L838-L839 known, ZnS: Ag, ZnS: Cu, Al, and ZnCdS: Ag as phosphors for conversion of the UV light from UV-diode in use a fluorescent color display. These and other conventional Phosphors such as Y₂O₃ : Eu indeed have a high quantum yield, their absorption in However, the near UV range, in which emit the UV diodes is very low.

It is therefore an object of the present invention, a diode-addressed color to provide display with a UV-diode and a phosphorus available whose Phosphor has a high quantum yield and a high extinction coefficients in has near-UV wavelength range and a true-color image reproduction allowed.

According to the invention the object is achieved by a diode-addressed color display with a UV diode and a phosphor of the composition LnL₃X₂ Ln = Eu³⁺, Tb³⁺, Th³⁺, Dys³⁺, Sm³⁺, L = 4-R-4'-benzophenonecarboxylic with R = Phenyl, benzyl, CH₃, CF₃, C₂H₅, F, Cl, OCH₃, CH₃CO; 4-R-4'-benzophenonacety acetylacetonate with R = phenyl, benzyl, CH₃, CF₃, C₂H₅, F, Cl, OCH₃, CH₃CO; 4-Acetophenoncarbonsäure, 4-Trifluoracetophenoncarbonsäure, 4-Acetophenonacetyla acetylacetonate, or 4-Trifloracetophenonacetylacetonat and X = 1/2 phenanthroline, 1/2 Diphenylphenanthroline, 1/2 4-Cl-phenanthroline, bipyridine 1/2, 1/2 ethylenediamine, Triphenylphosphine, trimethylphosphine oxide, triethylphosphine, 1/2 diethyl glycol dimethyl ether (diglyme) or ethanol.

Such a color display features high intrinsic emission quantum yield and a ligand-centered absorption in the near UV and the shortwave visible range 320-450 nm with high extinction Coefficients from. The UV absorption is at its maximum at 390 to 320 nm. After photophysical considerations include these two phosphorus own sheep th actually mutually exclusive. Surprisingly, it has been found, however, that Phosphors of composition LnL₃X₂ meet both criteria. The fiction, contemporary phosphors with the "antenna molecules" L, the benzophenone or Acetophenone as structural elements, have to much higher absorp- tions as classical phosphors. A variation of the ligands L allows almost linear independent introduction of high absorptions at different wavelengths in the lanthanide compounds. Concentration quenching, a general problem in classical phosphors with a high activator, is among the inventions to the invention phosphors not observed. The phosphors according to the invention are molecular compounds and therefore are generally readily soluble in polar organic Solvents. Their properties can be therefore easily investigate in solution and the test results can be transferred to the solid state. The Solubility in organic solvents also allows new design concepts for diode-addressed color display.

In the present invention, it is preferred that the addressed diodes Color display comprising a transparent polymeric coating of the phosphor composition LnL₃X₂ contains in solid solution. The coating is transpa rent, then on the dissolved phosphor particles, the light is not scattered.

The invention based on three embodiments will be further explained.

A diode-addressed color display according to the invention comprises a UV emitting de diode as the excitation source for UV-radiation and a phosphor of the composition tion LnL₃X₂ Ln = Eu³⁺, Tb³⁺, Tm³⁺, Dys³⁺, Sm³⁺, L = 4-R-4'-benzophe noncarbonsäure with R = phenyl, benzyl, CH₃, CF₃, C₂H₅, F, Cl, OCH₃, CH₃CO; 4-R-4'-benzophenonacetylacetonat with R = phenyl, benzyl, CH₃, CF₃, C₂H₅, F, Cl, OCH₃, CH₃CO; 4-Acetophenoncarbonsäure, 4-Trifluoracetophenoncarbonsäure, 4-Acetophenonacetylacetonat or 4-Trifloracetophenonacetylacetonat and X = 1/2 Phenanthroline, 1/2 diphenylphenanthroline, 1/2 4-Cl-phenanthrol in, 1/2 bipyridine, 1/2 ethylenediamine, triphenylphosphine, trimethylphosphine oxide, Triethylphos phinoxid, 1/2 diethylene glycol dimethyl ether (diglyme) or ethanol. The euro pium- or samarium phosphors convert the UV radiation into visible Red light. The terbiumhaltige phosphorus converted into green light, which thulium containing in blue and dysprosiumhaltige in blue and yellow mixed light.

In the simplest case a color display according to the invention from the UV-diode and a transparent to this applied coating the phosphor the contains. The transparent coating can, for example, the phosphorus in a solid solution in a transparent matrix of polyacrylate, polystyrene, epoxy resin or another polymer.

As mass products LEDs are usually encapsulated in epoxy housing, wherein the molded-lens of epoxy resin to improve the outcoupling the light from the diode is used. The phosphorus in this embodiment than applied contact layer between the actual diode and the epoxy-resin will. It can also be applied as a coating on the outside of the epoxy-resin be. According to another embodiment of the phosphorus in the epoxy resin is mixed and forms a solid solution.

