Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/0883—Arsenides; Nitrides; Phosphides
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
  • C09K11/77067—Silicon Nitrides or Silicon Oxynitrides
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
  • H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source

Definitions

• the present invention generally relates to an illumination system comprising a radiation source and a fluorescent material comprising a phosphor.
• the invention also relates to a phosphor for use in such illumination system.
• the invention relates to an illumination system and fluorescent material comprising a phosphor for the generation of specific, colored light, including white light, by luminescent down conversion and additive color mixing based an a ultraviolet or blue radiation emitting radiation source.
• a light- emitting diode as a radiation source is especially contemplated.
• Previous white light illumination systems have been based in particular either on the trichromatic (RGB) approach, i.e. on mixing three colors, namely red, green and blue, in which case the components of the output light may be provided by a phosphor and/or by the primary emission of the LED or in a second, simplified solution, on the dichromatic (B Y) approach, mixing yellow and blue colors, in which case the yellow secondary component of the output light may be provided by a yellow phosphor and the blue component may be provided by a phosphor or by the primary emission of a blue LED.
• RGB trichromatic
• B Y dichromatic
• the dichromatic approach as disclosed e.g. U.S. Patent 5,998,925 uses a blue light emitting diode of InGaN based semiconductor material combined with an Y 3 Al 5 O 12 :Ce (YAG-Ce 3+ ) phosphor.
• the YAG-Ce 3+ phosphor is coated on the InGaN LED, and a portion of the blue light emitted from the LED is converted to yellow light by the phosphor. Another portion of the blue light from the LED is transmitted through the phosphor.
• this system emits both blue light, emitted from the LED, and yellow light emitted from the phosphor.
• the mixture of blue and yellow emission bands are perceived as white light by an observer with a typical CRI in the middle 70ties and a color temperature Tc, that ranges from about 6000 K to about 8000 K.
• Tc color temperature
• a concern with the LED according to US 5,998,925 is that the "white" output light has an undesirable color balance for true color rendition.
• the figure of merit is the color-rendering index (CRI).
• CRI color-rendering index
• Measuring the color-rendering index is a relative measurement of how the color rendition of an illumination system compares to that of a black body radiator.
• the CRI equals 100 if the color coordinates of a set of test colors being illuminated by the illumination system are the same as the coordinates of the same test colors being irradiated by a black body radiator.
• True color rendition is of importance as colors in general have the role of providing various information of the visual environment for humans. Colors have a particularly great role for the visual information received by car drivers of cars driving on roads or in tunnels. For example, on roads and in tunnels, which are illuminated by lamps of low CRI, it is difficult to distinguish white and yellow lane marking on the road surface.
• red is coded for important meanings such as danger, prohibition, stop and fire fighting. Therefore important point in improving the visual environment from the viewpoint of safety is an illumination that enhances red surfaces.
• Desirable characteristics for illumination systems for general purposes are also high brightness at economical cost.
• the present invention provides an illumination system, comprising a radiation source and a fluorescent material comprising at least one phosphor capable of absorbing a part of light emitted by the radiation source and emitting light of wavelength different from that of the absorbed light; wherein said at least one phosphor is a ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e : Yb z , wherein O ⁇ x ⁇ l; O ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2; 0 ⁇ a ⁇ 2;0 ⁇ b ⁇ 2;0 ⁇ c ⁇ 2;0 ⁇ d ⁇ 7;0 ⁇ e ⁇ 2.
• An illumination system can provide a composite white output light that is well balanced with respect to color.
• the composite white output light has a greater amount of emission in the red color range than the conventional illumination system. This characteristic makes the device ideal for applications in which a true color rendition is required.
• Such applications of the invention include inter alias traffic lighting, street lighting, security lighting and lighting of automated factory, and signal lighting for cars and traffic.
• a radiation source is a light emitting diode.
• a white light illumination system comprising a blue-light emitting diode having a peak emission wavelength in the range of 420 to 480 nm as a radiation source and a fluorescent material comprising at least one phosphor, that is a ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein 0 ⁇ x ⁇ 1; O ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2; 0 ⁇ a ⁇ 2; 0 ⁇ b ⁇ 2; 0 ⁇ c ⁇ 2; 0 ⁇ d ⁇ 7; 0 ⁇ e ⁇ 2.
