Title of Invention	"CARBIDONITRIDOSILICATE LUMINESCENT SUBSTANCE"
Abstract	The invention relates to a luminescent substance consisting of a doped host lattice which abcorbs as east one part of exciting radiation whet it is excited by a high-energy exciting rndiation, thereby releasing an enery poor emission radiation. According to said invention the host lattice is embodied in the form of a carbidonitridosilicate-basea conupound. An illuminant which is used for producing white light and comprises a light emitting element and said luminescent substance are also disclosed.

Title of Invention

"CARBIDONITRIDOSILICATE LUMINESCENT SUBSTANCE"

Abstract

The invention relates to a luminescent substance consisting of a doped host lattice which abcorbs as east one part of exciting radiation whet it is excited by a high-energy exciting rndiation, thereby releasing an enery poor emission radiation. According to said invention the host lattice is embodied in the form of a carbidonitridosilicate-basea conupound. An illuminant which is used for producing white light and comprises a light emitting element and said luminescent substance are also disclosed.

Full Text	CARBIDONITRIDOSILICATE LUMINESCENT SUBSTANCES The present invention relates to inorganic luminescent materials capable of effectively absorbing high-energy excitation radiation and converting it with a high efficiency into a lower-energy emission radiation. UV radiation or blue light in particular is suitable as the excitation radiation, resulting in emissions in the green, yellow, orange and/or red range of the visible spectrum following conversion of the radiation. It has long been known that inorganic luminescent substances may be used to advantage to visualize invisible radiation images (e.g., in radiological diagnostics or display technology) and also for the purpose of general illumination (e.g., in fluorescent lamps or to produce white LEDs). Such luminescent substances usually have a host lattice doped with special elements. So far mostly sulfides, halides and oxides have been used as the host lattice for such luminophores in industrial applications but also to a particularly great extent, complex salts of oxygen-containing acids (borates, aluminates, silicates, phosphates, molybdates, tungstates, etc.) are used. £P_ 1 5£0 274 Al -y3_jrei_atj2_d_ to improvem?- :•.ts of_nit_r_ide i'i:!£L • jxvri.i. 11' i.de conversion phosphors by surface coat i. n cj. Ocr.!p_oj..inds _of_ the _ccmposi ticns 1M-N:R .ano !'.,-_M-0-N : R, respectively, where L - Be, Mg, Ca, Si , Ba, Zn as "£~'_i_l -^ M :- C, 3i, Ge, 3n, Ti, Zr , Hf and K at: rare earth metal Only in recent years has it also been possible to develop nitridic materials (such as the red-emitting compounds of the type M2Si5N5::i;u2+ where M = Ca, Sr, Ba described by Hintzen et al. in EP I 104 799 Al and EP 1 238 041 Bl, for example) and oxynitridic materials (examples include the blue, green and yellow-emitting europium- or cerium-doped MSi202N2 compounds according to Delsing et al. in WO 2004/030109 Al; M = Ca, Sr, Ba) as the host lattice for synthesis of efficient luminescent substances. The interest in such luminophores has since then grown to a great extent, especially in conjunction with their advantageous use as conversion luminescent substances for the production of white LEDs. This is attributed in particular to the fact that because of the high covalency of the chemical bonds and the proven marked rigidity of the basic lattice, a particularly high chemical and thermal stability is expected of materials of this type. The disadvantages of the mostly sulfidic and oxygen-dominated conversion luminescent substances is mainly that their luminescence ft efficiency usually declines very rapidly at temperatures above 100°C. However, for the production of more advanced white LEDs with a higher wattage, conversion luminescent substances with a greatly improved thermal stability are needed. On the other hand, it should be pointed out in this context that all the inorganic conversion luminescent materials currently used industrially (yttrium aluminates, thiogallates, alkaline earth sulfides, alkaline earth silicates, nitrides, oxynitrides) which are used to produce white light in combination with blue-emitting LEDs, are without exception Eu2+ and/or Ce3+-activated systems with an extremely broadband emission. Electronic 5d-4f transitions which may easily be influenced by an external crystal field and thus naturally also by extinction centers that may be present are characteristic of such luminescent substances. The situation is fundamentally different than that when using luminophores in fluorescent lamps. In this case, the main substances used as red and green components are lineemitting luminescent substances in which the luminescence phenomena to be observed are attributed to transitions between the 4f electrons (4f-4f transitions) that are shielded with respect to the effects of external crystal fields. High covalent bonding components are also characteristic of another class of compounds only recently discovered. These are the carbidonitridosilicates containing rare earth metals and/or alkaline earth metals. The first representatives of this class of materials (e.g., the compounds Ho2Si4N6C, Tb2Si4NeC (cf. Hoppe et al., J. Mater. Chem 11 (2001) 3300) and (La,Y,Ca)2(Si, Al)4 (N, C), (cf. Lindel et al., J. Eur. Chem Soc. 25 (2005) 37) have been synthesized and described with respect to their basic physicochemical properties. Information about the luminescence of such compounds has so far been completely unavailable in the technical literature. Now, however, SCHMIDT et al. have presented cerium-activated carbidonitridosilicate materials, in particular luminescent substances having the composition Y2Si4NeC:Ce with an activator concentration of 5% Ce in the patent WO 2005/083037 Al, which was published after the priority date of the present application. On excitation with UV radiation or with the light of blue-emitting LEDs, these materials luminesce in a broadband in the yellow spectral range and, according to the published information, have practically the same performance data with regard to quantum yield, absorption efficiency and temperature characteristics as the corresponding parameters of other known yellow-emitting conversion luminescent substances such as yttrium aluminum garnets, which are also doped with cerium, or Eu2+-activated alkaline earth orthosilicates. However, the object of the present invention is to propose novel ^uminescent materials, in particular for use in efficient white LEDs, which are characterized by original or improved luminescence properties. This object is achieved by the luminescent substances defined in the attached Patent Claims 1 and 2. The inventive materials belong to the class of carbidonitrides, in particular carbidonitridosilicates. They may be used alone or in combination with other suitable luminophores as conversion luminescent substances for the production of light sources, in particular for the production of white-emitting LEDs. The insertion of carbon ions into the corresponding nitridosilicate matrix is associated with a further increase in the covalence of the lattice. Based on this fact, the lower tendency toward thermal extinction of the luminescence, the high