GREEN EMITTING PHOSPHOR AND LIGHTING DEVICE

Abstract

The disclosure provides a potassium aluminate phosphor which is doped with Mn+ or with Eu+ and Mn+, a lighting device, and methods for making the same. This disclosure also provides a conversion light emitting diode (LED) including a semiconductor layer sequence set up to emit electromagnetic primary radiation; and a conversion element including an Mn.sup.2+-doped potassium aluminate phosphor or an Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor and at least partly converts the electromagnetic primary radiation to electromagnetic secondary radiation, wherein the Mn.sup.2+-doped potassium aluminate phosphor or the Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor has a general empirical formula K.sub.xAl.sub.11+yO.sub.17+z:Mn.sup.2+, or K.sub.xAl.sub.11+yO.sub.17+z:(Mn.sup.2+,Eu.sup.2+).

Claims

1.-14. (canceled)

15. A conversion light emitting diode (LED) comprising: a semiconductor layer sequence configured to emit electromagnetic primary radiation; and a conversion element comprising an Mn.sup.2+-doped potassium aluminate phosphor or an Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor, wherein the conversion element at least partly converts the electromagnetic primary radiation to electromagnetic secondary radiation, wherein the Mn.sup.2+-doped potassium aluminate phosphor or the Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor has a general empirical formula
K.sub.xAl.sub.11+yO.sub.17+z:Mn.sup.2+, or
K.sub.xAl.sub.11+yO.sub.17+z:(Mn.sup.2+,Eu.sup.2+), where x+3(11+y)=2(17+z), 0<x<2, −½<z<½, and −⅓<y<⅓.

16. The conversion LED of claim 15, wherein the Mn.sup.2+-doped potassium aluminate phosphor or the Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor has the general empirical formula K.sub.xAl.sub.11+yO.sub.17+z:Mn.sup.2+ or K.sub.xAl.sub.11+yO.sub.17+z:(Mn.sup.2+,Eu.sup.2+) with 0<x<2, where when 0<x<1, then y=⅓ (1−x) and z=0 or y=0 and z=−½ (1−x); when x=1, then y=0 and z=0; and when 1<x<2, then y=0 and z=½ (x−1) or y=−⅓ (x−1) and z=0.

17. The conversion LED of claim 15, wherein the Mn.sup.2+-doped potassium aluminate phosphor or the Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor has the general empirical formula K.sub.xAl.sub.11+yO.sub.17+z:Mn.sup.2+ or K.sub.xAl.sub.11+yO.sub.17+z:(Mn.sup.2+,Eu.sup.2+) with 0.5<x<1.5, wherein when 0.5<x<1, then y=⅓ (1−x) and z=0 or y=0 and z=−½ (1−x); when x=1, then y=0 and z=0; and when 1<x<1.5, then y=0 and z=½ (x−1) or y=−⅓ (x−1) and z=0.

18. The conversion LED of claim 15, wherein the Mn.sup.2+-doped potassium aluminate phosphor or the Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor has the general empirical formula K.sub.xAl.sub.11+yO.sub.17+z:Mn.sup.2+ or K.sub.xAl.sub.11+yO.sub.17+z:(Mn.sup.2+,Eu.sup.2+) with 0.7≤x≤1.3, wherein when 0.7≤x<1, then y=⅓ (1−x) and z=0 or y=0 and z=−½ (1−x); when x=1, then y=0 and z=0; and when 1<x≤1.3, then y=0 and z=½ (x−1) or y=−⅓ (x−1) and z=0.

19. The conversion LED of claim 18, wherein 0.8≤x≤1.2 and when 0.8≤x<1, then y=⅓ (1−x) and z=0; when x=1, then y=0 and z=0; and when 1<x≤1.2, then y=0 and z=½ (x−1).

20. The conversion LED of claim 18, wherein 0.8≤x≤1.2 and when 0.8≤x<1, then y=0 and z=−½ (1−x); when x=1, then y=0 and z=0 and when 1<x≤1.2, then y=−⅓ (x−1).

21. The conversion LED of claim 15, wherein the Mn.sup.2+-doped potassium aluminate phosphor or the Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor crystallizes in the hexagonal P6.sub.3/mmc space group.

22. The conversion LED of claim 15, wherein the Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor has the general empirical formula K.sub.xAl.sub.11+yO.sub.17+z:(Mn.sup.2+,Eu.sup.2+).