• Such illumination system will provide white light in operation.
• the blue light emitted by the LED excites the phosphor, causing it to emit yellow light.
• the blue light emitted by the LED is transmitted through the phosphor and is mixed with the yellow light emitted by the phosphor.
• the viewer perceives the mixture of blue and yellow light as white light.
• An essential factor is that the yellow to red phosphors of the ytterbium(II)- activated oxonitridosilicate type are so broad-banded that they also have a sufficient proportion of the emission throughout the whole spectral region.
• the invention provides a white light illumination system comprising a blue-light emitting diode having a peak emission wavelength in the range of 460 to 480 nm as a radiation source and a fluorescent material comprising a ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein 0 ⁇ x ⁇ l;0 ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2;
• the color rendition of the white light illumination system according to the invention may be further improved.
• the fluorescent material of this embodiment may be a phosphor blend, comprising a ytterbium(II)-activated oxonitridosilicate of general formula (Sri -x-y-z Ca x Ba y ) a Si b Al c N d O e : Yb z , wherein O ⁇ x ⁇ l; O ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2;
• Such red phosphor may be selected from the group of Eu(II)-activated phosphors, selected from the group (Ca 1-x Sr x ) S:Eu, wherein O ⁇ x ⁇ l and (Sr 1-x-y Ba x Ca y ) 2-z Si 5- a Al a N 8-a O a :Eu z wherein 0 ⁇ a ⁇ 5, 0 ⁇ x ⁇ l, O ⁇ y ⁇ l and 0 ⁇ z ⁇ l.
• the fluorescent material may be a phosphor blend, comprising ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x-y- z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein
• Such yellow-to-green phosphor may be selected from the group comprising (Baj_ ⁇ Sr x )2 Si ⁇ 4: Eu, wherein O ⁇ x ⁇ l, SrGa2S4
• the emission spectrum of such a fluorescent material comprising additional phosphors has the appropriate wavelengths to obtain together with the blue light of the LED and the yellow to red light of the ytterbium(II)-activated oxonitridosilicate type phosphor according to the invention a high quality white light with good color rendering at the required color temperature.
• a white light illumination system wherein the radiation source is selected from the light emitting diodes having an emission with a peak emission wavelength in the UV-range of 200 to 420 nm and the fluorescent material comprises at least one phosphor, that is a ytterbium(II)-activated oxonitridosilicate of general formula
• the fluorescent material according to this embodiment may comprise a white light emitting phosphor blend, comprising a ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein
• Such blue phosphor may be selected from the group comprising BaMgAl 10 0 17: Eu, Ba 5 SiO 4 (Cl 5 Br) 6 : Eu, CaLn 2 S 4: Ce, wherein Ln comprises lanthanum and all lanthanide metals and (Sr 5 Ba 5 Ca) 5 (PO 4 ) 3 Cl:Eu.
• a second aspect of the present invention provides an illumination system emitting red to yellow light.
• Applications of the invention include security lighting as well as signal lighting for cars and traffic.
• the radiation source is selected from the blue light emitting diodes having an emission with a peak emission wavelength in the range of 400 to 490 nm and the fluorescent material comprises at least one phosphor, that is a ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein 0 ⁇ x ⁇ 1; O ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2; 0 ⁇ a ⁇ 2; 0 ⁇ b ⁇ 2;0 ⁇ c ⁇ 2;0 ⁇ d ⁇ 7;0 ⁇ e ⁇ 2.
• the radiation source is selected from the blue light emitting diodes having an emission with a peak emission wavelength in the range of 400 to 490 nm and the fluorescent material comprises at least one phosphor, that is a ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x
• a yellow to red light illumination system wherein the radiation source is selected from the light emitting diodes having an emission with a peak emission wavelength in the UV-range of 200 to 400 nm and the fluorescent material comprises at least one phosphor that is a ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein O ⁇ x ⁇ ljO ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2; 0 ⁇ a ⁇ 2;0 ⁇ b ⁇ 2;0 ⁇ c ⁇ 2; 0 ⁇ d ⁇ 7;0 ⁇ e ⁇ 2.
