WO2009083867A1 - Color filter for a light emitting device - Google Patents
Color filter for a light emitting device Download PDFInfo
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- WO2009083867A1 WO2009083867A1 PCT/IB2008/055351 IB2008055351W WO2009083867A1 WO 2009083867 A1 WO2009083867 A1 WO 2009083867A1 IB 2008055351 W IB2008055351 W IB 2008055351W WO 2009083867 A1 WO2009083867 A1 WO 2009083867A1
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- Prior art keywords
- color filter
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- light emitting
- lighting
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/22—Absorbing filters
- G02B5/226—Glass filters
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
- H10H20/80—Constructional details
- H10H20/84—Coatings, e.g. passivation layers or antireflective coatings
Definitions
- the invention relates to color filters, especially color filters for an electroluminescent device having a phosphor layer for converting light and a filter layer for partly absorbing the converted light.
- This invention relates to color filters, especially for color filters for phosphor converted light emitting diodes (pcLEDs). It also concerns the application of these pcLEDs in light sources for LCD backlighting, automotive lighting, projection and signaling purposes.
- pcLEDs phosphor converted light emitting diodes
- pcLEDs are either white pcLEDs for illumination purposes or so-called full conversion pcLEDs.
- the latter ones are applied as green and red light sources, whereby the color point is a result of the additive color mixing of the blue radiation emitted by the semiconductor, which was not absorbed by the phosphor and the green to red emission of the luminescent screen, excited by the blue LED light.
- This is a consequence of the difficulty to completely suppress leakage of blue radiation through the luminescent screen without sacrificing overall radiant efficiency of the light source.
- color filters have been suggested, e.g. in the WO2007/039849, which is hereby incorporated by reference.
- pcLEDs with a color filter are their improved color points being closer to the boundaries of the color triangle. Therefore these pcLEDs might enter application areas by meeting requirements on the color point by the given application, e.g. signaling or LCD backlighting or other display applications. Moreover, the combination of a conversion layer with a color filter can result in colored pcLEDs with a higher package gain and thus wall plug efficiency.
- a color filter is provided essentially made out of a ceramic and/or glass material and comprising Pr and/or Nd as one optically active component.
- essentially means especially that > 90 %, preferably > 95 % and most preferred > 99 % of the material has the desired structure and/or composition.
- some additives such as binders or fluxes may be present in the color filter These additives may be incorporated fully or in part into the final material, which then may also be a composite of several chemically different species and particularly include such species known to the art as fluxes and/or binders.
- Suitable fluxes and/or binders include alkaline earth - or alkaline - metal oxides (e.g. MgO) and fluorides, Si ⁇ 2 and the like.
- ceramic material in the sense of the present invention means and/or includes especially a crystalline or polycrystalline compact material or composite material with a controlled amount of pores or which is pore free.
- polycrystalline material in the sense of the present invention means and/or includes especially a material with a volume density larger than 90 percent of the main constituent, consisting of more than 80 percent of single crystal domains, with each domain being larger than 0.5 ⁇ m in diameter and may have different crystallo graphic orientations. The single crystal domains may be connected by amorphous or glassy material or by additional crystalline constituents.
- glass material in the sense of the present invention means and/or includes especially any materials solidified from the molten state without crystallization, containing silicates, boron oxide, aluminum oxide, or phosphorus pentoxide and other substances.
- optical active component especially means and/or includes the absorption centre in the visible wavelength area of the color filter.
- the ceramic and/or glass material allows the use within a broad temperature range and allows fabrication of filters of required optical density for the Nd and/or Pr optically active components.
- the glass material has a (added) content of alkaline oxides, BaO and/or PbO of > 10 wt- % and ⁇ 50 wt- %, preferably > 20 wt-% and ⁇ 40 wt-%.
- the glass softening temperature is > 400 0 C and ⁇ 800 0 C, preferably > 450 0 C and ⁇ 650 0 C. This allows a better handling of the material for many applications within the present invention.
- the color filter comprises a material selected out of the group comprising Me 1 RE(MOi- X W x ) 2 O 8 , RE 2 (M ⁇ i_ x W x )i +y O 6+3y with Me 1 selected out of the group comprising Li, Na, K, Cs, Rb or mixtures thereof,
- RE selected out of the group comprising Pr, Nd or mixtures thereof; x being independently selected for each compound > 0 and ⁇ 1 and y being independently selected for each compound 0, 1 or 2.
- the color filter comprises essentially out of this material.
