Luminescent substance and illuminating device

Abstract

A luminophore may have the general empirical formula X.sub.3A.sub.7Z.sub.3O.sub.11:E, where: X=Mg, Ca, Sr, Ba, and/or Zn; A=Li, Na, K, Rb, Cs, Cu, and/or Ag; Z=Al, Ga, and/or B; and E=Eu, Ce, Yb, and/or Mn.

Claims

1. A phosphor having the general empirical formula X.sub.3A.sub.7Z.sub.3O.sub.11:E, wherein: X=Mg, Ca, Sr, Ba, Zn, or combinations thereof; A=Li, Na, K, Rb, Cs, Cu, Ag, or combinations thereof; Z=Al, Ga, B, or combinations thereof; and E=Eu, Ce, Yb, Mn, or combinations thereof.

2. The phosphor as claimed in claim 1, wherein: X=Mg, Ca, Sr, and/or Ba; A=Li, Na, K, Rb, Cs, Cu, Ag, or combinations thereof; Z=Al, Ga, B, or combinations thereof; and E=Eu, Ce, Yb, Mn, or combinations thereof.

3. The phosphor as claimed in claim 1, wherein the general empirical formula is (Ba.sub.1-xX*.sub.x).sub.3A.sub.7Z.sub.3O.sub.11:E, wherein: X*=Mg, Ca, Sr, or combinations thereof; A=Li, Na, K, Rb, Cs, Cu, Ag, or combinations thereof; Z=Al, Ga, B, or combinations thereof; E=Eu, Ce, Yb, Mn, or combinations thereof; and 0≤x≤1.

4. The phosphor as claimed in claim 3, wherein: X*=Mg, Ca, Sr, or combinations thereof; A=Li, Na, K, Rb, Cs, or combinations thereof; Z=Al, Ga, B, or combinations thereof; and E=Eu, Ce, Yb, Mn, or combinations thereof and 0≤x=0.25.

5. The phosphor as claimed in claim 3, wherein the general empirical formula is (Ba.sub.1-xX*.sub.x).sub.3A.sub.7(Al.sub.1-yGa.sub.y).sub.3O.sub.11:E, wherein: X*=Mg, Ca, Sr, or combinations thereof; A=Li, Na, K, Rb, Cs, or combinations thereof; E=Eu, Ce, Yb, Mn, or combinations thereof; 0≤y≤1 and 0≤x≤1.

6. The phosphor as claimed in claim 1; wherein the general empirical formula is Ba.sub.3A.sub.7Al.sub.3O.sub.11:E, wherein: A=Li, Na, K, Rb, Cs, or combinations thereof; and E=Eu, Ce, Yb, Mn, or combinations thereof.

7. The phosphor as claimed in claim 1 wherein the general empirical formula is Ba.sub.3Li.sub.7Al.sub.3O.sub.11:E, wherein: E=Eu, Ce, Yb, Mn, or combinations thereof.

8. The phosphor as claimed in claim 1, wherein E=Eu.

9. The phosphor as claimed in claim 1, wherein the phosphor crystallizes in a cubic crystal system.

10. The phosphor as claimed in claim 1, wherein the phosphor crystallizes in a in the cubic space group Fm 3 m.

11. An illumination device comprising a phosphor as claimed in claim 1.

12. The illumination device as claimed in claim 11, wherein: a semiconductor layer sequence configured to emit electromagnetic primary radiation; and a conversion element comprising the phosphor; and wherein the conversion element at least partly converts the electromagnetic primary radiation into electromagnetic secondary radiation.

13. The illumination device as claimed in claim 12, wherein the conversion element further comprises: a second phosphor configured to emit radiation in the green region of the spectrum; and a third phosphor configured to emit radiation in the orange-red region of the spectrum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantageous embodiments and developments arise from the working examples described below in conjunction with the figures. The accompanying drawings serve to afford an understanding of various embodiments. The drawings illustrate embodiments and together with the description serve to elucidate same. Further embodiments and numerous advantages from among those intended are evident directly from the following detailed description. The elements and structures shown in the drawings are not necessarily illustrated in a manner true to scale with respect to one another. Identical reference signs refer to identical or mutually corresponding elements and structures.

(2) FIGS. 1 and 2 show emission spectra.

(3) FIGS. 3A, 3B, 3C show sections of the crystal structure of the phosphor.

(4) FIGS. 4, 5, and 6 show conversion LEDs.