• the radiation source is selected from the light emitting diodes having an emission with a peak emission wavelength in the UV-range of 200 to 400 nm and the fluorescent material comprises at least one phosphor that is a ytterbium(II)-activated oxonitridosilicate of
• Another aspect of the present invention provides a phosphor capable of absorbing a part of light emitted by the radiation source and emitting light of a wavelength different from that of the absorbed light; wherein said phosphor is a ytterbium(II)-activated oxonitridosilicate of general formula (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein O ⁇ x ⁇ l; O ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2; 0 ⁇ a ⁇ 2; 0 ⁇ b ⁇ 2;0 ⁇ c ⁇ 2;0 ⁇ d ⁇ 7;0 ⁇ e ⁇ 2.
• the fluorescent material is excitable by UV-A emission, which has such wavelengths as from 200 nm to400 nm, but is excited with higher efficiency by blue light emitted by a blue light emitting diode having a wavelength around 400 to 490 nm.
• the fluorescent material has ideal characteristics for conversion of blue light of nitride semiconductor light emitting component into white light.
• These phosphors are broadband emitters wherein the visible emission is so broad that there is no 80 nm wavelength range where the visible emission is predominantly located.
• These ytterbium(II)-activated oxonitridosilicate phosphors emit a broad band in the red to yellow spectral range of the visible spectrum with very high efficiency. Total conversion efficiency can be up to 90 %.
• Additional important characteristics of the phosphors include 1) resistance to thermal quenching of luminescence at typical device operating temperatures (e.g.80°C); 2) lack of interfering reactivity with the encapsulating resins used in the device fabrication; 3) suitable absorptive profiles to minimize dead absorption within the visible spectrum; 4) a temporally stable luminous output over the operating lifetime of the device and; 5) compositionally controlled tuning of the phosphors excitation and emission properties.
• ytterbium(II)-activated oxonitridosilicate type phosphors may also include europium(II) and other cations including mixtures of cations as co-activators.
• the invention relates to specific phosphor composition
• These phosphors may have a coating selected from the group of fluorides and orthophosphates of the elements aluminum, scandium, yttrium, lanthanum gadolinium and lutetium, the oxides of aluminum, yttrium and lanthanum and the nitride of aluminum.
• the present invention focuses an a ytterbium(II)-activated oxonitridosilicate as a phosphor in any configuration of an illumination system containing a radiation source, including, but not limited to discharge lamps, fluorescent lamps, LEDs, LDs and X-ray tubes.
• a radiation source including, but not limited to discharge lamps, fluorescent lamps, LEDs, LDs and X-ray tubes.
• the term "radiation” encompasses preferably radiation in the UV and visible regions of the electromagnetic spectrum. While the use of the present phosphor is contemplated for a wide array of illumination, the present invention is described with particular reference to and finds particular application to light emitting diodes, especially UV- and blue-light-emitting diodes.
• the fluorescent material according to the invention comprises as an ytterbium(II)-activated oxonitridosilicate.
• the phosphor conforms to the general formula (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein O ⁇ x ⁇ l; O ⁇ y ⁇ l;
• This class of phosphor material is based an activated luminescence of a substituted oxonitridosilicate.
• the phosphor of general (Sr 1-x-y-z Ca x Ba y ) a Si b Al c N d O e :Yb z , wherein 0 ⁇ x
• ⁇ l; O ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2;0 ⁇ a ⁇ 2; 0 ⁇ b ⁇ 2;0 ⁇ c ⁇ 2;0 ⁇ d ⁇ 7;0 ⁇ e ⁇ 2 comprises a host lattice with the main components of silicon, nitrogen and oxygen in layers of (Si2N2 ⁇ 2) 2 ⁇ units, that consist of SiON 3 -tetrahedrons, which are linked to form a two-dimensional framework.
• the N atom bridges three Si atoms, while the O atom is bound terminally to the Si atom.
• Al-O-units may substitute Si-N-units.
• Six oxygen atoms coordinate the earth alkaline cations of strontium, calcium and barium as well as ytterbium and eventually a co-activator in a distorted trigonal prismatic manner.
• Fig. 4 shows the crystal structure of the basic host lattice wherein the strontium cations may be replaced by ytterbium(II)-cations.