- additives may also be present in the bulk compositions. These additives particularly include such species known to the art as fluxes. Suitable fluxes include alkaline earth - or alkaline - metal oxides and fluorides, SiO 2 and the like and mixtures thereof.
- the color filter consists essentially out of these materials.
- additives may also be present in the bulk compositions.
- These additives particularly include such species known to the art as fluxes.
- Suitable fluxes include alkaline earth - or alkaline - metal oxides and fluorides, SiO 2 and the like and mixtures thereof.
- the index of refraction of the at least one color filter is >1.4, preferably >1.7, most preferred >1.8. This has been shown to be advantageous for many applications within the present invention. It has surprisingly been found that the index of refraction may be changed voluntarily with the composition of the color filter for many application so that an "index matching" of the color filter with the further component of the light emitting device is possible in many cases.
- the photothermal stability of the color filter is >80% to ⁇ 100% after exposure of the color filter for 1000 hrs at 200 0 C with a light power density of 10W/cm 2 and an average photon energy of 2.75 eV.
- photothermal stability in the sense of the present invention especially means and/or includes the conservation of the specific absorption property under simultaneous application of heat and high intensity excitation, i.e. a photothermal stability of 100% indicates that the material is virtually unaffected by the simultaneous irradiation and heat up.
- the photothermal stability of the color filter is >82.5% to ⁇ 95%, preferably >85% to ⁇ 97%, after exposure of the color filter for 1000 hrs at 200 0 C with a light power density of 10W/cm 2 and an average photon energy of 2.75 eV.
- the thermal conductivity of the color filter at room temperature is > 0.005 W Cm 1 K "1 to ⁇ 0.75 W Cm 1 K "1
- the color filter shows a transparency for normal incidence in air of >10 % to ⁇ 85 % for light in the wavelength range from > 650 nm to ⁇ 800 nm.
- the transparency for normal incidence is in air of >20 % to ⁇ 80 % for light in the wavelength range from > 550 nm to ⁇ 1000 nm, more preferred >30 % to ⁇ 75 % and most preferred > 40% to ⁇ 70% for a light in the wavelength range from > 650 nm to ⁇ 800 nm.
- transparency in the sense of the present invention means especially that > 10% preferably >20%, more preferred >30%, most preferred >40% and ⁇ 85% of the incident light of a wavelength, which cannot be absorbed by the material, is transmitted through the sample for normal incidence in air.
- This wavelength is preferably in the range of > 650 nm and ⁇ 800 nm or > 510 nm and ⁇ 570 nm, for red and green color filters, respectively.
- the color filter material has a density of >95% and ⁇ 101% of the theoretical density.
- the color filter material has a density of >97% and ⁇ 100% of the theoretical density.
- the densities lower than 100% according to the described preferred embodiment of the present invention are preferably obtained by sintering of the material to a stage where still pores are present in the ceramic matrix. Most preferred are densities in the range >98.0% and ⁇ 99.8% with total pore volumes in the ceramic matrix within the >0.2 - ⁇ 2% range. A preferred mean pore diameter is in the >400 - ⁇ 2500 nm range.
- the present invention furthermore relates to a method of producing a material for a color filter for a light emitting device according to the present invention comprising a sintering step.
- the term "sintering step" in the sense of the present invention means especially densif ⁇ cation of a precursor powder under the influence of heat, which may be combined with the application of uniaxial or isostatic pressure, without reaching the liquid state of the main consitituents of the sintered material.
- the sintering step is pressureless, preferably in reducing or inert atmosphere.
- method furthermore comprises the step of pressing the precursor material(s) to > 50% to ⁇ 70 %, according to an embodiment of the present invention, > 55% to ⁇ 60 % of its theoretical density before sintering. It has been shown in practice that this improves the sintering steps for most materials as described with the present invention.
- the method of producing a material for a light emitting device comprises the following steps: (a) Mixing the precursor materials for the material
- a first pressing step preferably a uniaxial pressing step at >10 kN using a suitable powder compacting tool with a mould in the desired shape (e.g. rod- or pellet- shape) and/ or a cold isostatic pressing step preferably at >3000 bar to ⁇ 3500 bar.
- a suitable powder compacting tool with a mould in the desired shape (e.g. rod- or pellet- shape) and/ or a cold isostatic pressing step preferably at >3000 bar to ⁇ 3500 bar.
- a hot pressing step preferably a hot isostatic pressing step preferably at > 100 bar to ⁇ 2500 bar and preferably at a temperature of >500 0 C to ⁇ 2000 0 C and/or a hot uniaxial pressing step preferably at > 100 bar to ⁇ 2500 bar and preferably at a temperature of >500 0 C to ⁇ 2000 0 C.
