Conversion LED with high color rendition index

Abstract

Conversion LED emits primary radiation (peak wavelength 435 nm to 455 nm) and has a luminescent substance-containing layer positioned to intercept the primary radiation and convert it into secondary radiation. First and second luminescent substances are used. The first luminescent substance is a A.sub.3B.sub.5O.sub.12:Ce garnet type emitting yellow green having cation A=75 to 100 mol. % Lu, remainder Y and a Ce content of 1.5 to 2.9 mol. %, where B=10 to 40 mol. % Ga, remainder Al. The second luminescent substance is of the MAlSiN.sub.3:Eu calsine type which emits orange red, where M is Ca alone or at least 80% Ca and the remainder of M may be Sr, Ba, Mg, Li or Cu, in each case alone or in combination, wherein some of the Al up to 20%, can be replaced by B, and wherein N can be partially replaced by O, F, Cl, alone or in combination.

Claims

1. A conversion LED comprising: a chip which emits primary radiation; and a luminescent substance-containing layer which is on the chip or positioned so that it intercepts the primary radiation emitted from the chip and which converts at least some of the primary radiation of the chip into secondary radiation, wherein the luminescent substance-containing layer comprises a first luminescent substance of the A.sub.3B.sub.5O.sub.12:Ce garnet type which emits yellow green and a second luminescent substance of the MAlSiN.sub.3:Eu calsine type which emits orange red, the peak wavelength of the primary radiation lies in the 435 nm to 455 nm range, the first luminescent substance is a garnet having essentially the cation A=75 to 100 mol. % Lu, remainder Y and a Ce content of 1.5 to 2.9 mol. %, where B=10 to 40 mol. % Ga, remainder Al, the second luminescent substance is of the basic MAlSiN.sub.3:Eu type, where M is Ca alone or at least 80% Ca and the remainder of M is Sr, Ba, Mg, Li or Cu, in each case alone or in combination, wherein some of the Al up to 20%, can be replaced by B, and wherein N is optionally partially replaced by O, F, Cl, alone or in combination, and the conversion LED emits mixed light of primary light and secondary light, said mixed light having a CRI between 96 and 98 with good red rendering with R9=90 to 99.

2. The conversion LED as claimed in claim 1, wherein the second luminescent substance contains Ca alone as component M.

3. The conversion LED as claimed in claim 1, wherein the second luminescent substance contains 0.2 to 1.3 mol.-% Eu as doping which is attributed to the component M.

4. The conversion LED as claimed in claim 1, wherein the second luminescent substance is CaAlSiN.sub.3:Eu with 0.3 to 0.8% Eu fraction of M.

5. The conversion LED as claimed in claim 1, wherein the first luminescent substance is A.sub.3B.sub.5O.sub.12, where A=80 to 100% Lu, remainder Y and a Ce content of 1.5 to 2.5%, where B=15 to 25% Ga, remainder Al.

6. The conversion LED as claimed in claim 1, wherein said M contains is at least 95% Ca, and wherein at most 5% of the Al can be replaced by B.

7. The conversion LED as claimed in claim 1, wherein in the case of the component B the first luminescent substance contains 20 to 30 mol.-% Ga, the remainder being Al.

8. The conversion-LED of claim 1, wherein the first luminescent substance has a full width at half maximum between 104.3 nm and 113 nm and the second luminescent substance has a full width at half maximum between 86.7 nm and 104.4 nm.

9. A conversion LED comprising: a chip which emits primary radiation; and a luminescent substance-containing layer which is on the chip or positioned so that it intercepts the primary radiation emitted from the chip and which converts at least some of the primary radiation of the chip into secondary radiation, wherein the luminescent substance-containing layer comprises a first luminescent substance of the A.sub.3B.sub.5O.sub.12:Ce garnet type which emits yellow green and a second luminescent substance of the MAlSiN.sub.3:Eu calsine type which emits orange red, wherein the peak wavelength of the primary radiation lies in the 435 nm to 455 nm range, the first luminescent substance being a garnet having essentially the cation A=75 to 100 mol. % Lu, remainder Y and a Ce content of 1.5 to 2.9 mol. %, where B=10 to 40 mol. % Ga, remainder Al, the second luminescent substance is of the basic MAlSiN.sub.3:Eu type, where M is Ca alone or at least 80% Ca and the remainder of M is Sr, Ba, Mg, Li or Cu, in each case alone or in combination, wherein some of the Al up to 20%, can be replaced by B, and wherein N is optionally partially replaced by O, F, Cl, alone or in combination, and, wherein the conversion LED emits warm-white light with a color temperature between 2900 K to 3150 K.