• the host lattice for those materials may be five element (two cations) oxonitridosilicate such as ytterbium(II)-activated oxonitridosilicate Sr2Si2N2 ⁇ 2:Yb, for example, or may comprise more that five elements such as ytterbium(II)-activated calcium-strontium- oxonitridosilicate (Sr,Ca)2Si2N2 ⁇ 2:Yb for example.
• oxonitridosilicate such as ytterbium(II)-activated oxonitridosilicate Sr2Si2N2 ⁇ 2:Yb
• Sr,Ca calcium-strontium- oxonitridosilicate
• divalent earth alkaline metal ions of calcium, strontium and barium by divalent rare earth metals such as europium(II) is possible.
• the proportion z of ytterbium(II) is preferably in a range of 0.00 K z ⁇
• Density quenching refers to the decrease in emission intensity, which occurs when the concentration of an activation agent added to increase the luminance of the fluorescent material is increased beyond an optimum level.
• ytterbium(II)-activated oxonitridosilicate phosphors are responsive to more energetic portions of the electromagnetic spectrum than the visible portion of the spectrum.
• the phosphors according to the invention are especially excitable by a radiation source providing UV-emission with such wavelengths as 200 to 400 nm, such as an UV-LED, but is excited with higher efficiency by a radiation source providing blue having a wavelength from 400 to 490 nm, such as an blue-emitting LED.
• the fluorescent material has ideal characteristics for converting blue light of nitride semiconductor light emitting diodes into white light.
• the method for producing an ytterbium(II)-activated oxonitridosilicate phosphor of the present invention is not particularly restricted, and it can be produced by firing a mixture of starting materials, which provides an ytterbium(II)-activated oxonitridosilicate fluorescent material.
• starting materials which provides an ytterbium(II)-activated oxonitridosilicate fluorescent material.
• one of the preferable compound represented by SrSi 2 NiOiIYb 2+ is produced by the method where ytterbium oxide, strontium carbonate and silicon nitride as the starting materials are weighed and compounded to give a molar ratio of by SrSi 2 N 2 O 2 :Yb2% and then be fired.
• Starting materials having a high purity of 99.9% or more and in the form of fine particle having an average particle size of 1 ⁇ m or less can be preferably used.
• the staring materials i.e., alkaline earth carbonates, ytterbium compounds such as the oxide, and a silicon-nitrogen compound such as silicon diimide or silicon nitride
• the staring materials are well mixed by a dry and/or wet process utilizing any of various known mixing method such as ball mills, V-shaped mixers, stirrers and the like.
• the obtained mixture is placed in a heat-resistance container such as an alumina crucible and a tungsten boat, and then fired in an electric furnace.
• a preferred temperature for the firing ranges from 1,200 to 1,500 degree C.
• the firing atmosphere is not particularly restricted, and for example, it is preferable to conduct firing in a reducing atmosphere such as an atmosphere comprising inert gas such as nitrogen and argon and the like, and hydrogen in a proportion of 0.1 to 10 volume%.
• the firing period is determined upon various conditions such as the amount of the mixture charged in the container, the firing temperature and the temperature at which the product is taken out of the furnace, but generally in the range of2 to 4 hours.
• Fluorescent material obtained by the above-mentioned method may be ground by using, for example, a ball mill, jet mill and the like. Moreover, washing and classification may be conducted. For enhancing the cristallinity of the resulting granular phosphor re-firing is suggested.
• Fig. 2 shows the X-ray diffraction data of SrSi 2 N 2 O 2
• Fig. 3 the X-ray diffraction data of SrSi 2 N 2 O 2 : Yb 2+ .
• Each phosphor of the ytterbium(II)-activated oxonitridosilicate type emits a yellow to red fluorescence when excited by radiation of the UVA or blue range of the electromagnetic spectrum.
• the ytterbium(II)-activated oxonitridosilicate type phosphors according to the invention may be coated with a thin, uniform protective layer of one or more compounds selected from the group formed by the fluorides and orthophosphates of the elements aluminum, scandium, yttrium, lanthanum gadolinium and lutetium, the oxides of aluminum, yttrium and lanthanum and the nitride of aluminum.