chemical and thermal stability and the low tendency toward aging can be mentioned as special advantages of the inventive luminescent substances. A general formula for the luminescent substances according to the present invention would be: Ln(2-a-b+f)M (a+b-f )Si (4-c-d-e-f )M (c+d+e + f) N , 6-a+b-d+e) 0 (a + d) Cl-b-et where Ln denotes at least one of the metals indium (In), scandium (Sc), yttrium (Y) and for the rare earths, in jparticular for the elements lanthanum (La), gadolinium (Gd) and luthetium (Lu) and/or for mixtures of these metals. As shown in the general formula, however, in a special embodiment, Ln may also be replaced partially or entirely by a divalent metal M1, preferably by zinc (Zn) or by alkaline earth metals such as magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba) if equimolar amounts of nitrogen (N) are to be replaced by oxygen (0) or if carbon (C) is to be replaced by nitrogen (N). In yet another modification of this embodiment, silicon (Si) may be replaced by a component M11, e.g., by germanium (Ge) and/or boron (B) and/or aluminum (Al). In the last cases mentioned, equimolar amounts of N must also be replaced by 0 or equimolar amounts of C must be replaced by N or equimolar amounts of M1 must be replaced by Ln. Depending on the exact composition of the basic lattice of luminescent material, different crystal structures with different lattice sites for the incorporation of rare earth and/or transition metal activator ions can be implemented. Preferred activators include cerium and/or terbium and europium or certain transition metal elements that may be incorporated into the matrix as divalent ions (in particular Eu2+) or trivalent ions (in particular Ce3+, Tb3+, Eu3+) . The concentration of activators may be 0.001 to 1.5 mol activator per mol luminescent substance. The cerium which is optionally added as a coactivator may be present in concentrations of 0.0005 to 1.5 mol cerium per mol luminescent substance. Preferred embodiments of the inventive luminescent substances are determined by the following formulas: each with Ln = Y, La, Gd and/or Lu, where 0.001 and 0.001 The inventive luminescent substances emit a green, yellow, orange or red-colored luminescent radiation when excited in the UV spectral range (200 to 380 nm) and/or in the violet spectral range (380 to 420 nm) or in the blue spectral range (420 to 480 nm). They have an absorption for the excitation radiation and are also characterized by a high quantum efficiency and a low thermal luminescence extinction. Because of these features and additional advantageous properties, the inventive luminescent substances may be used advantageously both as individual components and as a mixture of several inventive luminescent substances or in combination (mixture) with other known blue, green, yellow or red-emitting conversion luminescent substances for the production of white LEDs. With the present invention, efficient rare-earth-activated luminescent substances with 4f-4f line spectra that can be excited in the blue spectral range are made available for the first time for the production of white LEDs, because it has surprisingly been found that simultaneous doping of certain inventive carbidonitridosilicate luminescent substance basic lattices with terbium and cerium ions leads to a green Tb3+ line emission that is excitable with the light of blue LEDs. Rare-earth-activated luminophores with 4f-4f line emissions have the advantages described above with respect to resistance to the effects of external crystal fields and extrinsic extinction factors. In addition, when using the inventive Ce3+--Tb3+-codoped carbidonitridosilicate luminescent substances as the green component in white LEDs, however, even more advantages can be utilized. First, the main peak of the Tb3+ emission, which is located at approx. 545 nm, has an extremely low half-value width in comparison with the corresponding broadband spectra; secondly, the emission spectrum consists of additional line groups which are distributed over the entire visible spectral range. The property mentioned first is advantageous when using corresponding white LEDs for background lighting of LCDs (adaptation of the emission characteristics to the color filters used), while the characteristic spectral distribution of the luminescence of the Ce3+-Tb3+-coactivated luminescent substances, which is variable within certain limits (by varying the Ce/Tb ratio) contributes toward achieving improved color reproduction values (CRI = color rendering index) in the case of use in white LEDs for general lighting. Another importan-; advantage of the inventive approach may be seen in the fact that a novel red-emitting conversion luminescent substance can be synthesized in this way. Much stronger crystal fields can be implemented in inorganic nitride compounds than in the case of the oxygen-dominated luminescent substances. This is an important prerequisite for the desired :red shift of the luminescence emitted by Eu2+ ions, for example. The experiments conducted in conjunction with the present invention have now surprisingly shown that even in doping the inventive basic lattice with europium ions, redemitting luminescent substances are formed with excitation spectra that are suitable for use in white LEDs. Additional details, advantages and embodiments of the present invention are derived from the description of the manufacturing conditions for the luminophores as well as the accompanying figures, in which: Fig. 1 shows the excitation spectra (left part of the figure) and emission spectra (right part) of cerium-doped Y2Si4N6C luminescent substances, Fig. 2 shows the diffuse reflection spectrum, the excitation spectrum and the line emission spectrum of a Tb3+-activated Y2Si4N6C phosphorus, Fig. 3 shows the excitation spectrum (left part of the figure) and the emission spectrum (right part) of a Ce- and Tb-codoped Y2Si4NeC material, and Fig. 4 shows the excitation and emission spectrum of a europium-activated Y2Si4NeC luminescent material. The carbidonitridosilicates containing the rare earth metals and/or alkaline earth metals as defined in the general formula given above are preferably produced by a high-temperature solid-state reaction. The details of the synthesis are described below as an example on the basis of a general preparation procedure and two exemplary embodiments for Ce- and Tb-doped and/or Eu-doped carbidonitridosilicate luminescent substances. As starting materials, "-SllNi- l'-Si,.N\|, carbon powder, SiC and the rare earths yttrium, cerium, terbium and europium are each used in metallic form. Before performing additional process steps, the rare earth metals are first nitrated in a nitrogen or ammonia atmosphere. Then the nitrated compounds are weighed in the respective stoichiometric amounts together with SiaN,), SiC or carbon powder and mixed thoroughly. Because of the moisture sensitivity of some starting materials, all these manipulations are performed in a glovebox under dry nitrogen. The powder mixtures are placed in suitable crucibles and calcined for 2 to 48 hours at temperatures of 1500°C to 1800°C in high-temperature ovens under pure nitrogen. After the end of the calcining process, the samples are cooled to room temperature and optionally subjected to a suitable af te:rtreatment. Example 