10. The conversion LED of claim 9, wherein the color temperature of the emitted light lies between 2900 K and 3100 K.

11. The conversion LED as claimed in claim 9, wherein the first luminescent substance contains 1.8% to 2.6 mol.-% Ce as doping which is attributed to the component A, the remainder being A.

12. The conversion LED as claimed in claim 9, wherein the second luminescent substance contains 0.3 to 0.9 mol.-% Eu as doping which is attributed to the component M.

13. A conversion LED comprising: a chip which emits primary radiation; and a luminescent substance-containing layer which is on the chip or positioned so that it intercepts the primary radiation emitted from the chip and which converts at least some of the primary radiation of the chip into secondary radiation, wherein the luminescent substance-containing layer comprises a first luminescent substance of the A.sub.3B.sub.5O.sub.12:Ce garnet type which emits yellow green and a second luminescent substance of the MAlSiN.sub.3:Eu calsine type which emits orange red, wherein the peak wavelength of the primary radiation lies in the 435 nm to 455 nm range, wherein the luminescent substance is a garnet having essentially the cation A=75 to 100 mol. % Lu, remainder Y and a Ce content of 1.5 to 2.9 mol. %, where B=10 to 40 mol. % Ga, remainder Al, wherein the second luminescent substance is of the basic MAlSiN.sub.3:Eu type, where M is Ca alone or at least 80% Ca and the remainder of M is Sr, Ba, Mg, Li or Cu, in each case alone or in combination, wherein some of the Al up to 20%, can be replaced by B, and wherein N is optionally partially replaced by O, F, Cl, alone or in combination, and wherein the conversion LED emits warm-white light with a color temperature between 3000 K to 3050 K.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention shall be explained in more detail below with reference to a number of exemplary embodiments. In the figures:

(2) FIG. 1 shows a conversion LED;

(3) FIG. 2 shows a comparison of the temperature dependence of various red-emitting luminescent substances;

(4) FIG. 3 shows a comparison of the temperature dependence of various green-emitting luminescent substances;

(5) FIG. 4 shows a comparison of the time dependence of the converter losses for various luminescent substances;

(6) FIG. 5 shows a comparison of the CRI for various luminescent substance mixtures with primary excitation wavelength shifting;

(7) FIG. 6 shows a comparison of the R9 for various luminescent substance mixtures with primary excitation wavelength shifting;

(8) FIG. 7 shows a comparison of the overall emission of a conversion LED with various primary emissions;

(9) FIGS. 8-10 show a comparison of the emission of LuAGaG and YAGaG and mixed sion with different peak position of the primary emission (Ex);

(10) FIG. 11 shows an LED module with remotely attached luminescent substance mixture;

(11) FIG. 12 shows a comparison of the emission in the case of calsines containing O;

(12) FIG. 13 shows a comparison of the emission in the case of calsines containing Cl;

(13) FIG. 14 shows a comparison of the emission in the case of calsines containing F;

(14) FIG. 15 shows a comparison of the emission in the case of calsines containing Cu;

(15) FIG. 16 shows a comparison of the emission in the case of calsines containing different proportions of Eu;

(16) FIG. 17 shows a comparison of the emission in the case of Lu garnets containing different proportions of Y.