• the protective layer thickness customarily ranges from 0.001 to 0.2 gm and, thus, is so thin that it can be penetrated by the radiation of the radiation source without substantial loss of energy.
• the coatings of these materials on the phosphor particles can be applied, for example, by deposition from the gas phase a wet-coating process.
• the invention also concerns an illumination system comprising a radiation source and a fluorescent material comprising at least one ytterbium(II)- activated oxonitridosilicate of general formula (Sr 1-x-y-z Ca x Bay) a SibAl c NdO e :Ybz, wherein O ⁇ x ⁇ lj O ⁇ y ⁇ l; 0.001 ⁇ z ⁇ 0.2; 0 ⁇ a ⁇ 2; 0 ⁇ b ⁇ 2; 0 ⁇ c ⁇ 2; 0 ⁇ d ⁇ 7; 0 ⁇ e ⁇ 2.
• Radiation sources include semiconductor optical radiation emitters and other devices that emit optical radiation in response to electrical excitation.
• Semiconductor optical radiation emitters include light emitting diode LED chips, light emitting polymers (LEPs), organic light emitting devices (OLEDs), polymer light emitting devices (PLEDs), etc.
• light emitting components such as those found in discharge lamps and fluorescent lamps, such as mercury low and high pressure discharge lamps, sulfur discharge lamps, and discharge lamps based an molecular radiators are also contemplated for use as radiation sources with the present inventive phosphor compositions.
• the radiation source is a light-emitting diode (LED).
• any configuration of an illumination system which includes a light emitting diode and a ytterbium(II) activated oxonitridosilicate phosphor composition is contemplated in the present invention, preferably with addition of other well-known phosphors, which can be combined to achieve a specific color or white light when irradiated by a LED emitting primary UV or blue light as specified above.
• FIG. 1 shows a schematic view of a chip type light emitting diode with a coating comprising the fluorescent material.
• the device comprises chip type light emitting diode (LED) 1 as a radiation source.
• the light-emitting diode dice is positioned in a reflector cup lead frame 2.
• the dice 1 is connected via a bond wire 7 to a first terminal 6, and directly to a second electric terminal 6.
• the recess of the reflector cup is filled with a coating material that contains a fluorescent material according to the invention to form a coating layer that is embedded in the reflector cup.
• the phosphors 3, 4 are applied either separately or in a mixture.
• the coating material typically comprises a polymer 5 for encapsulating the phosphor or phosphor blend.
• the phosphor or phosphor blend should exhibit high stability properties against the encapsulant.
• the polymer is optically clear to prevent significant light scattering.
• the polymer is selected from the group consisting of epoxy and silicone resins. Adding the phosphor mixture to a liquid that is a polymer precursor can perform encapsulation.
• the phosphor mixture can be a granular powder. Introducing phosphor particles into polymer precursor liquid results in formation of a slurry (i.e. a suspension of particles). Upon polymerization, the phosphor mixture is fixed rigidly in place by the encapsulation.
• both the fluorescent material and the LED dice are encapsulated in the polymer.
• the transparent coating material may comprise light-diffusing particles, advantageously so-called diffusers.
• diffusers are mineral fillers, in particular CaF2, Ti ⁇ 2, Si ⁇ 2, CaC ⁇ 3 or BaS ⁇ 4 or any else organic pigments. These materials can be added in a simple manner to the above-mentioned resins. In operation, electrical power is supplied to the dice to activate the dice.
• the dice When activated, the dice emits the primary light, e.g. blue light. A portion of the emitted primary light is completely or partially absorbed by the fluorescent material in the coating layer.
• the fluorescent material then emits secondary light, i.e., the converted light having a longer peak wavelength, primarily yellow in a sufficiently broadband (specifically with a significant proportion of red) in response to absorption of the primary light.
• the remaining unabsorbed portion of the emitted primary light is transmitted through the fluorescent layer, along with the secondary light.
• the encapsulation directs the unabsorbed primary light and the secondary light in a general direction as output light.
• the output light is a composite light that is composed of the primary light emitted from the die and the secondary light emitted from the fluorescent layer.