1 For preparation of the terbium- and cerium-activated carbidonitridosilicates Y1.0oSi4N6C : Tbo.ggCeo.ou terbium metal is first nitrated for 12 hours at 1200°C in a horizontal tubular oven under a pure nitrogen atmosphere to yield TbNx (>• -0.99). The starting materials 34.24 g TbNx, 17.78 g yttrium metal, 0.28 g cerium me~al, '"•-"' '3 « 3 s M and 8_Q 2 g sic are then mixed thoroughly in an agate mortar under a dry nitrogen atmosphere and then placed in a molybdenum crucible. This powder mixture is then calcined for 10 hours at 1600°C under pure nitrogen and next cooled to room temperature in the oven. After removing soluble components and those that have not reacted,, there remains a green-emitting luminescent substance having the composition Example 2 To produce a carbidonitridosilicate activated with 5% europium and having the composition Gdi.8Sro.2Si4N6.2Co.8» pure strontium metal and europium metal are nitrated to the precursors Sr3N2 and EuN at 850°C for two hours under a pure nitrogen atmosphere in a horizontal tubular oven. Then 56.61 g gadolinium metal, 2.91 g Sr3N2, 1.66 g EuN, 29.93 g «-.'•:i-H. and 6 .42 g SiC are mixed thoroughly in a dried nitrogen atmosphere and placed in a thermally resistant crucible. The mixture is calcined for 24 hours at 1750°C in a nitrogen-hydrogen atmosphere (90:10). After suitable sample workout, a substance with an efficient red luminescence is obtained. The accompanying figures are mostly self-explanatory for those skilled in the art of luminescent substances. The basic information has already been presented above. As supplementary information, only a few particulars are given below. Fig. 1 shows that Y2Si4N6C luminescent substances doped only with cerium ions will luminesce in the yellow-green spectral range when excited with radiation between 360 and 450 nm. The various curves are each based on different doping concentrations whose values are shown in the diagram. Fig. 2 shows that Y2Si4N6C luminescent substances activated with Tb3+ alone must be excited in the range between 280 and 320 nm to achieve an efficient green Tb3+ line emission. Fig. 3 shows well that a Ce- and Tb-codoped Y2Si4N6C host lattice can also be excited efficiently in the range between 360 and 450 nm. In the selected example, this results in a Tb3+ line emission superimposed on the Ce3* broadband emission. However, Ce/Tb concentration ratios at which the terbium line emission is definitely predominant and the cerium luminescence is greatly suppressed can also be found. Finally, Fig. 4 shows that even the emission band of the europium-activated Y2Si4N6C matrix recorded at a maximum wavelength of 613 nm can be excited in the range of 350 to 480 nm that is of interest. Although only a few embodiments have been described here in greater detail, it will be clear to those skilled in the art that numerous modifications of the inventive luminescent substance are possible. The possible variations have been indicated by providing equations of general validity and listing possible replacement elements. Patent Claims: 1. Luminescent substance comprising a doped host lattice, which, on excitation with a high-energy excitation radiation, absorbs at least a port ion of this excitation radiation and then emits a lower-energy emission radiation, characterized in that the host lattice is a carbidonitridosilicate compound, which is not doped with cerium as an activator. 2. Luminescent substance from a doped host lattice, which absorbs at least a portion of the excitation radiation on excitation with a high-energy excitation radiation and then emits a lower-energy emission radiation, characterized in that the host lattice is a compound having the following general formula (Formula Removed) where • indium (In), • scandium (Sc), • yttrium (Y), • rare earths; M1 is a divalent metal or a mixture of divalent metals; and M11 is an element or a mixture of elements of the following group: • germanium (Ge), • boron (B), • aluminum (Al). 3. Luminescent substance according to Claim 2, characterized in that when M: and/or M11 are present, equimolar amounts of nitrogen (N) are replaced by oxygen (0) and/or equimolar amounts of carbon (C) are replaced by nitrogen (N). 4. Luminescent substance according to Claim 2 or 3, characterized in that the doped activators in the host lattice are divalent or trivalent rare earth ions or transition metal ions. 5. Luminescent substance according to Claim 4, characterized in that the activators are Eu2+, Ce3+, Tb3+ and/or Eu3+ ions. 6. Luminescent substance according to Claim 5, characterized in that Tb3+ ions as activators and Ce3+ ions as coactivators are doped into the host lattice. 7. Luminescent substance according to any one of Claims 4 through 6, characterized in that the concentration of activators is 0.001 to 1.5 mol activator per mol luminescent substance. 8. Luminescent substance according to any one of Claims 4 through 7, characterized in that cerium as the coactivator is doped into the hcst lattice in a concentration of 0.0005 to 1.5 mol cerium per mol luminescent substance. 9. Luminescent substance according to any one of Claims 2 through 8, characterized in that at least one of the parameters c, d, e or f is selected to be greater than zero. 10. Luminescent substance according to any one of Claims 2 through 9, characterized in that the component Ln is an element from the group lanthanum (La), gadolinium (Gd) and luthetium (Lu) . 11. Luminescent substance according to any one of Claims 2 through 10, characterized in that the component M1 contains zinc (Zn). 12. Luminescent substance according to any one of Claims 2 through 11, characterized in that the component M1 contains one or more alkaline earth metals, in particular Mg, Ca, Sr, Ba. 13. Luminescent substance according to any one of Claims 2 through 12, characterized in that at least one of parameters a or d is selected to be greater than zero. 14. Luminescent substance according to any one of Claims 1 through 4, characterized in that it is defined by one of the following formulas: where Ln = Y, La, Gd and/or Lu and where 0.001 15. Luminescent substance according to any one of Claims 1 through 14, characterized in that it can be excited to emission by radiation with wavelengths of 200 to 480 nm. 16. Luminescent substance according to Claim 15, characterized in that with appropriate excitation a green, yellow, orange or red-colored emission radiation is emitted. 17. Luminescent substance according to any one of Claims 1 through 16, characterized in that on excitation with blue excitation radiation, it emits a radiation having a line spectrum which results from 4f-4f electron transitions. 18. Luminescent means for generating white light, characterized in that it comprises a light-emitting element and at least one luminescent substance according to any one of Claims 1 through 17, which is excited by the excitation radiation generated by the emitted element and emits emission radiation in another spectral range. 19. Luminescent means according to Claim 18, characterized in that the light-emitting element is an LED. 20. Luminescent means according to Claim 18 or 19, characterized in that the LED emits light in the wavelength range of 200 to 480 nm and the luminescent substance emits blue, green, yellow or red radiation.