DETAILED DESCRIPTION OF THE DRAWINGS

(17) FIG. 1 shows the structure of a conversion LED for RGB-based white light as known per se. The light source is a semiconductor component having an InGaN-type blue-emitting chip 1 with a peak emission wavelength of 435 to 455 nm peak wavelength, for example, 445 nm, which is embedded in a light-tight basic package 8 in the region of a recess 9. The chip 1 is connected via a bonding wire 14 to a first terminal 3 and directly to a second electrical terminal 2. The recess 9 is filled with a potting compound 5 containing as its principal constituents a silicon (60-90 weight %) and luminescent substance pigments 6 (less than 40 weight %). A first luminescent substance is a green-emitting garnet luminescent substance LuAGaG:Ce, another a red-emitting alumonitride silicate CaAlSiN.sub.3:Eu. The recess has a wall 17 which serves as a reflector for the primary and secondary radiation from the chip 1 or, more specifically, the pigments 6.

(18) FIG. 2 shows the thermal quenching characteristics of various red-emitting luminescent substances which in principle can be readily excited by means of the chip from FIG. 1. The new deep-red luminescent substance CaAlSiN.sub.3:Eu or (Ca.sub.1-xEux)AlSiN.sub.3 is characterized by very low thermal quenching, with a fraction of 0.3% (x=0.003) to 0.8% Eu (x=0.008) being particularly well suited. An Eu fraction of M=Ca of x=0.002-0.012 is generally preferred, particularly preferably x=0.003-0.009. It is characterized by very low thermal quenching (see curve 1). The graph shows a comparison with other orange/red luminescent substances. Nitridosilicates containing Ba or Ca are much less suitable (see curves 2 and 3). Orthosilicates are not suitable (see curve 4). The luminescent substance CaAlSiN.sub.3:Eu (CIE color coordinates where x/y=0.657/0.341) can usually be modified in multifarious ways for special requirements without significant changes in emission. In this case Ca can be replaced in small fractions up to 20%, in particular up to 10%, by Ba, Sr, Mg, Li or Cu alone or in combination. This applies similarly to the Al fraction, which can be replaced in small amounts, in particular up to 10%, by B.

(19) An example of a modified luminescent substance (Ca.sub.0.892Mg.sub.0.1Eu.sub.0.008) (Al.sub.0.99B.sub.0.01)Si.sub.1N.sub.3 (CIE x/y=0.657/0340) of the basic structure type CaAlSiN.sub.3:Eu is given in Table 3. Further modifications with slightly altered cation ratio or partial CaSr substitution possibly in combination with a partial O/N substitutionsuch as e.g. (Ca.sub.0.945Sr.sub.0.045Eu.sub.0.01)AlSi(N.sub.2.9O.sub.0.1)are also possible.

(20) FIG. 3 shows the thermal quenching characteristics of various yellow-green-emitting luminescent substances which in principle can be readily excited by means of the chip from FIG. 1. The luminescent substance A.sub.3B.sub.5O.sub.12:Ce in the embodiment variant with the preferred composition LuAGaG, i.e. Lu.sub.3(Al,Ga).sub.5O.sub.12:Ce with approx. 25% Ga fraction for component B (10-40% Ga is preferred, 15-30% Ga being particularly preferred) and approx. 2.2% Ce (1.5-2.9% Ce is preferred, 1.8-2.6% Ce being particularly preferred, in each case referred to the fraction A), is characterized by very low thermal quenching. A preferred luminescent substance is (Lu.sub.0.978Ce.sub.0.022).sub.3Al.sub.3.75Ga.sub.1.25O.sub.12, (see curve 1). The graph shows a comparison with other yellow and green luminescent substances which exhibit considerably poorer thermal quenching behavior. Orthosilicates (see curves 3,4) are totally unsuitable, but YAGaG, i.e. Y.sub.3(Al,Ga).sub.5O.sub.12:Ce according to curve 2, is also considerably poorer.

(21) FIG. 4 shows the stability of the yellow-green component. The stability of the green luminescent substance with the preferred composition LuAGaG with approx. 25% Ga and approx. 2.2% Ce, ((Lu.sub.0.978Ce.sub.0.022).sub.3Al.sub.3.75Ga.sub.1.25O.sub.12) was determined in an LED aging test and compared with other known yellow/green-emitting luminescent substances. In the test a high-power blue LED (?.sub.peak=435 nm) was encapsulated in silicon with a dispersion of the respective luminescent substance and driven at 350 mA for 1000 h. The relative intensities of the blue LED peak and of the luminescent substance peak were measured at the start and at the end of the test and the loss of conversion efficiency determined therefrom. This LuAGaG luminescent substance is perfectly stable (square measurement points) within the bounds of the measurement errors, whereas under comparable conditions an orthosilicate will exhibit clear signs of aging (round measurement points).