• the color temperature or color point of the output light of an illumination system according to the invention will vary depending upon the spectral distributions and intensities of the secondary light in comparison to the primary light. Firstly, the color temperature or color point of the primary light can be varied by a suitable choice of the light emitting diode.
• the color temperature or color point of the secondary light can be varied by a suitable choice of the phosphor in the luminescent material, its particle size and its concentration. Furthermore, these arrangements also advantageously afford the possibility of using phosphor blends in the luminescent material, as a result of which, advantageously, the desired hue can be set even more accurately.
• the output light of the illumination system may have a spectral distribution such that it appears to be "white" light.
• a white-light emitting illumination system can advantageously be produced by choosing the luminescent material such that a blue radiation emitted by a blue light emitting diode is converted into complementary wavelength ranges, to form dichromatic white light.
• yellow light is produced by means of the luminescent materials that comprise an ytterbium(II)-activated oxonitridosilicate phosphor.
• a second fluorescent material can be used, in addition, in order to improve the color rendition of this illumination system. Particularly good results are achieved with a blue LED whose emission maximum lies at 400 to 490 nm. An optimum has been found to lie at 445 to 468 nm, taking particular account of the excitation spectrum of the ytterbium(II)-activated oxonitridosilicate.
• a white-light emitting illumination system can particularly preferably be realized by admixing the inorganic luminescent material SrSi 2 NiOiIYb 2+ with a silicon resin used to produce the luminescence conversion encapsulation or layer. Part of a blue radiation emitted by a 462nm InGaN light emitting diode is shifted by the inorganic luminescent material SrSi 2 N 2 O 2 IYb 2+ into the orange spectral region and, consequently, into a wavelength range which is complementarily colored with respect to the color blue. A human observer perceives the combination of blue primary light and the secondary light of the yellow-emitting phosphor as white light.
• FIG. 6 shows the emission spectra of such illumination system comprising blue emitting InGaN die with primary emission at 462 nm and SrSi 2 N 2 O 2 :Yb 2+ as the fluorescent material, which together form an overall spectrum which conveys a white color sensation of high quality.
• the white output light generated by the illumination system has a significant additional amount of red color, as compared to the output light generated by the prior art LED.
• a white-light emitting illumination system can advantageously be produced by choosing the luminescent material such that a blue radiation emitted by the blue light emitting diode is converted into complementary wavelength ranges, to form polychromatic white light.
• yellow light is produced by means of the luminescent materials that comprise a blend of phosphors including ytterbium(II)-activated oxonitridosilicate phosphor and a second phosphor.
• the luminescent materials may be a blend of two phosphors, a yellow to red ytterbium(II) activated oxonitridosilicate phosphor and a red phosphor selected from the group (Ca 1-x Sr x ) S: Eu, wherein 0 ⁇ x ⁇ 1 and
• the luminescent materials may be a blend of two phosphors, e.g. a yellow to red ytterbium(II) activated oxonitridosilicate phosphor and a green phosphor selected from the group comprising (Baj_ ⁇ Sr x )2 Si ⁇ 4: Eu, wherein 0 ⁇ x ⁇ 1, SrGa2S4 :Eu and SrSi2N2U2:Eu.
• a yellow to red ytterbium(II) activated oxonitridosilicate phosphor and a green phosphor selected from the group comprising (Baj_ ⁇ Sr x )2 Si ⁇ 4: Eu, wherein 0 ⁇ x ⁇ 1, SrGa2S4 :Eu and SrSi2N2U2:Eu.
• the luminescent materials may be a blend of three phosphors, e.g. a yellow to red ytterbium(II) activated oxonitridosilicate phosphor, a red phosphor selected from the group (Ca 1-x Sr x ) S:Eu, wherein 0 ⁇ x ⁇ 1 and (Sr 1-x-y Ba x Ca y ) 2 Si 5- a Al a N 8-a O a :Eu wherein 0 ⁇ a ⁇ 5, 0 ⁇ x ⁇ land O ⁇ y ⁇ l and a yellow to green phosphor selected from the group comprising (Baj_xSr x )2 SiC ⁇ : Eu, wherein 0 ⁇ x ⁇ 1, SrGa2S4 :Eu and SrSi2N2U2:Eu.