Large two-dimensional displays can be easily produced by a Diode array is combined with the phosphor of the invention. example as may be covered by a glass plate, the diode array, which with light material triplet is printed with one red, green and blue luminous point. Of the red glowing dot contains a phosphorus LnL₃X₂, The UV-emitting diode is particularly a UV diode of InGaN or GaN and has its emission maximum between 370 and 410 nm with a FWHM <50 nm.

The phosphors according to the invention have the composition LnL₃X₂ Ln = Eu³⁺, Tb³⁺, Tm³⁺, Dys³⁺, Sm³⁺, L = 4-R-4'-benzophenonecarboxylic with R = Phenyl, benzyl, CH₃, CF₃, C₂H₅, F, Cl, OCH₃, CH₃CO; 4-R-4'-benzophenonacetyl acetonate with R = phenyl, benzyl, CH₃, CF₃, C₂H₅, F, Cl, OCH₃, CH₃CO; 4-Acetophenoncarbonsäure, 4-Trifluoracetophenoncarbonsäure, 4-Acetophenonacetyl acetonate or 4-Trifloracetophenonacetylacetonat and X = 1/2 phenanthroline, 1/2 Diphenylphenanthrol in, 1/2 4-Cl-phenanthroline, bipyridine 1/2, 1/2 ethylenediamine, Triphenylphosphine, trimethylphosphine oxide, triethylphosphine, 1/2 diethyl englykol dimethyl ether (diglyme) or ethanol. These complex coordination Compounds of the lanthanides europium, terbium, thulium, dysprosium and Samarium Eu³⁺, Tb³⁺, Tm³⁺, Dys³⁺ and Sm³⁺ as the metal center, benzo benzophenone-4-carboxylic acid or benzophenone derivatives or 4-acetylacetonate and its derivatives as charged ligands and phenanthroline, 1/2 Diphenylphenanthro lin, 1/2 4-Cl-phenanthroline, bipyridine 1/2, 1/2 ethylenediamine, triphenylphosphine oxide, trimethylphosphine oxide, triethylphosphine, 1/2 diethylene glycol dimethyl ether (diglyme) or ethanol as neutral ligands. These coordination compounds have powerful optical intraligand transitions and assets in addition to the absorp tion of the chelating ligands also effective to act as a light antennas. The Primäran excitation by ultraviolet radiation results in a ligand-centered excited state, its energy is transferred in a subsequent step to the lanthanide ion and there leads to light emission. In these compounds remain the original largely intact absorption properties of the ligands and the interligand interactions are weak. The coordinatively unsaturated lanthanide prevents the polymerization tendency of the compounds thus mononuclearly present. There are therefore, in contrast to molecular phosphors the phosphors according to the prior art, consisting of doped activator host lattices consist.

Embodiment 1

For the preparation of Tb (C₁₄H₉O₃)₃(C₂H₅OH)₂ be 1.0 mmol TbCl₃ aq in 10 ml Ethanol to a solution of 3.0 mmol of benzophenone-4-carboxylic acid (R = H) in 70 added ml of ethanol. Subsequently, 3.0 mmol NaOCH₃ added and 2 h at 60 ° C. The white precipitate is filtered off and with methanol and dried.

On excitation with 254 nm radiation a quantum yield of 70% was measured. From the excitation spectrum can be seen that the phosphorus to 375 nm can be excited.

Embodiment 2

For the preparation of Tb (C₁₄H₉O₃)₃[(C₆H₅)₃PO]₂ be 1.0 mmol Tb (C₁₄H₉O₃)₃­ (C₂H₅OH)₂ stirred with 2.3 mmol TPPO in 1,2-dichloroethane at 50 ° C for 2 h. The previously insoluble powder is thereby slowly in solution. The resulting solution can after filtration are used directly and by adding a Polymers such as polyacrylate or polystyrene to a thin transparent Beschich of the UV-emitting diode can be used.

On excitation with 254 nm radiation a quantum yield of 45% was measured. From the excitation spectrum can be seen that the phosphorus to 380 nm can be excited.

Embodiment 3

For the preparation of Eu (C₁₄H₉O₃)₃(C₁₂H_8thN₂)₂ be 1.0 mmol EuCl₃ aq in 10 ml Ethanol to a solution of 3.0 mmol of benzophenone-4-carboxylic acid (R = H) in 70 added ml of ethanol. Subsequently, 3.0 mmol NaOCH₃ added and stirred at 60 ° C for 2 h. The white precipitate is filtered off and with methanol and dried. Then, 1 mmol of the product dissolved together with 1 mmol of 1,10-phenanthroline in 50 ml of ethanol and the Suspen sion boiled for 2 hours under reflux. The resulting complex is aspirated and with ethanol and dried.

When excited with 254 nm radiation a quantum yield of 73% was measured. From the excitation spectrum can be seen that the phosphorus to 375 nm can be excited.