(22) The color rendering index of the warm white LED having the novel luminescent substance mixture according to the invention (LuAGaG plus deep-red CaAlSiN.sub.3) shows a small dependence on the exciting blue LED wavelength used. A shift in the peak wavelength by 9 nm produces a CRI loss (Ra8) of only 3 points in the color rendering index. Other typical mixtures lose 5 points already with a difference of 7 nm peak wavelength in the blue (see Table 1). In order then to reduce the CRI loss there to 1 point it is necessary to add a third luminescent substance, which has a negative impact on efficiency and color steering. The dependence of the color rendering index on saturated red in particular is also very severely reduced, as is made apparent by the discrete value for R9.

(23) Tab. 1 shows for the last two samples that excellent CRI values, namely Ra8 is at least 94 and the red index R9, at least 90, are possible in the 435 nm to 445 nm peak wavelength range of the exciting LED at a color temperature von 3000 to 3100 K.

(24) TABLE-US-00001 TABLE 1 Peak Luminescent wavelength substance 1 Luminescent Luminescent of the blue Color (green- substance 2 substance 3 Ratio LED/nm temperature/K yellow) (orange-red) (blue-green) yellow:red CRI Ra8 R9 462 3200 YAG:3% Ce (Sr,Ca).sub.2Si.sub.5N.sub.8:Eu 9:1 81 23 (60% Sr) 455 3250 YAG:3% Ce (Sr,Ca).sub.2Si.sub.5N.sub.8:Eu 10.3:1 76 8 (60% Sr) 455 3200 YAG:3% Ce (Sr,Ca).sub.2Si.sub.5N.sub.8:Eu green chloro- 9:1 80 25 (60% Sr) silicate 462 3250 YAGaG:4% Ce (Sr,Ca).sub.2Si.sub.5N.sub.8:Eu 6.1:1 86 43 (25% Ga) (60% Sr) 455 3250 YAGaG:4% Ce (Sr,Ca).sub.2Si.sub.5N.sub.8:Eu 7:1 83 34 (25% Ga) (60% Sr) 444 3200 YAGaG:4% Ce (Sr,Ca).sub.2Si.sub.5N.sub.8:Eu 7:1 77 20 (25% Ga) (60% Sr) 444 3050 LuAGaG:2.2% CaAlSiN.sub.3:Eu 3.35:1 97 96 Ce (25% Ga) 435 3025 LuAGaG:2.2% CaAlSiN.sub.3:Eu 2:1 94 96 Ce (25% Ga)

(25) FIGS. 5 and 6 show the color rendering index (CRI) Ra8 and the red index R9 for various systems. The color rendering index of the warm white LED having the novel luminescent substance mixture according to the invention (LuAGaG+deep-red CaAlSiN.sub.3) shows only a slight dependence on the LED wavelength used. A shift in the blue wavelength by 9 nm produces a CRI loss of 3 points only. Other typical mixes lose 5 points already with a difference of 7 nm in blue wavelength (see Table 1). In order to reduce the CRI loss to 1 point it is necessary to add a third luminescent substance, which has a negative impact on efficiency and color steering.

(26) In particular the dependence of the color rendering index on saturated red is also very greatly reduced, as is made apparent by the discrete value for R9 (see FIG. 6).

(27) FIG. 7 explains the cause for the low dependence of the color rendering index CRI on the blue wavelength: In the system according to the invention the luminescent substance emission shifts surprisingly with increasingly shortwave excitation wavelength clearly toward short wavelengths (see the region at about 530 nm. This results in a certain compensation in the overall spectrum: The blue-green fractions that are missing when an LED emitting at shorter wavelengths is used are virtually balanced out by the stronger blue-green fractions of the shifted luminescent substance emission.

(28) FIG. 8 shows the relative intensity in the case of a shift of the luminescent substance spectrum of the green-yellow luminescent substance with variable excitation wavelength between 430 and 470 nm (Ex430 to 470) compared with YAGaG:Ce (FIG. 9) and yellow (Sr,Ba)Si.sub.2O.sub.2N.sub.2:Eu (FIG. 10).