Full Text

CARBIDONITRIDOSILICATE LUMINESCENT SUBSTANCES
The present invention relates to inorganic luminescent
materials capable of effectively absorbing high-energy
excitation radiation and converting it with a high
efficiency into a lower-energy emission radiation. UV
radiation or blue light in particular is suitable as the
excitation radiation, resulting in emissions in the green,
yellow, orange and/or red range of the visible spectrum
following conversion of the radiation.
It has long been known that inorganic luminescent
substances may be used to advantage to visualize invisible
radiation images (e.g., in radiological diagnostics or
display technology) and also for the purpose of general
illumination (e.g., in fluorescent lamps or to produce
white LEDs). Such luminescent substances usually have a
host lattice doped with special elements. So far mostly
sulfides, halides and oxides have been used as the host
lattice for such luminophores in industrial applications
but also to a particularly great extent, complex salts of
oxygen-containing acids (borates, aluminates, silicates,
phosphates, molybdates, tungstates, etc.) are used.
£P_ 1 5£0 274 Al -y3_jrei_atj2_d_ to improvem?- :•.ts of_nit_r_ide i'i:!£L
• jxvri.i. 11' i.de conversion phosphors by surface coat i. n cj.
Ocr.!p_oj..inds _of_ the _ccmposi ticns 1M-N:R .ano !'.,-_M-0-N : R,
respectively, where L - Be, Mg, Ca, Si , Ba, Zn as "£~'_i_l -^
M :- C, 3i, Ge, 3n, Ti, Zr , Hf and K at: rare earth metal
Only in recent years has it also been possible to develop
nitridic materials (such as the red-emitting compounds of
the type M2Si5N5::i;u2+ where M = Ca, Sr, Ba described by
Hintzen et al. in EP I 104 799 Al and EP 1 238 041 Bl, for
example) and oxynitridic materials (examples include the
blue, green and yellow-emitting europium- or cerium-doped
MSi202N2 compounds according to Delsing et al. in
WO 2004/030109 Al; M = Ca, Sr, Ba) as the host lattice for
synthesis of efficient luminescent substances. The interest
in such luminophores has since then grown to a great
extent, especially in conjunction with their advantageous
use as conversion luminescent substances for the production
of white LEDs. This is attributed in particular to the fact
that because of the high covalency of the chemical bonds
and the proven marked rigidity of the basic lattice, a
particularly high chemical and thermal stability is
expected of materials of this type. The disadvantages of
the mostly sulfidic and oxygen-dominated conversion
luminescent substances is mainly that their luminescence
ft
efficiency usually declines very rapidly at temperatures
above 100°C. However, for the production of more advanced
white LEDs with a higher wattage, conversion luminescent
substances with a greatly improved thermal stability are
needed.
On the other hand, it should be pointed out in this context
that all the inorganic conversion luminescent materials
currently used industrially (yttrium aluminates,
thiogallates, alkaline earth sulfides, alkaline earth
silicates, nitrides, oxynitrides) which are used to produce
white light in combination with blue-emitting LEDs, are
without exception Eu2+ and/or Ce3+-activated systems with an
extremely broadband emission. Electronic 5d-4f transitions
which may easily be influenced by an external crystal field
and thus naturally also by extinction centers that may be
present are characteristic of such luminescent substances.
The situation is fundamentally different than that when
using luminophores in fluorescent lamps. In this case, the
main substances used as red and green components are lineemitting
luminescent substances in which the luminescence
phenomena to be observed are attributed to transitions
between the 4f electrons (4f-4f transitions) that are
shielded with respect to the effects of external crystal
fields.
High covalent bonding components are also characteristic of
another class of compounds only recently discovered. These
are the carbidonitridosilicates containing rare earth
metals and/or alkaline earth metals. The first
representatives of this class of materials (e.g., the
compounds Ho2Si4N6C, Tb2Si4NeC (cf. Hoppe et al., J. Mater.
Chem 11 (2001) 3300) and (La,Y,Ca)2(Si, Al)4 (N, C), (cf. Lindel
et al., J. Eur. Chem Soc. 25 (2005) 37) have been
synthesized and described with respect to their basic
physicochemical properties.
Information about the luminescence of such compounds has so
far been completely unavailable in the technical
literature. Now, however, SCHMIDT et al. have presented
cerium-activated carbidonitridosilicate materials, in
particular luminescent substances having the composition
Y2Si4NeC:Ce with an activator concentration of 5% Ce in the
patent WO 2005/083037 Al, which was published after the
priority date of the present application. On excitation
with UV radiation or with the light of blue-emitting LEDs,
these materials luminesce in a broadband in the yellow
spectral range and, according to the published information,
have practically the same performance data with regard to
quantum yield, absorption efficiency and temperature
characteristics as the corresponding parameters of other
known yellow-emitting conversion luminescent substances
such as yttrium aluminum garnets, which are also doped with
cerium, or Eu2+-activated alkaline earth orthosilicates.
However, the object of the present invention is to propose
novel ^uminescent materials, in particular for use in
efficient white LEDs, which are characterized by original
or improved luminescence properties.