DETAILED DESCRIPTION

(5) FIG. 1 shows the emission spectrum of Ba.sub.3Li.sub.7Al.sub.3O.sub.11:Eu (WE1). The wavelength in nanometers is plotted on the x axis and the intensity in percent on the y axis. The phosphor has a peak wavelength of about 490 nm and a full width at half maximum of about 45 nm. To measure the emission spectrum, the phosphor was excited in parallel with primary radiation having a peak wavelength of 405 and 440 nm. The phosphor may be present as the sole phosphor in an illumination device or conversion LED that in full conversion emits overall radiation in the blue-green region of the electromagnetic spectrum or in partial conversion emits overall radiation in the blue to blue-green region of the electromagnetic spectrum. The illumination device or conversion LED that in partial conversion emits overall radiation in the blue to blue-green region of the electromagnetic spectrum is suitable, for example, for signal lights such as blue lights for e.g. police cars, ambulances, emergency medical vehicles or fire engines. Although an illumination device or conversion LED comprising the phosphor Ba.sub.3Li.sub.7Al.sub.3O.sub.11:Eu is able to create the same or similar color impression compared to a blue-emitting semiconductor chip, in other words have the same or very similar CIEx and CIEy values in the CIE color space, the overall radiation is slightly longer-wavelength (with a slightly larger component in the green region of the spectrum) and thereby achieves greater overlap with the eye sensitivity curve. This results in higher eye sensitivity. This means that the color of the overall radiation is perceived by the human eye more clearly and more intensely.

(6) FIG. 2 shows emission spectra of the phosphor WE1 and of a comparative example CE1 Ca.sub.8Mg(SiO.sub.4).sub.4Cl.sub.2:Eu. In addition, FIG. 2 shows the melanopic sensitivity curve M. The melanopic sensitivity curve M shows the wavelengths with which melatonin production in the body can best be suppressed. As can be seen, the emission spectrum of WE1 shows appreciably higher overlap with the melanopic sensitivity curve M than does the emission spectrum of CE1. With the phosphor, it is thus possible to generate melanopic light that may be used to effectively suppress melatonin formation. If a person is exposed to the radiation of an illumination device that comprises the phosphor WE1, this can advantageously result in heightened alertness or increased ability to concentrate. Illumination devices comprising the phosphor can thus be used for room lighting, in particular for “human centric lighting” applications.

(7) FIGS. 3A, 3B, and 3C each show a section from the crystal structure of the phosphor Ba.sub.3Li.sub.7Al.sub.3O.sub.11:Eu.

(8) FIG. 3A shows a section of the crystal structure in the direction of view along the face diagonals [011]. The hatched triangles are LiO.sub.4 or AlO.sub.4 tetrahedra, in which Li or Al are present in the centers and oxygen at the corners of the tetrahedra.

(9) FIG. 3B shows a section of the crystal structure in the direction of view along the face diagonals [011]. The hatched triangles are LiO.sub.4 or AlO.sub.4 tetrahedra, in which Li or Al are present in the centers and oxygen at the corners of the tetrahedra. In comparison to FIG. 3A, in FIG. 3B the Ba atoms are not shown.

(10) FIG. 3C shows a section of the crystal structure in the direction of view of the space diagonals [111]. The hatched triangles are LiO.sub.4 or AlO.sub.4 tetrahedra, in which Li or Al are present in the centers and oxygen at the corners of the tetrahedra.

(11) The crystal structure is made up of corner- and edge-linked LiO.sub.4 or AlO.sub.4 tetrahedra. These form two interpenetrating supratetrahedra, each of which is made up of LiO.sub.4 and AlO.sub.4 tetrahedra that are linked at their corners on all sides Six LiO.sub.4 and six AlO.sub.4 tetrahedra in each case form the edge of a supratetrahedron. These interpenetrating supratetrahedra are then linked with other supratetrahedra at their corners to form a network in space. The oxygen atom with the designation O005 at Wyckoff position 4b (Table 3) is the sole oxygen atom that is not involved in this network of tetrahedra. Instead, it is located at the center of an octahedron made up of Ba atoms outside the supratetrahedra. The Ba atoms are in turn each surrounded by nine oxygen atoms at distances of between 273.7 pm and 311.0 pm in a tridecahedral arrangement to form a twisted elongated square pyramid.

(12) FIGS. 4 to 6 each show schematic side views of different embodiments of the illumination devices described here, in particular conversion LEDs.

(13) The conversion LEDs in FIGS. 4 to 6 include at least one phosphor described herein. In addition, one further phosphor or a combination of phosphors may be present in the conversion LED. The additional phosphors are known to the those skilled in the art and are therefore not mentioned explicitly at this point.

