MN4+-ACTIVATED LUMINESCENT MATERIAL AS CONVERSION PHOSPHOR FOR LED SOLID-STATE LIGHT SOURCES

Abstract

The present invention relates to Mn.sup.4+-activated luminescent materials, to a process for the preparation thereof, and the use thereof as phosphors or conversion phosphors in light sources. The present invention furthermore relates to an emission-converting material comprising the luminescent material according to the invention, and to a light source which comprises the luminescent material according to the invention or the omission-converting material. The present invention furthermore relates to light sources, in particular LEDs, and lighting units which contain a primary light source and the luminescent material according to the invention or the emission-converting material. The Mn.sup.4+-activated luminescent materials according to the invention are suitable, in particular, for the generation of warm-white light in LEDs.

Claims

1. Compound of the general formula (I),
M.sup.1M.sup.2.sub.1-xMn.sub.xF.sub.6-x(I) where the following applies to the symbols and indices used: M.sup.1 is selected from the group consisting of Li, Na, K, Rb, Cs and mixtures of two, three or more thereof; M.sup.2 is selected from the group consisting of As, Sb, Bi and mixtures of two or three thereof; and 0<x<1.00.

2. Compound according to claim 1, characterised in that M.sup.1 is selected from the group consisting of Li, Na, K and mixtures of two or three thereof.

3. Compound according to claim 1, characterised in that M.sup.2 is selected from the group consisting of As, Sb and mixtures of As and Sb, which may optionally comprise Bi.

4. Compound according to claim 1, characterised in that 0<x0.80, preferably 0<x0.60, more preferably 0<x0.40, particularly preferably 0.001x0.20, especially preferably 0.001x0.10 and most preferably 0.001x0.010.

5. Compound according to claim 1, characterised in that the following applies to the symbols and indices used: M.sup.1 is selected from the group consisting of Li, Na, K and mixtures of two or three thereof; M.sup.2 is selected from the group consisting of As, Sb and mixtures of As and Sb, which may optionally comprise Bi; and 0<x0.60, preferably 0<x0.40, more preferably 0.001x0.20, particularly preferably 0.001x0.10 and most preferably 0.001x0.010.

6. Compound according to claim 1, characterised in that the compound is coated on the surface with another compound.

7. Process for the preparation of a compound according to claim 1, comprising the steps: a) preparation of a suspension/solution comprising M.sup.1, M.sup.2 and Mn in an HF solution; b) stirring the suspension/solution; and c) separating off the solid obtained.

8. Process according to claim 7, in which step c) is followed by the following step: d) washing and drying of the solid obtained.

9. A method for the partial or complete conversion of UV light, violet light and/or blue light into light having a longer wavelength, comprising achieving said conversion with a compound of claim 1 as a phosphor or conversion phosphor.

10. Emission-converting material comprising a compound according to claim 1 and optionally one or more further conversion phosphors.

11. Light source comprising at least one primary light source and at least one compound according to claim 1 or an emission-converting material comprising said at least one compound and optionally one or more further conversion phosphors.

12. Light source according to claim 11, where the primary light source comprises a luminescent indium aluminium gallium nitride.

13. Light source according to claim 12, where the luminescent indium aluminium gallium nitride is a compound of the formula In.sub.iGa.sub.jAl.sub.kN, where 0i, 0j, 0k and i+j+k=1.

14. Lighting unit containing at least one light source according to claim 11.

Description

EXAMPLES

[0094] Measurement Methods

[0095] The phase formation of the samples was checked by means of X-ray diffractometry. For this purpose, the Rigaku Miniflex II X-ray diffractometer with Bragg-Brentano geometry was used. The radiation source used was an X-ray tube with Cu-K radiation (A=0.15418 nm). The tube was operated with a current strength of 15 mA and a voltage of 30 kV. The measurement was carried out in an angle range from 10 to 80 at 100.Math.min.sup.1.

[0096] The emission spectra were recorded using an Edinburgh Instruments Ltd. fluorescence spectrometer fitted with mirror optics for powder samples, at an excitation wavelength of 450 nm. The excitation source used was a 450 W Xe lamp. For temperature-dependent measurement of the emission, the spectrometer was fitted with an Oxford Instruments cryostat (MicrostatN2). The coolant employed was nitrogen.

[0097] Reflection spectra were determined using an Edinburgh Instruments Ltd. fluorescence spectrometer. For this purpose, the samples were placed and measured in a BaSO.sub.4-coated Ulbricht sphere. Reflection spectra were recorded in a range from 250 to 800 nm. The white standard used was BaSO.sub.4 (Alfa Aesar 99.998%). A 450 W Xe lamp was used as excitation source.

[0098] The excitation spectra were recorded using an Edinburgh Instruments Ltd. fluorescence spectrometer fitted with mirror optics for powder samples, at 550 nm. The excitation source used was a 450 W Xe lamp.

Example 1: Preparation of NaAs.SUB.0.995.Mn.SUB.0.005.F.SUB.5.995

[0099] 2.0 g of NaAsF.sub.6 (9.4 mmol) and 0.05 g (0.2 mmol) of K.sub.2MnF.sub.6 are suspended in 5 ml of concentrated HF and stirred for about 2 h at 70 C. The crude product is subsequently filtered off with suction and washed a number of times with cold acetone until the material is acid-free. The pale-yellow powder obtained is dried in vacuo in a desiccator for 8 h. The CIE1931 colour point is at x=0.688 and y=0.312. The lumen equivalent is 231 lm/W.sub.opt.