(29) Surprisingly, the novel green LuAGaG garnet behaves in a significantly different manner to the comparative luminescent substances. It exhibits a strong green shift with declining excitation wavelength. The comparative luminescent substances remain roughly constant. The emission spectra of the three luminescent substances are shown in comparison in the range of excitation by means of a LED with peak wavelength between 430 and 470 nm that is relevant to LED applications. The curves in FIG. 10 all overlay one another so closely that practically only one curve can be seen.

(30) The use of a lutetium garnet has a significantly positive impact overall on the color rendering index. Compared with yttrium garnets with similar luminescent substance emission wavelength, much higher color rendering index values Ra8 and R9 are obtained with LuAGaG (see Table 2). As a result of this and by virtue of the good excitability at short wavelengths it is possible for the first time to use high-efficiency shortwave blue LEDs for warm white conversion LEDs for a color temperature of 2900 to 3150 K.

(31) TABLE-US-00002 TABLE 2 Peak wavelength of Luminescent R9 the blue Color Luminescent substance 1 substance 2 Ratio (deep LED/nm temperature/K (green-yellow) (orange-red) yellow:red Ra8 red) 444 3050 YAGaG:40% Ga, 2% Ce CaAlSiN.sub.3:Eu 2.3:1 95 82 444 3000 LuAGaG:2.2% Ce, 25% CaAlSiN.sub.3:Eu 2.55:1 98 96 Ga 444 3050 LuAGaG:2.2% Ce, 25% CaAlSiN.sub.3:Eu 3.6:1 98 99 Ga

(32) A very high color rendering index is achieved with just two luminescent substances, despite shortwave blue LED in the 435 to 455 nm range. In this case the special tuning of the two chosen luminescent substances to each other is important. For example, the use of a red luminescent substance of the nitridosilicate type emitting at an even longer wavelength does not increase the CRI value or the value for the red rendering R9, but yields poorer values. The use of Y garnets does not lead to the sort of high values that can be realized with Lu garnet. Details of various mixtures can be found in Tab. 3. Gd is totally unsuitable as a principal component and should, like Tb or La, be added to the component A at best in small amounts up to 5 mol.-% for fine tuning. In contrast, a Y fraction of up to approx. 30%, preferably with a fraction of 10 to 25%, makes a good addition to Lu. The cause is the relatively similar ionic radius of Lu and Y. However, higher values of Y would shift the emission of the luminescent substance back into a range which would adversely affect the desired performance of the overall system.

(33) TABLE-US-00003 TABLE 3 Comparison of various luminescent substance mixtures at approx. 3000 K (preferred solutions in bold); Peak stands for peak wavelength of the blue LED (nm); R9 denotes saturated red. Color Luminescent substance 1 Ratio Peak nm temperature/K (green-yellow) Luminescent substance 2 (red) yellow:red Ra8 R9 444 3050 YAGaG:40% Ga, 2% Ce Ca.sub.0.94Eu.sub.0.02Li.sub.0.045A.sub.l3.8Si.sub.8.2N.sub.18 2.2:1 89 66 444 3000 YAGaG:40% Ga, 2% Ce Sr.sub.1.14Ca.sub.0.74Eu.sub.0.12Si.sub.5N.sub.8 9.4:1 89 62 444 3000 YAGaG:40% Ga, 2% Ce Ca.sub.0.992Eu.sub.0.008AlSiN.sub.3 3:1 94 83 444 3050 YAGaG:40% Ga, 2% Ce Sr.sub.0.76Ba.sub.0.96Ca.sub.0.16Eu.sub.0.12Si.sub.5N.sub.8N.sub.8 9:1 84 32 444 3050 YAGaG:40% Ga, 2% Ce Ca.sub.0.992Eu.sub.0.008AlSiN.sub.3 2.3:1 95 82 444 3000 LuAGaG:2.5%% Ce, 25% Ca.sub.0.992Eu.sub.0.008AlSiN.sub.3 2.55:1 98 96 Ga 444 3050 LuAGaG:2.2% Ce, 25% Ga Ca.sub.0.992Eu.sub.0.008AlSiN.sub.3 3.6:1 98 99 435 3025 LuAGaG:2.2% Ce, 25% Ga Ca.sub.0.992Eu.sub.0.008AlSiN.sub.3 2:1 94 96 444 3000 LuAGaG:2.2% Ce, 25% Ga Ca.sub.0.892Mg.sub.0.1Eu.sub.0.008Al.sub.0.99B.sub.0.01Si.sub.1N.sub.3 2:1 97 94