23. The conversion LED of claim 15, wherein the Mn.sup.2+-doped potassium aluminate phosphor is a product of reactants K.sub.2CO.sub.3, Al.sub.2O.sub.3, and MnCO.sub.3.

24. The conversion LED of claim 15, wherein the Eu.sup.2+- and Mn.sup.2+-doped potassium aluminate phosphor is a product of reactants K.sub.2CO.sub.3, Al.sub.2O.sub.3, MnCO.sub.3, and Eu.sub.2O.sub.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0088] In the following, the phosphor and the lighting device described herein are explained in more detail in conjunction with non-limiting aspects and the associated figures.

[0089] FIG. 1 shows a detail of the crystal structure of the phosphor of the disclosure.

[0090] FIGS. 2, 3, 4A, 5 show emission spectra.

[0091] FIG. 4B shows a comparison of optical data of phosphors.

[0092] FIGS. 6, 7 and 8 show conversion LEDs.

[0093] The figures and the proportions of the elements depicted in the figures relative to each other are not to be considered as true to scale. Rather, individual elements may be displayed in an exaggeratedly large format for better presentation and/or comprehensibility.

DETAILED DESCRIPTION

[0094] FIG. 1 shows a detail of the crystal structure of the phosphor K.sub.xAl.sub.11+yO.sub.17+z:(Mn.sup.2+, Eu.sup.2+) or K.sub.xAl.sub.11+yO.sub.17+z:Mn.sup.2+ along the crystallographic b axis. The hatched triangles are AlO.sub.4 tetrahedra and AlO.sub.6 octahedra in which Al is at the centers and oxygen is at the vertices of the tetrahedra or octahedra. The AlO.sub.4 tetrahedra and AlO.sub.6 octahedra form spinel-like layers. Between the layers are arranged K.sup.+ ions with the Wyckoff position 2d or the Wyckoff position 2d and 12j (table 3) and O.sup.2− ions (not shown). Mn.sup.2+ or Mn.sup.2+ and Eu.sup.2+ here may partly replace K.sup.+ or Al.sup.3+.

[0095] If the proportion x of potassium is 0<x<1, the Wyckoff position 2d is not fully occupied by potassium ions and the Wyckoff position 12j is unoccupied.

[0096] If the proportion x of potassium is x=1, the Wyckoff position 2d is fully occupied by potassium ions and the Wyckoff position 12j is unoccupied.

[0097] If the proportion x of potassium is 1<x<2, the Wyckoff position 2d is fully occupied by potassium ions and the Wyckoff position 12j is partly occupied by potassium ions.

[0098] FIG. 2 shows the emission spectrum of KAl.sub.11O.sub.17:Mn.sup.2+ (AB1). Plotted on the x axis is the wavelength in nm, and on the y axis the intensity in percent. To measure the emission spectrum, the phosphor was excited with primary radiation having a peak wavelength of 460 nm. The phosphor has a peak wavelength of about 509 nm and a full width at half maximum of 24 nm.

[0099] FIG. 3 shows the emission spectrum of K.sub.xAl.sub.11+yO.sub.17+z:(Mn.sup.2+,Eu.sup.2+) with x=1.2; z=0 and y=−⅓ (x−1) (AB2). Plotted on the x axis is the wavelength in nm, and on the y axis the intensity in percent. To measure the emission spectrum, the phosphor was excited with primary radiation having a peak wavelength of 460 nm. The phosphor has a peak wavelength of about 511 nm and a full width at half maximum of 23 nm.

[0100] Table 5 below shows a comparison of emission properties of AB1, AB2 and VB1.

TABLE-US-00005 TABLE 5 λ.sub.prim λ.sub.peak FWHM LER (nm) (nm) (nm) (lmW.sup.−1) VB1 400 450 51 0.137 VB1 460  *— — — AB1 400 **— — — AB1 460 509 24 0.533 AB2 400 511 23 0.509 AB2 460 511 23 0.542 *Not measurable owing to overlap with primary radiation (λ.sub.prim). **Excitation not possible with primary radiation (λ.sub.prim) of 400 nm.