- the present invention furthermore relates to a light emitting device, especially a LED comprising a color filter of the present invention.
- a compound and/or a color filter according to the present invention may be of use in a broad variety of systems and/or applications, amongst them one or more of the following: - Office lighting systems household application systems shop lighting systems, home lighting systems, accent lighting systems, - spot lighting systems, theatre lighting systems, fibre-optics application systems, projection systems, self-lit display systems, - pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, and - decorative lighting systems portable systems automotive applications green house lighting systems advertisement lighting systems
- the aforementioned components, as well as the claimed components and the components to be used in accordance with the invention in the described embodiments, are not subject to any special exceptions with respect to their size, shape, compound selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.
- Fig. 1 shows a very schematic cross-sectional view of a light emitting device according to a first embodiment of the present invention.
- Fig. 2 shows an emission spectrum of a light emitting device according to a first example of the present invention, using a color filter according to Example I together with a spectrum of a comparative light emitting device without the filter
- Fig. 3 shows an emission spectrum of a light emitting device according to a second example of the present invention, using a color filter according to Example II together with a spectrum of a comparative light emitting device without the filter
- Fig.4 shows an emission spectrum of a light emitting device according to a third example of the present invention, using a color filter according to Example III together with a spectrum of a comparative light emitting device without the filter
- Fig. 5 shows a transmission spectrum of the compound of Example IV of the present invention (cf. Fig. 4) with a thickness of 100 ⁇ m.
- Fig. 6 shows an emission spectrum of a green phosphor through a color filter according to Example IV of the present invention.
- Fig. 7 shows an emission spectrum of a further green phosphor through a color filter according to Example IV of the present invention
- Fig. 8 shows an emission spectrum of a further green phosphor through a color filter according to Example IV of the present invention
- Fig. 9 shows an emission spectrum of a further green phosphor through a color filter according to Example IV of the present invention
- Fig. 10 shows an emission spectrum of a further green phosphor through a color filter according to Example IV of the present invention Fig.
- FIG. 11 is a diagram of the CIE 1931 color coordinates of the phosphors of Figs. 6 to 10 showing the shift of the spectra due to the ceramic according to Example IV.
- Fig. 12 shows an emission spectrum of a blue LED comprising a SSONE green emitting phosphor and a ceramic according to Example IV as a color filter together with the emission spectrum of the LED without the filter.
- Fig. 1 shows a very schematic cross-sectional view of a light-emitting device according to a first embodiment of the present invention.
- a blue emitting layer e.g. a InGaN semiconductor
- a green emitting phosphor 20 and a color filter 30 are provided on top of each other and embedded in a silicone matrix 40, which is itself provided in a mirror 50 (e.g. made out of silver), which is placed in the LED housing.
- Example I refers to Pr 2 M ⁇ 3 ⁇ i2, which was made as follows:
- Pr 6 On and Mo ⁇ 3 are suspended in acetone and thoroughly milled in an agate mortar.
- Fig. 2 shows an emission spectrum of a LED comprising a 470 nm InGaN chip (blue emitting), a SrGa 2 S 4 IEu ceramic (green emitting phosphor) and a ceramic comprising the material of Example I as a color filter (dotted line) together with the emission spectrum of the LED without the filter (straight line). It can be clearly seen that the emission spectrum of the LED with the filter has less peaks and is more pronounced towards the main peak. Furthermore, a shift of the color coordinates (see Fig. 2) could be reached easily and effectfully.
- Example II refers to Pr 2 Mo 2 Og, which was made similar to the compound of Example I.
- Fig. 3 shows an emission spectrum of a LED comprising a 450 nm chip, a SrSi 2 N 2 O 2 :Eu ceramic and ceramic comprising the material of Example II as a color filter (dotted line) together with the emission spectrum of the LED without the filter (straight line).
- the emission spectrum of the LED with the filter has less peaks and is more pronounced towards the main peak.
- a shift of the color coordinates could be reached easily and effectfully.
- Example III refers to Nd 2 M ⁇ 3 ⁇ i 2 , which was made similar to the compound of Example I and II.
- Fig. 4 shows an emission spectrum of a LED comprising a 460 nm chip, a CaAlSiNs :Eu ceramic and a ceramic comprising the material of Example III as a color filter (dotted line) together with the emission spectrum of the LED without the filter (straight line).
- a shift of the color coordinates could be reached easily and effectfully.