(14) The conversion LED depicted in FIG. 4 has a semiconductor layer sequence 2 disposed atop a substrate 10. The substrate 10 may, for example, be designed to 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) which, when the conversion LED is in operation, emits primary radiation having a wavelength of 330 nm and 450 nm inclusive. The conversion element 3 is positioned in the beam path of the primary radiation S. The conversion element 3 comprises a matrix material, for example a silicone, epoxy resin or hybrid material, and particles of the phosphor 4.

(15) For example, the phosphor 4 has an average particle size of 10 μm. When the conversion LED is in operation, the phosphor 4 is capable of converting the primary radiation S at least partly or fully into secondary radiation SA in the blue-green region of the spectrum. In the conversion element 3, the phosphor 4 is distributed homogeneously in the matrix material within the manufacturing tolerance.

(16) Alternatively, the phosphor 4 may also be distributed in the matrix material with a concentration gradient.

(17) Alternatively, the matrix material may also be absent, such that the phosphor 4 takes the form of a ceramic converter.

(18) The conversion element 3 has been applied over the full area of the radiation exit face 2a of the semiconductor layer sequence 2 and of the side faces of the semiconductor layer sequence 2, and is in direct mechanical contact with the radiation exit face 2a of the semiconductor layer sequence 2 and the side faces of the semiconductor layer sequence 2. The primary radiation S may also exit via the side faces of the semiconductor layer sequence 2.

(19) The conversion element 3 may be applied, for example, by injection molding, injection compression molding or spray coating methods. In addition, the conversion LED has electrical contacts (not shown here), the formation and disposition of which are known to those skilled in the art.

(20) Alternatively, it is also possible for the conversion element to have been prefabricated and applied to the semiconductor layer sequence 2 by means of a “pick-and-place” process.

(21) FIG. 5 shows a further working example of a conversion LED 1. The conversion LED 1 has a semiconductor layer sequence 2 atop a substrate 10. The conversion element 3 has been formed atop the semiconductor layer sequence 2. The conversion element 3 takes the form of platelets. The platelet may consist of particles of the inventive 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.

(22) The conversion element 3 has been applied over the full area of the radiation exit face 2a of the semiconductor layer sequence 2. More particularly, no primary radiation S exits via the side faces of the semiconductor layer sequence 2; rather, it exits predominantly via the radiation exit face 2a. The conversion element 3 may have been applied atop the semiconductor layer sequence 2 by means of a bonding layer (not shown), composed for example of silicone.

(23) The conversion LED 1 depicted in FIG. 6 has a housing 11 with a recess. A semiconductor layer sequence 2 having an active layer (not shown) is disposed within the recess. When the conversion LED is in operation, the active layer emits primary radiation S with a wavelength of 330 nm to 450 nm inclusive.

(24) The conversion element 3 takes the form of an encapsulation of the layer sequence in the recess and comprises a matrix material, for example a silicone, and a phosphor 4, for example Ba.sub.3Li.sub.7Al.sub.3O.sub.11:Eu. When the conversion LED 1 is in operation, the phosphor 4 converts the primary radiation S at least partly into secondary radiation SA. Alternatively, the phosphor converts the primary radiation S fully into secondary radiation SA.

(25) It is also possible that the phosphor 4 in the working examples in FIGS. 4 to 6 is arranged in the conversion element 3 spaced apart from the semiconductor layer sequence 2 or the radiation exit face 2a. This may be achieved for example by sedimentation or by applying the conversion layer atop the housing.

(26) For example, by contrast with the embodiment depicted in FIG. 6, the encapsulation may consist solely of a matrix material, for example silicone, with application, atop the encapsulation, spaced apart from the semiconductor layer sequence 2, of the conversion element 3 as a layer atop the housing 11 and atop the encapsulation.

(27) The working examples and features thereof that have been described in conjunction with the figures may in further working examples also be combined with one another, even when 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 in accordance with the description in the general part.

(28) This patent application claims the priority of German patent application 10 2018 004 751.3, the disclosure content of which is hereby incorporated by reference.

LIST OF REFERENCE SIGNS

(29) 1 Illumination device or conversion LED 2 Semiconductor layer sequence or semiconductor chip 2a Radiation exit face 3 Conversion element 4 Phosphor 10 Substrate 11 Housing S Primary radiation SA Secondary radiation LED Light-emitting diode λ.sub.dom Dominant wavelength λ.sub.peak Peak wavelength ppm Parts per million WE Working example CE Comparative example g Gram I Intensity mol % Mole percent nm Nanometer ° C. Degree Celsius