[0101] As apparent from table 5, the peak wavelengths of working examples AB1 and AB2 are in the green region of the electromagnetic spectrum with full widths at half maximum below 30 nm, while the peak wavelength of the solely Eu.sup.2+-doped potassium aluminate phosphor (VB1) is in the blue region of the electromagnetic spectrum with a full width at half maximum of 51 nm. In some aspects, doping of the potassium aluminate with Mn.sup.2+ or co-doping of the already Eu.sup.2+-doped potassium aluminate with Mn.sup.2+ results in a shift in the peak wavelength into the green region of the electromagnetic spectrum and a distinct reduction in the half height width of the emission band. It is thus possible with AB1 and AB2 to achieve a distinctly higher light yield (LER) than with VB1.

[0102] The phosphor of the disclosure may be present as the sole phosphor in a lighting device or conversion LED which, in full conversion, emits overall radiation in the green region of the electromagnetic spectrum or, in partial conversion, emits overall radiation in the blue to green region of the electromagnetic spectrum. The lighting device or conversion LED that emits overall radiation in the blue to green region of the electromagnetic spectrum, in partial conversion, is suitable, for example, for signal lights such as blue lights, for example, police vehicles, ambulances, emergency doctors' vehicles or fire department vehicles.

[0103] FIG. 4A shows emission spectra of the phosphor AB2 and two comparative examples Ca.sub.8Mg(SiO.sub.4).sub.4Cl.sub.2: Eu.sup.2+ (VB2) and Ca.sub.3Sc.sub.2Si.sub.3O.sub.12:Ce.sup.3+ (VB3).

[0104] FIG. 4B shows a comparison of optical data of the phosphor AB2 and two comparative examples Ca.sub.8Mg(SiO.sub.4).sub.4Cl.sub.2:Eu.sup.2+ (VB2) and Ca.sub.3Sc.sub.2Si.sub.3O.sub.12:Ce.sup.3+ (VB3). The phosphors show a similar peak wavelength. AB2, compared to VB2 and VB3, shows a distinctly smaller full width at half maximum. By virtue of the small full width at half maximum, the phosphor of the disclosure has distinctly smaller radiation losses caused by partial emission in the UV region than conventional phosphors with peak wavelengths in the green region of the electromagnetic spectrum.

[0105] FIG. 5 shows emission spectrum of the phosphor AB2 and of a comparative example Ca.sub.8Mg(SiO.sub.4).sub.4Cl.sub.2:Eu.sup.2+ (VB2). In addition, FIG. 5 shows the melanopic sensitivity curve M. The melanopic sensitivity curve M shows the wavelengths with which melatonin production in the body can be best suppressed. As apparent, the emission spectrum of AB2 has a much greater overlap with the melanopic sensitivity curve M than the emission spectrum of VB2. It is consequently possible with the phosphor of the disclosure to generate melanopically effective light, such that this light can be used effectively for suppression of melatonin formation. If a person is exposed to the radiation from a lighting device containing the phosphor AB2, this can lead to increased attentiveness or else the ability of the person to concentrate. Lighting devices including the phosphor of the disclosure can thus be used for room lighting, for example, for “human centric lighting” applications.

[0106] FIGS. 6 to 8 each show schematic side views of various aspects of lighting devices described here, for example, conversion LEDs.

[0107] The conversion LEDs of FIGS. 6 to 8 include at least one Mn.sup.2+ or Eu.sup.2+ and Mn.sup.2+-doped potassium aluminate phosphor described here. In addition, a further phosphor or a combination of phosphors may be present in the conversion LED. The additional phosphors are known to the person skilled in the art and are therefore not mentioned explicitly at this point.

[0108] The conversion LED according to FIG. 6 has a semiconductor layer sequence 2 disposed on a substrate 10. The substrate 10 may, for example, be in reflective form. Disposed atop the semiconductor layer sequence 2 is a conversion element 3 in the form of a layer. The semiconductor layer sequence 2 has an active layer (not shown) that emits with a wavelength between 330 nm and 470 nm inclusive in the operation of the conversion LED. The conversion element 3 is disposed in the beam path of the primary radiation S. The conversion 3 includes a matrix material, for example a silicone, epoxy resin or hybrid material, and particles of the phosphor 4.

[0109] For example, the phosphor 4 has an average grain size of 10 μm. The phosphor 4 is capable of converting the primary radiation S, in the operation of the conversion LED, at least partly or fully to a secondary radiation SA in the green spectral region. The phosphor 4 is distributed homogeneously in the matrix material in the conversion element 3 within the scope of manufacturing tolerance.