(34) In principle it is possible to use the luminescent substance mixture as a dispersion, as a thin film, etc. directly on the LED or else, as known per se, on a separate carrier positioned upstream of the LED. FIG. 11 shows such a module 20 with various LEDs 24 on a baseplate 21. Over it is mounted a package with side walls 22 and a cover plate 12. The luminescent substance mixture is applied here as a layer 25 both on the side walls and above all on the cover plate 23, which is transparent.

(35) In principle it is not precluded that the garnet according to the invention, in addition to having predominantly Lu as principal component, also includes fractions of Y as cation A. These should be in the range of up to 32% at maximum. Other cations such as Tb, La, etc. are not categorically ruled out as additives, but due to their lack of conformance with the system (Lu, Y) should only be used in small amounts, preferably max. 5% of A, for any special-purpose adaptations of the properties of the luminescent substance.

(36) Suitable modified calsines are shown in Tab. 4. This relates to systems that originate from the basic system CaAlSiN.sub.3:Eu. In this case the elements O, F, Cl can replace a percentage of the N, while the element Cu can replace a percentage of Ca.

(37) FIG. 12 shows emission spectra for various calsines in which N is partially replaced by small amounts of O (see Tab. 4). In order not to widen the full width at half maximum too severely, the O fraction should preferably not exceed 0.2 mol.-%.

(38) FIG. 13 shows emission spectra for various calsines in which N is partially replaced by small amounts of Cl (see Tab. 4). In order not to widen the full width at half maximum too severely, the Cl fraction should preferably not exceed 0.05 mol.-%.

(39) FIG. 14 shows emission spectra for various calsines in which N is partially replaced by small amounts of F (see Tab. 4). In order not to widen the full width at half maximum too severely, the F fraction should preferably not exceed 0.05 mol.-%.

(40) FIG. 15 shows emission spectra for various calsines in which Ca is partially replaced by small amounts of Cu (see Tab. 4). This allows a shift toward shorter wavelengths to be achieved. In order to prevent efficiency losses becoming too great due to lattice distortions, the Cu fraction should preferably not exceed 0.05 mol.-%. The production process is successful here in the following way:

(41) TABLE-US-00004 TABLE 5 Production of Cu-containing calsines (sample 236) S236 Substance Element Atomic ratio Initial weight Ca.sub.3N.sub.2 Ca 0.983 10.537 g CuF.sub.2 Cu 0.012 0.238 g Si.sub.3N.sub.4 Si 1.000 10.143 g AlN Al 1.000 8.891 g Eu.sub.2O.sub.3 Eu 0.005 0.191 g Total sample weight 30.000 g

(42) All the starting materials are weighed out inside the glovebox and homogenized for six hours in a planetary mill. The mixture is loosely filled into a tightly closing crucible made of molybdenum and transferred to a high-temperature tubular furnace.

(43) The annealing is carried out under a flowing nitrogen atmosphere (2 l/min). The sample is heated at a rate of 250 K/h to 1600? C., held at that temperature for four hours and cooled down to room temperature likewise at 250 K/h.

(44) The resulting annealed cake is milled in a mortar mill and screened through a 30 ?m gauze. The screened material is filled back into the crucible and annealed once more in a similar manner to the first annealing.

(45) The resulting annealed cake is milled in a mortar mill and screened through a 30 ?m gauze. The screened material is the luminescent substance S 236.

(46) The production of calsine as sample S176 is shown in Tab. 6.