This object is achieved by the luminescent substances
defined in the attached Patent Claims 1 and 2.
The inventive materials belong to the class of
carbidonitrides, in particular carbidonitridosilicates.
They may be used alone or in combination with other
suitable luminophores as conversion luminescent substances
for the production of light sources, in particular for the
production of white-emitting LEDs.
The insertion of carbon ions into the corresponding
nitridosilicate matrix is associated with a further
increase in the covalence of the lattice. Based on this
fact, the lower tendency toward thermal extinction of the
luminescence, the high chemical and thermal stability and
the low tendency toward aging can be mentioned as special
advantages of the inventive luminescent substances.
A general formula for the luminescent substances according
to the present invention would be:
Ln(2-a-b+f)M (a+b-f )Si (4-c-d-e-f )M (c+d+e + f) N , 6-a+b-d+e) 0 (a + d) Cl-b-et
where Ln denotes at least one of the metals indium
(In), scandium (Sc), yttrium (Y) and for the rare
earths, in jparticular for the elements lanthanum (La),
gadolinium (Gd) and luthetium (Lu) and/or for mixtures
of these metals.
As shown in the general formula, however, in a special
embodiment, Ln may also be replaced partially or entirely
by a divalent metal M1, preferably by zinc (Zn) or by
alkaline earth metals such as magnesium (Mg), calcium (Ca),
strontium (Sr) and barium (Ba) if equimolar amounts of
nitrogen (N) are to be replaced by oxygen (0) or if carbon
(C) is to be replaced by nitrogen (N).
In yet another modification of this embodiment, silicon
(Si) may be replaced by a component M11, e.g., by germanium
(Ge) and/or boron (B) and/or aluminum (Al). In the last
cases mentioned, equimolar amounts of N must also be
replaced by 0 or equimolar amounts of C must be replaced by
N or equimolar amounts of M1 must be replaced by Ln.
Depending on the exact composition of the basic lattice of
luminescent material, different crystal structures with
different lattice sites for the incorporation of rare earth
and/or transition metal activator ions can be implemented.
Preferred activators include cerium and/or terbium and
europium or certain transition metal elements that may be
incorporated into the matrix as divalent ions (in
particular Eu2+) or trivalent ions (in particular Ce3+, Tb3+,
Eu3+) .
The concentration of activators may be 0.001 to 1.5 mol
activator per mol luminescent substance. The cerium which
is optionally added as a coactivator may be present in
concentrations of 0.0005 to 1.5 mol cerium per mol
luminescent substance.
Preferred embodiments of the inventive luminescent
substances are determined by the following formulas:
each with Ln = Y, La, Gd and/or Lu, where 0.001 and 0.001 The inventive luminescent substances emit a green, yellow,
orange or red-colored luminescent radiation when excited in
the UV spectral range (200 to 380 nm) and/or in the violet
spectral range (380 to 420 nm) or in the blue spectral
range (420 to 480 nm). They have an absorption for the
excitation radiation and are also characterized by a high
quantum efficiency and a low thermal luminescence
extinction.
Because of these features and additional advantageous
properties, the inventive luminescent substances may be
used advantageously both as individual components and as a
mixture of several inventive luminescent substances or in
combination (mixture) with other known blue, green, yellow
or red-emitting conversion luminescent substances for the
production of white LEDs.
With the present invention, efficient rare-earth-activated
luminescent substances with 4f-4f line spectra that can be
excited in the blue spectral range are made available for
the first time for the production of white LEDs, because it
has surprisingly been found that simultaneous doping of
certain inventive carbidonitridosilicate luminescent
substance basic lattices with terbium and cerium ions leads
to a green Tb3+ line emission that is excitable with the
light of blue LEDs. Rare-earth-activated luminophores with
4f-4f line emissions have the advantages described above
with respect to resistance to the effects of external
crystal fields and extrinsic extinction factors. In
addition, when using the inventive Ce3+--Tb3+-codoped
carbidonitridosilicate luminescent substances as the green
component in white LEDs, however, even more advantages can
be utilized. First, the main peak of the Tb3+ emission,
which is located at approx. 545 nm, has an extremely low
half-value width in comparison with the corresponding
broadband spectra; secondly, the emission spectrum consists
of additional line groups which are distributed over the
entire visible spectral range. The property mentioned first
is advantageous when using corresponding white LEDs for
background lighting of LCDs (adaptation of the emission
characteristics to the color filters used), while the
characteristic spectral distribution of the luminescence of
the Ce3+-Tb3+-coactivated luminescent substances, which is
variable within certain limits (by varying the Ce/Tb ratio)
contributes toward achieving improved color reproduction
values (CRI = color rendering index) in the case of use in
white LEDs for general lighting.
Another importan-; advantage of the inventive approach may
be seen in the fact that a novel red-emitting conversion
luminescent substance can be synthesized in this way. Much
stronger crystal fields can be implemented in inorganic
nitride compounds than in the case of the oxygen-dominated