• a white-light emitting illumination system can particularly preferably be realized by admixing the inorganic luminescent material comprising a mixture of three phosphors with a silicon resin used to produce the luminescence conversion encapsulation or layer.
• a first phosphor (1) is the yellow- emitting oxonitridosilicate SrSi 2 N 2 O 2 IYb 2+
• the second phosphor (2) is the red-emitting CaS: Eu
• the third (3) is a green-emitting phosphor of type SrSi2N2U2:Eu.
• Part of a blue radiation emitted by a 462nm InGaN light emitting diode is shifted by the inorganic luminescent material SrSi 2 N 2 O 2 : Yb 2+ into the yellow spectral region and, consequently, into a wavelength range which is complementarily colored with respect to the color blue.
• Another part of blue radiation emitted by a 462nm InGaN light emitting diode is shifted by the inorganic luminescent material CaS: Eu into the red spectral region.
• Still another part of blue radiation emitted by a 462nm InGaN light emitting diode is shifted by the inorganic luminescent material SrSi2N2 ⁇ 2:Eu into the green spectral region.
• a human observer perceives the combination of blue primary light and the polychromatic secondary light of the phosphor blend as white light.
• the hue (color point in the CIE chromaticity diagram) of the white light thereby produced can in this case be varied by a suitable choice of the phosphors in respect of mixture and concentration.
• a white-light emitting illumination system can advantageously be produced by choosing the luminescent material such that a UV radiation emitted by the UV light emitting diode is converted into complementary wavelength ranges, to form dichromatic white light.
• the yellow and blue light is produced by means of the luminescent materials.
• Yellow light is produced by means of the luminescent materials that comprise an ytterbium(II)-activated oxonitridosilicate phosphor.
• Blue light is produced by means of the luminescent materials that comprise a blue phosphor selected from the group comprising BaMgAl 10 0 17: Eu, Ba 5 SiO 4 (Cl 5 Br) 6 : Eu, CaLn 2 S ⁇ Ce and (Sr 5 Ba 5 Ca) 5 (PO 4 ) 3 Cl:Eu.
• a blue phosphor selected from the group comprising BaMgAl 10 0 17: Eu, Ba 5 SiO 4 (Cl 5 Br) 6 : Eu, CaLn 2 S ⁇ Ce and (Sr 5 Ba 5 Ca) 5 (PO 4 ) 3 Cl:Eu.
• a UVA light emitting diode whose emission maximum lies at 200 to 400 nm.
• An optimum has been found to lie at 365 nm, taking particular account of the excitation spectrum of the ytterbium(II)-activated oxonitridosilicate.
• a white-light emitting illumination system can advantageously be produced by choosing the luminescent material such that UV radiation emitted by a UV emitting diode is converted into complementary wavelength ranges, to form polychromatic white light e.g. by additive color triads, for example blue, green and red.
• the yellow to red, the green and blue light is produced by means of the luminescent materials.
• a second red fluorescent material can be used, in addition, in order to improve the color rendition of this illumination system.
• the luminescent materials may be a blend of three phosphors, a yellow to red ytterbium(II) activated oxonitridosilicate phosphor, a blue phosphor selected from the group comprising BaMgAl 10 0 17: Eu, Ba 5 SiO 4 (Cl 5 Br) 6 :Eu, CaLn 2 S ⁇ Ce and (Sr 5 Ba 5 Ca) 5 (PO 4 ) 3 Cl:Eu and a yellow to green phosphor selected from the group comprising (Baj_xSr x )2 SiO ⁇ Eu 5 wherein 0 ⁇ x ⁇ I 5 SrGa2S4 :Eu and SrSi2N2 ⁇ 2:Eu.
• a blue phosphor selected from the group comprising BaMgAl 10 0 17: Eu, Ba 5 SiO 4 (Cl 5 Br) 6 :Eu, CaLn 2 S ⁇ Ce and (Sr 5 Ba 5 Ca) 5 (PO 4 ) 3 Cl
• the hue (color point in the CIE chromaticity diagram) of the white light thereby produced can in this case be varied by a suitable choice of the phosphors in respect of mixture and concentration.
• an illumination system that emits output light having a spectral distribution such that it appears to be "yellow to red” light is contemplated.