(47) TABLE-US-00005 TABLE 6 Production of calsine (sample 176) S176 Substance Element Atomic ratio Initial weight Ca.sub.3N.sub.2 Ca 1.000 17.899 g Si.sub.3N.sub.4 Si 1.000 16.937 g AlN Al 1.000 14.846 g Eu.sub.2O.sub.3 Eu 0.005 0.319 g Total sample weight 50.000 g

(48) All the starting materials are weighed out inside the glovebox and homogenized in a planetary mil for six hours I. The mixture is loosely filled into a tightly closing crucible made of molybdenum and transferred to a high-temperature tubular furnace.

(49) The annealing is carried out under a flowing nitrogen atmosphere. The sample is heated at a rate of 250 K/h to 1600? C., held at that temperature for four hours and cooled down to room temperature likewise at 250 K/h.

(50) The resulting annealed cake is milled in a mortar mill and screened through a 30 ?m gauze. The screened material is filled back into the crucible and annealed once more in a similar manner to the first annealing.

(51) The resulting annealed cake is milled in a mortar mill and screened through a 30 ?m gauze. The screened material is the luminescent substance S176.

(52) FIG. 16 shows emission spectra for various calsines in which the percentage of the activator Eu has been varied. It is apparent that the emission shifts toward shorter wavelengths, the smaller the chosen concentration of activator. In this case it lies between 0.3 and 0.5 mol.-%.

(53) Tab. 7 shows various garnets from the A.sub.3B.sub.5O.sub.12:Ce system, where A is chosen from (Lu, Y). It is demonstrated here that good values can be achieved for A=Lu up to A=70% Lu, remainder Y. At the same time the ratio between Al and Ga must be chosen carefully for component B. The Ga fraction should be between 10 and 40 mol.-%, in particular 10 to 25%. Various A.sub.3B.sub.5O.sub.12:Ce (Lu,Y) garnets are shown in Tab. 7, the concentration of the activator Ce being 2% of A in each case and the chosen ratio is A=Lu,Y (the Lu fraction is specified, remainder is Y) and B=Al,Ga (the Ga fraction is specified, remainder is Al).

(54) FIG. 17 shows emission spectra for various garnets in which the percentage of Y has been varied. It is apparent that the emission remains virtually constant for small Y fractions.

(55) Tab. 8 shows pure LuAGAG luminescent substances with incremental increases in Ga percentage. These table values, as of the other tables also, basically relate always to a reference excitation at 460 nm.

(56) TABLE-US-00006 TABLE 8 A.sub.3B.sub.5O.sub.12:Ce Lu(Al,Ga) garnets (called LuAGAG) Sample Fraction Lu, Fraction Ga, Lambda_dom/ FWHM/ number remainder Y remainder Al x y nm nm rel. QE SL 315c/08 100% 5.0% 0.350 0.567 557.5 109.1 1.00 SL 005c/09 100% 15.0% 0.337 0.572 555.1 104.3 1.01 SL 003c/09 100% 20.0% 0.351 0.564 557.7 108.4 1.05 SL 167c/08 100% 25.0% 0.352 0.562 557.9 109.8 1.05

(57) TABLE-US-00007 TABLE 7 A.sub.3B.sub.5O.sub.12:Ce (Lu, Y) garnets Fraction Lu, Fraction Ga, Lambda_dom/ rel. Sample number remainder Y remainder Al x y nm FWHM/nm QE SL 299c/08 100% 0.0% 0.393 0.557 564.2 112.5 1.00 SL 290c/08 88% 2.5% 0.396 0.556 564.6 113.2 1.02 SL 291c/08 68% 2.5% 0.414 0.550 567.1 115.4 1.01 SL 292c/08 78% 5.0% 0.400 0.555 565.2 113.7 1.01 SL 293c/08 78% 5.0% 0.400 0.556 565.1 114.3 1.01 SL 294c/08 78% 5.0% 0.401 0.555 565.3 114.8 1.02 SL 295c/08 78% 5.0% 0.401 0.555 565.3 113.8 1.02 SL 296c/08 88% 7.5% 0.388 0.559 563.5 112.8 1.02 SL 297c/08 68% 7.5% 0.402 0.555 565.4 114.4 1.03 SL 308c/08 88% 10.0% 0.383 0.560 562.8 112.1 1.03 SL 309c/08 83% 10.0% 0.387 0.559 563.3 112.5 1.03 SL 310c/08 83% 15.0% 0.381 0.560 562.5 113.0 1.03 SL 311c/08 78% 15.0% 0.385 0.559 563.1 112.3 1.02