[0110] Alternatively, the phosphor 4 may also be distributed in the matrix material with a concentration gradient.

[0111] Alternatively, the matrix material may also be absent, such that the phosphor 4 takes the form of a ceramic converter.

[0112] The conversion element 3 is applied over the full area of the radiation exit surface 2a of the semiconductor layer sequence 2 and over the lateral surfaces of the semiconductor layer sequence 2, and is in direct mechanical contact with the radiation exit surface 2a of the semiconductor layer sequence 2 and the lateral surfaces of the semiconductor layer sequence 2. The primary radiation S can also exit via the lateral surfaces of the semiconductor layer sequence 2.

[0113] The conversion element 3 may be applied, for example, by injection molding, compression-injection molding or spray-coating methods. Moreover, the conversion LED has electrical contacts (not shown here), the formation and arrangement of which is known to the person skilled in the art.

[0114] Alternatively, the conversion element may also be prefabricated and be applied to the semiconductor layer sequence 2 by means of what is called a pick-and-place process.

[0115] FIG. 7 shows a further working example of a conversion LED 1. The conversion LED 1 has a semiconductor layer sequence 2 on a substrate 10. The conversion element 3 is formed on the semiconductor layer sequence 2. The conversion element 3 takes the form of a platelet. The platelet may include particles of the phosphor 4 that have been sintered together and hence be a ceramic platelet, or the platelet includes, for example, glass, silicone, an epoxy resin, a polysilazane, a polymethacrylate or a polycarbonate as matrix material with particles of the phosphor 4 embedded therein.

[0116] The conversion element 3 has been applied over the full area of the radiation exit surface 2a of the semiconductor layer sequence 2. For example, no primary radiation S exits via the lateral surfaces of the semiconductor layer sequence 2; instead, it does so predominantly via the radiation exit surface 2a. The conversion element 3 may have been applied by means of a bonding layer (not shown), for example of silicone, atop the semiconductor layer sequence 2.

[0117] The conversion LED 1 according to FIG. 8 has a housing 11 with a recess. Disposed in the recess is a semiconductor layer sequence 2 having an active layer (not shown). In the operation of the conversion LED, the active layer emits primary radiation S with a wavelength of between 330 nm and 470 nm inclusive.

[0118] The conversion element 3 takes the form of an encapsulation of the layer sequence in the recess, and includes a matrix material, for example a silicone, and a phosphor 4, for example KAl.sub.11O.sub.17:(Mn.sup.2+,Eu.sup.2+). In the operation of the conversion LED 1, the phosphor 4 converts the primary radiation S at least partly to a secondary radiation SA. Alternatively, the phosphor converts the primary radiation S fully to secondary radiation SA.

[0119] It is also possible that the phosphor 4 is arranged spaced apart from the semiconductor layer sequence 2 or the radiation exit surface 2a in the working examples of FIGS. 6 to 8. This can be achieved, for example, by sedimentation or by application of the conversion layer atop the housing.

[0120] For example, by contrast with the aspect of FIG. 8, the encapsulation may include a matrix material, for example silicone, with the conversion element 3 applied as a layer atop the housing 11 and atop the encapsulation, spaced apart on the encapsulation from the semiconductor layer sequence 2.

[0121] The working examples described in conjunction with the figures and features thereof may also be combined with one another in further working examples, even if such combinations are not shown explicitly in the figures. In addition, the working examples described in conjunction with the figures may have additional or alternative features according to the description in the general part.

LIST OF REFERENCE NUMERALS

[0122] 1 lighting device or conversion LED [0123] 2 semiconductor layer sequence or semiconductor chip [0124] 2a radiation exit surface
3 conversion element [0125] 4 phosphor [0126] 10 substrate [0127] 11 housing [0128] S primary radiation [0129] SA secondary radiation [0130] LED light-emitting diode [0131] LER light yield [0132] λ.sub.peak peak wavelength [0133] ppm parts per million [0134] AB working example [0135] VB comparative example [0136] g grams [0137] I intensity [0138] mol % mole percent [0139] nm nanometers [0140] ° C. degrees Celsius [0141] lm lumens [0142] W watts [0143] mmol millimoles