• Fluorescent material comprising ytterbium(II) activated oxonitridosilicate as phosphor is particularly well suited as a yellow to red component for stimulation by a primary UVA or blue radiation source such as, for example, an UVA-emitting LED or blue-emitting LED. It is possible thereby to implement an illumination system emitting in the yellow to red regions of the electromagnetic spectrum.
• a yellow-light emitting illumination system can advantageously be produced by choosing the luminescent material such that a blue radiation emitted by the blue light emitting diode is converted into complementary wavelength ranges, to form dichromatic yellow to red light.
• yellow to red light is produced by means of the luminescent materials that comprise an ytterbium(II)-activated oxonitridosilicate phosphor.
• the color output of the LED - phosphor system is very sensitive to the thickness of the phosphor layer, if the phosphor layer is thick and comprises an excess of a yellow ytterbium(II) activated oxonitridosilicate phosphor, then a lesser amount of the blue LED light will penetrate through the thick phosphor layer. The combined LED - phosphor system will then appear yellow to red, because it is dominated by the yellow to red secondary light of the phosphor. Therefore, the thickness of the phosphor layer is a critical variable affecting the color output of the system. The hue (color point in the CIE chromaticity diagram) of the yellow to red light thereby produced can in this case be varied by a suitable choice of the phosphor in respect of mixture and concentration.
• a yellow-to orange light emitting illumination system can particularly preferably be realized by admixing an excess of the inorganic luminescent material SrSi2N2 ⁇ 2:Yb 2+ with a silicon resin used to produce the luminescence conversion encapsulation or layer.
• the blue radiation emitted by a 462nm InGaN light emitting diode is shifted by the inorganic luminescent material SrSi 2 NiOiIYb 2+ into the yellow to orange spectral region and, consequently, into a wavelength range which is complementarily colored with respect to the color blue.
• a human observer perceives the combination of blue primary light and the excess secondary light of orange -emitting phosphor as yellow to range light.
• a yellow to red-light emitting illumination system can advantageously be produced by choosing the luminescent material such that a UV radiation emitted by the UV emitting diode is converted entirely into monochromatic yellow to red light.
• the yellow to red light is produced by means of the luminescent materials.
• a yellow-light emitting illumination system can particularly preferably be realized by admixing the inorganic luminescent material SrSi 2 N 2 OiIYb 2+ with a silicon resin used to produce the luminescence conversion encapsulation or layer. Part of a UV radiation emitted by a UV emitting diode is shifted by the inorganic luminescent material SrSi 2 N 2 O 2 :Yb 2+ into the orange spectral region. A human observer perceives the combination of UVA primary radiation and the secondary light of the orange-emitting phosphor as yellow to orange light.
• FIG. 1 shows a schematic view of a dichromatic white LED lamp comprising a phosphor of the present invention positioned in a pathway of light emitted by an LED structure.
• FIG. 2 shows the XRD pattern of SrSi 2 N 2 Oi measured by Cu Ka radiation.
• FIG. 3 shows the XRD pattern of SrSi 2 N 2 O 2 : Yb 2+ measured by Cu Ka radiation.
• FIG. 4 shows the layered structure of the host lattice SrSi 2 N 2 O 2 .
• FIG. 6 shows the spectral radiance of an illumination system comprising a blue LED and SrSi 2 N 2 O 2 :Yb 2+ as fluorescent material.

Landscapes

• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Luminescent Compositions (AREA)
• Vessels And Coating Films For Discharge Lamps (AREA)

Priority Applications (1)

Applications Claiming Priority (3)

Publications (1)

Family

ID=36123461

Family Applications (1)

Country Status (5)

Families Citing this family (5)

Family Cites Families (5)

• 2005
  • 2005-11-23 CN CNA2005800416478A patent/CN101072843A/zh active Pending
  • 2005-11-23 EP EP05819206A patent/EP1819799A1/en not_active Withdrawn
  • 2005-11-23 JP JP2007543948A patent/JP2008521994A/ja not_active Abandoned
  • 2005-11-23 WO PCT/IB2005/053880 patent/WO2006059260A1/en active Application Filing
  • 2005-11-30 TW TW094142188A patent/TW200628590A/zh unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events