(58) TABLE-US-00008 TABLE 4 The Eu concentration is 0.5% referred to M (in this Ca or Ca and Cu) Additive element Sample Molecular formula (x) Mol (add. elem.) rel. QE x y ? dom FWHM 176 CaALSiN.sub.3:Eu + 2 (0.5%) no 100.0% 0.664 0.332 610.7 87.3 180 CaAL.sub.1?xSi.sub.1+xN.sub.3?xO.sub.x:Eu + 2 (0.5%) O 0.020 103.9% 0.660 0.335 609.7 88.2 181 CaAL.sub.1?xSi.sub.1+xN.sub.3?xO.sub.x:Eu + 2 (0.5%) O 0.060 103.3% 0.658 0.338 608.8 88.4 182 CaAL.sub.1?xSi.sub.1+xN.sub.3?xO.sub.x:Eu + 2 (0.5%) 0 0.200 93.73% 0.634 0.358 603.2 90.2 183 CaAL.sub.1?xSi.sub.1+xN.sub.3?xO.sub.x:Eu + 2 (0.5%) O 0.600 77.7% 0.583 0.406 592.8 104.4 187 CaAL.sub.1+2xSi.sub.1?2xN.sub.3?xCl.sub.x:Eu + 2 (0.5%) Cl 0.005 100.4% 0.664 0.332 610.7 87.3 188 CaAL.sub.1+2xSi.sub.1?2xN.sub.3?xCl.sub.x:Eu + 2 (0.5%) Cl 0.020 100.5% 0.666 0.330 611.3 86.7 189 CaAL.sub.1+2xSi.sub.1?2xN.sub.3?xCl.sub.x:Eu + 2 (0.5%) Cl 0.030 101.4% 0.664 0.331 611.0 87.6 190 CaAL.sub.1+2xSi.sub.1?2xN.sub.3?xCl.sub.x:Eu + 2 (0.5%) Cl 0.050 101.2% 0.659 0.336 609.4 88.5 191 CaAL.sub.1+2xSi.sub.1?2xN.sub.3?xF.sub.x:Eu + 2 (0.5%) F 0.005 103.8% 0.670 0.327 612.4 87.0 192 CaAL.sub.1+2xSi.sub.1?2xN.sub.3?xF.sub.x:Eu + 2 (0.5%) F 0.010 101.4% 0.670 0.326 612.7 86.9 193 CaAL.sub.1+2xSi.sub.1?2xN.sub.3?xF.sub.x:Eu + 2 (0.5%) F 0.020 101.9% 0.668 0.327 612.4 87.2 194 CaAL.sub.1+2xSi.sub.1?2xN.sub.3?xF.sub.x:Eu + 2 (0.5%) F 0.050 99.5% 0.662 0.333 610.3 87.0 235 (Ca1 ? xCuxAL1 + 4xSi1 ? 4xN3 ? 2xF2x:Eu(0.5%) Cu, F 0.005 93.3% 0.665 0.332 610.7 86.4 (Ca.sub.1?xCu.sub.xAL.sub.1+4xSi.sub.1?4xN.sub.3?2xF.sub.2x:Eu(0.5%) 236 (Ca1 ? xCuxAL1 + 4xSi1 ? 4xN3 ? 2xF2x:Eu(0.5%) Cu, F 0.012 93.5% 0.661 0.335 609.7 87.4 (Ca.sub.1?xCu.sub.xAL.sub.1+4xSi.sub.1?4xN.sub.3?2xF.sub.2x:Eu(0.5%) 237 (Ca1 ? xCuxAL1 + 4xSi1 ? 4xN3 ? 2xF2x:Eu(0.5%) Cu, F 0.050 86.9% 0.640 0.354 604.2 91.5 (Ca.sub.1?xCu.sub.xAL.sub.1+4xSi.sub.1?4xN.sub.3?2xF.sub.2x:Eu(0.5%)