luminescent substances. This is an important prerequisite
for the desired :red shift of the luminescence emitted by
Eu2+ ions, for example.
The experiments conducted in conjunction with the present
invention have now surprisingly shown that even in doping
the inventive basic lattice with europium ions, redemitting
luminescent substances are formed with excitation
spectra that are suitable for use in white LEDs.
Additional details, advantages and embodiments of the
present invention are derived from the description of the
manufacturing conditions for the luminophores as well as
the accompanying figures, in which:
Fig. 1 shows the excitation spectra (left part of the
figure) and emission spectra (right part) of
cerium-doped Y2Si4N6C luminescent substances,
Fig. 2 shows the diffuse reflection spectrum, the
excitation spectrum and the line emission
spectrum of a Tb3+-activated Y2Si4N6C phosphorus,
Fig. 3 shows the excitation spectrum (left part of the
figure) and the emission spectrum (right part) of
a Ce- and Tb-codoped Y2Si4NeC material, and
Fig. 4 shows the excitation and emission spectrum of a
europium-activated Y2Si4NeC luminescent material.
The carbidonitridosilicates containing the rare earth
metals and/or alkaline earth metals as defined in the
general formula given above are preferably produced by a
high-temperature solid-state reaction. The details of the
synthesis are described below as an example on the basis of
a general preparation procedure and two exemplary
embodiments for Ce- and Tb-doped and/or Eu-doped
carbidonitridosilicate luminescent substances.
As starting materials, "-SllNi- l'-Si,.N|, carbon powder, SiC and
the rare earths yttrium, cerium, terbium and europium are
each used in metallic form. Before performing additional
process steps, the rare earth metals are first nitrated in
a nitrogen or ammonia atmosphere. Then the nitrated
compounds are weighed in the respective stoichiometric
amounts together with SiaN,), SiC or carbon powder and mixed
thoroughly. Because of the moisture sensitivity of some
starting materials, all these manipulations are performed
in a glovebox under dry nitrogen. The powder mixtures are
placed in suitable crucibles and calcined for 2 to 48 hours
at temperatures of 1500°C to 1800°C in high-temperature
ovens under pure nitrogen. After the end of the calcining
process, the samples are cooled to room temperature and
optionally subjected to a suitable af te:rtreatment.
Example 1
For preparation of the terbium- and cerium-activated
carbidonitridosilicates Y1.0oSi4N6C : Tbo.ggCeo.ou terbium metal
is first nitrated for 12 hours at 1200°C in a horizontal
tubular oven under a pure nitrogen atmosphere to yield TbNx
(>• -0.99).
The starting materials 34.24 g TbNx, 17.78 g yttrium metal,
0.28 g cerium me~al, '"•-"' '3 « 3 s M and 8_Q 2 g sic are then
mixed thoroughly in an agate mortar under a dry nitrogen
atmosphere and then placed in a molybdenum crucible. This
powder mixture is then calcined for 10 hours at 1600°C
under pure nitrogen and next cooled to room temperature in
the oven. After removing soluble components and those that
have not reacted,, there remains a green-emitting
luminescent substance having the composition
Example 2
To produce a carbidonitridosilicate activated with 5%
europium and having the composition Gdi.8Sro.2Si4N6.2Co.8» pure
strontium metal and europium metal are nitrated to the
precursors Sr3N2 and EuN at 850°C for two hours under a pure
nitrogen atmosphere in a horizontal tubular oven. Then
56.61 g gadolinium metal, 2.91 g Sr3N2, 1.66 g EuN, 29.93 g
«-.'•:i-H. and 6 .42 g SiC are mixed thoroughly in a dried
nitrogen atmosphere and placed in a thermally resistant
crucible. The mixture is calcined for 24 hours at 1750°C in
a nitrogen-hydrogen atmosphere (90:10). After suitable
sample workout, a substance with an efficient red
luminescence is obtained.
The accompanying figures are mostly self-explanatory for
those skilled in the art of luminescent substances. The
basic information has already been presented above. As
supplementary information, only a few particulars are given
below.
Fig. 1 shows that Y2Si4N6C luminescent substances doped only
with cerium ions will luminesce in the yellow-green
spectral range when excited with radiation between 360 and
450 nm. The various curves are each based on different
doping concentrations whose values are shown in the
diagram.
Fig. 2 shows that Y2Si4N6C luminescent substances activated
with Tb3+ alone must be excited in the range between 280 and
320 nm to achieve an efficient green Tb3+ line emission.
Fig. 3 shows well that a Ce- and Tb-codoped Y2Si4N6C host
lattice can also be excited efficiently in the range
between 360 and 450 nm. In the selected example, this
results in a Tb3+ line emission superimposed on the Ce3*
broadband emission. However, Ce/Tb concentration ratios at
which the terbium line emission is definitely predominant
and the cerium luminescence is greatly suppressed can also
be found.
Finally, Fig. 4 shows that even the emission band of the
europium-activated Y2Si4N6C matrix recorded at a maximum
wavelength of 613 nm can be excited in the range of 350 to
480 nm that is of interest.
Although only a few embodiments have been described here in
greater detail, it will be clear to those skilled in the
art that numerous modifications of the inventive
luminescent substance are possible. The possible variations
have been indicated by providing equations of general
validity and listing possible replacement elements.