Example 2: Preparation of LiAs.SUB.0.995.Mn.SUB.0.005.F.SUB.5.995

[0100] 2.0 g of LiAsF.sub.6 (10.2 mmol) and 0.05 g (0.2 mmol) of K.sub.2MnF.sub.6 are suspended in 5 ml of concentrated HF and stirred for about 2 h at 70 C. The crude product is subsequently filtered off with suction and washed a number of times with cold acetone until the material is acid-free. The pale-yellow powder obtained is dried in vacuo in a desiccator for 8 h.

Example 3: Preparation of KAs.SUB.0.995.Mn.SUB.0.005.F.SUB.5.995

[0101] 2.0 g of KAsF.sub.6 (8.8 mmol) and 0.05 g (0.2 mmol) of K.sub.2MnF.sub.6 are suspended in 5 ml of concentrated HF and stirred for about 2 h at 70 C. The crude product is subsequently filtered off with suction and washed a number of times with cold acetone until the material is acid-free. The pale-yellow powder obtained is dried in vacuo in a desiccator for 8 h.

Example 4: Preparation of NaSb.SUB.0.995.Mn.SUB.0.005.F.SUB.5.995

[0102] 2.0 g of NaSbF.sub.6 (7.7 mmol) and 0.05 g (0.2 mmol) of K.sub.2MnF.sub.6 are suspended in 5 ml of concentrated HF and stirred for about 2 h at 70 C. The crude product is subsequently filtered off with suction and washed a number of times with cold acetone until the material is acid-free. The pale-yellow powder obtained is dried in vacuo in a desiccator for 8 h.

Example 5: Preparation of LiSb.SUB.0.995.Mn.SUB.0.005.F.SUB.5.995

[0103] 2.0 g of LiSbF.sub.6 (8.2 mmol) and 0.05 g (0.2 mmol) of K.sub.2MnF.sub.6 are suspended in 5 ml of concentrated HF and stirred for about 2 h at 70 C. The crude product is subsequently filtered off with suction and washed a number of times with cold acetone until the material is acid-free. The pale-yellow powder obtained is dried in vacuo in a desiccator for 8 h.

Example 6: Preparation of KSb.SUB.0.995.Mn.SUB.0.005.F.SUB.5.995

[0104] 2.0 g of KSbF.sub.6 (7.3 mmol) and 0.05 g (0.2 mmol) of K.sub.2MnF.sub.6 are suspended in 5 ml of concentrated HF and stirred for about 2 h at 70 C. The crude product is subsequently filtered off with suction and washed a number of times with cold acetone until the material is acid-free. The pale-yellow powder obtained is dried in vacuo in a desiccator for 8 h.

Example 7: Production and Measurement of LEDs Using the Luminescent Materials

[0105] General procedure for the production and measurement of pc-LEDs: A mass m.sub.phos (in g) of the luminescent material indicated in the respective LED example and a mass m.sub.YAG:Ce (in g) (obtainable under the trade name U728 from Philips) are weighed out, m.sub.silicone (in g) of an optically transparent silicone is added, and the components are subsequently mixed homogeneously in a planetary centrifugal mixer, so that the concentration of the luminescent material in the total mass is c.sub.phos (in % by weight). The silicone/luminescent material mixture obtained in this way is applied to the chip of a blue semiconductor LED with the aid of an automatic dispenser and cured with supply of heat. The reference LED indicated in the present examples for the LED characterisation was filled with pure silicone without luminescent material. The blue semiconductor LEDs used have an emission wavelength of 450 nm and are operated with a current strength of 350 mA. The photometric characterisation of the LEDs is carried out using an Instrument Systems CAS 140 spectrometer and an ISP 250 integration sphere connected thereto. The LED is characterised by determination of the wavelength-dependent spectral power density. The resultant spectrum of the light emitted by the LED is used to calculate the colour point coordinates CIE x and y.

[0106] The sample weights of the luminescent materials and other materials used in the respective example and the colour coordinates of the LEDs obtained in accordance with the general procedure described above are summarised in Table 1. The associated LED spectra are depicted in FIG. 5.

TABLE-US-00001 TABLE 1 Composition and properties of LED A and LED B produced. LED A (2700 K) LED B (3000 K) with phosphor with phosphor Parameter from Example 1: from Example 1: M.sub.phos/g 8.43 6.84 m.sub.YAG:Ce/g 0.71 0.71 M.sub.silicone 4.46 4.41 C.sub.phos /% by wt. 62.0 57.2 c.sub.YAG:Ce/% by wt. 5.22 5.94 CIE 1931 x 0.403 0.4338 CIE 1931 y 0.410 0.4578

DESCRIPTION OF THE FIGURES

[0107] FIG. 1: X-ray powder diffraction pattern (Cu-K.sub. radiation) of NaAs.sub.0.995Mn.sub.0.005F.sub.5.995 (Example 1).

[0108] FIG. 2: Reflection spectrum of NaAs.sub.0.995Mn.sub.0.005F.sub.5.995 (Example 1).

[0109] FIG. 3: Excitation spectrum of NaAs.sub.0.995Mn.sub.0.005F.sub.5.995 (Example 1) (.sub.em=627 nm).

[0110] FIG. 4: Emission spectrum of NaAs.sub.0.995Mn.sub.0.005F.sub.5.995 (Example 1) (.sub.ex=465 nm).

[0111] FIG. 5: Spectra of LED A and LED B comprising YAG:Ce and NaAsF.sub.6:Mn.sup.4+ (Example 1) for the colour temperatures 2700 and 3000 K.