Patent Claims:
1. Luminescent substance comprising a doped host lattice,
which, on excitation with a high-energy excitation
radiation, absorbs at least a port ion of this
excitation radiation and then emits a lower-energy
emission radiation, characterized in that the host
lattice is a carbidonitridosilicate compound, which is
not doped with cerium as an activator.
2. Luminescent substance from a doped host lattice, which
absorbs at least a portion of the excitation radiation
on excitation with a high-energy excitation radiation
and then emits a lower-energy emission radiation,
characterized in that the host lattice is a compound
having the following general formula
(Formula Removed)
where
• indium (In),
• scandium (Sc),
• yttrium (Y),
• rare earths;
M1 is a divalent metal or a mixture of divalent metals; and
M11 is an element or a mixture of elements of the following group:
• germanium (Ge),
• boron (B),
• aluminum (Al).
3. Luminescent substance according to Claim 2,
characterized in that when M: and/or M11 are present,
equimolar amounts of nitrogen (N) are replaced by
oxygen (0) and/or equimolar amounts of carbon (C)
are replaced by nitrogen (N).
4. Luminescent substance according to Claim 2 or 3,
characterized in that the doped activators in the
host lattice are divalent or trivalent rare earth
ions or transition metal ions.
5. Luminescent substance according to Claim 4,
characterized in that the activators are Eu2+, Ce3+,
Tb3+ and/or Eu3+ ions.
6. Luminescent substance according to Claim 5,
characterized in that Tb3+ ions as activators and Ce3+
ions as coactivators are doped into the host
lattice.
7. Luminescent substance according to any one of Claims
4 through 6, characterized in that the concentration
of activators is 0.001 to 1.5 mol activator per mol
luminescent substance.
8. Luminescent substance according to any one of Claims
4 through 7, characterized in that cerium as the
coactivator is doped into the hcst lattice in a
concentration of 0.0005 to 1.5 mol cerium per mol
luminescent substance.
9. Luminescent substance according to any one of Claims
2 through 8, characterized in that at least one of
the parameters c, d, e or f is selected to be
greater than zero.
10. Luminescent substance according to any one of Claims
2 through 9, characterized in that the component Ln
is an element from the group lanthanum (La),
gadolinium (Gd) and luthetium (Lu) .
11. Luminescent substance according to any one of Claims
2 through 10, characterized in that the component M1
contains zinc (Zn).
12. Luminescent substance according to any one of Claims
2 through 11, characterized in that the component M1
contains one or more alkaline earth metals, in
particular Mg, Ca, Sr, Ba.
13. Luminescent substance according to any one of Claims
2 through 12, characterized in that at least one of
parameters a or d is selected to be greater than
zero.
14. Luminescent substance according to any one of Claims
1 through 4, characterized in that it is defined by
one of the following formulas:
where Ln = Y, La, Gd and/or Lu and where 0.001 15. Luminescent substance according to any one of Claims 1
through 14, characterized in that it can be excited to
emission by radiation with wavelengths of 200 to
480 nm.
16. Luminescent substance according to Claim 15,
characterized in that with appropriate excitation a
green, yellow, orange or red-colored emission
radiation is emitted.
17. Luminescent substance according to any one of Claims 1
through 16, characterized in that on excitation with
blue excitation radiation, it emits a radiation having
a line spectrum which results from 4f-4f electron
transitions.
18. Luminescent means for generating white light,
characterized in that it comprises a light-emitting
element and at least one luminescent substance
according to any one of Claims 1 through 17, which is
excited by the excitation radiation generated by the
emitted element and emits emission radiation in
another spectral range.
19. Luminescent means according to Claim 18, characterized
in that the light-emitting element is an LED.
20. Luminescent means according to Claim 18 or 19,
characterized in that the LED emits light in the
wavelength range of 200 to 480 nm and the luminescent
substance emits blue, green, yellow or red radiation.

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Patent Number

267004

Indian Patent Application Number

1848/DELNP/2008

PG Journal Number

26/2015

Publication Date

26-Jun-2015

Grant Date

22-Jun-2015

Date of Filing

29-Feb-2008

Name of Patentee

LEUCHTSTOFFWERK BREITUNGEN GMBH,

Applicant Address

LANGE SOMME 17, 98597 BREITUNGEN, GERMANY.

Inventors:

#	Inventor's Name	Inventor's Address
1	STARICK DETLEF,	STEINSTRASSE 40, 17489 GREIFSWALD GERMANY.
2	ROSLER SVEN,	SCHEIDLERSTRASSE 26, 99817 EISENACH GERMANY.
3	LI YUAN QIANG,	305-0032, 3-21 TAKEZONO, 510 BUILDING 409, TSUKUBA, IBARAKI, IBARAKI 305 JAPAN.
4	ROSLER SYLKE,	SCHEIDLERSTRASSE 26, 99817 EISENACH GERMANY.
5	HINTZEN HUBERTUS THERESIA	KANUNNIKENSVEN 24, NL-5646 JE EINDHOVEN THE NETHERLANDS.

PCT International Classification Number

H05B 33/14

PCT International Application Number

PCT/EP2006/065788

PCT International Filing date

2006-08-29

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2005 041 153.3	2005-08-30	Germany