- the Figs. 5 to 12 refer to PrPO 4 which was made the following way: A PrPO 4 precursor powder with a mean particle size of about 400 nm is admixed with a polyvinylacetate binder to a granulate, followed by uniaxial pressing to a green body and pressed cold isostatically at 3200 bar for 10 seconds. After firing in air at 600 0 C to remove the binder system, the ceramic green body is sintered for 2h at 1400 0 C, grinded and polished.
- Fig. 5 shows a transmission and reflection spectrum for a lOO ⁇ m thick Pr PO 4 ceramic (density >99% of the theoretical density). Clearly the 4f-4f transitions may be seen.
- Figs 6 to 10 show the emission spectra of several (known) phosphors through (dotted line) and without (straight line) a 240 ⁇ m thick Pr PO 4 ceramic body.
- the name and formulae of the phosphors are listed in Table I
- Fig. 11 is a diagram of the CIE 1931 color coordinates of the phosphors
- Fig. 12 shows an emission spectrum of a blue LED comprising a SSONE green emitting phosphor and a lOO ⁇ m thick Pr PO 4 ceramic as a color filter (dotted line) together with the emission spectrum of the LED without the filter (straight line).
- a coating was placed around LED-phosphor-color filter to prevent any blue light being emitted in any direction other than through the color filter. It can be clearly seen that the emission spectrum of the LED with the filter has less peaks and is more pronounced towards the main peak. Furthermore, a shift of the color coordinates (see also Fig. 11) could be reached easily and effectfully.
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Abstract
The invention relates to an improved novel color filter for light emitting devices essentially made out of a ceramic and/or glass material and comprising Pr and/or Nd as one optically active component.
Description
Color filter for a light emitting device
FIELD OF THE INVENTION
The invention relates to color filters, especially color filters for an electroluminescent device having a phosphor layer for converting light and a filter layer for partly absorbing the converted light.
BACKGROUND OF THE INVENTION
This invention relates to color filters, especially for color filters for phosphor converted light emitting diodes (pcLEDs). It also concerns the application of these pcLEDs in light sources for LCD backlighting, automotive lighting, projection and signaling purposes.
Presently applied pcLEDs are either white pcLEDs for illumination purposes or so-called full conversion pcLEDs. The latter ones are applied as green and red light sources, whereby the color point is a result of the additive color mixing of the blue radiation emitted by the semiconductor, which was not absorbed by the phosphor and the green to red emission of the luminescent screen, excited by the blue LED light. This is a consequence of the difficulty to completely suppress leakage of blue radiation through the luminescent screen without sacrificing overall radiant efficiency of the light source. For this purpose, color filters have been suggested, e.g. in the WO2007/039849, which is hereby incorporated by reference. Advantages of pcLEDs with a color filter are their improved color points being closer to the boundaries of the color triangle. Therefore these pcLEDs might enter application areas by meeting requirements on the color point by the given application, e.g. signaling or LCD backlighting or other display applications. Moreover, the combination of a conversion layer with a color filter can result in colored pcLEDs with a higher package gain and thus wall plug efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a color filter, which may be used within a wide range of applications and especially allows a shift of the color point of the light-emitting device.
This object is solved by a compound according to claim 1 of the present invention. Accordingly, a color filter is provided essentially made out of a ceramic and/or glass material and comprising Pr and/or Nd as one optically active component.
The term "essentially" means especially that > 90 %, preferably > 95 % and most preferred > 99 % of the material has the desired structure and/or composition. It should be noted that (depending on the manufacturing procedure) some additives, such as binders or fluxes may be present in the color filter These additives may be incorporated fully or in part into the final material, which then may also be a composite of several chemically different species and particularly include such species known to the art as fluxes and/or binders. Suitable fluxes and/or binders include alkaline earth - or alkaline - metal oxides (e.g. MgO) and fluorides, Siθ2 and the like.
The term "ceramic material" in the sense of the present invention means and/or includes especially a crystalline or polycrystalline compact material or composite material with a controlled amount of pores or which is pore free. The term "polycrystalline material" in the sense of the present invention means and/or includes especially a material with a volume density larger than 90 percent of the main constituent, consisting of more than 80 percent of single crystal domains, with each domain being larger than 0.5 μm in diameter and may have different crystallo graphic orientations. The single crystal domains may be connected by amorphous or glassy material or by additional crystalline constituents.
The term "glass material" in the sense of the present invention means and/or includes especially any materials solidified from the molten state without crystallization, containing silicates, boron oxide, aluminum oxide, or phosphorus pentoxide and other substances.
The term "optically active component" especially means and/or includes
the absorption centre in the visible wavelength area of the color filter.
The use of such a color filter has shown for a wide range of applications within the present invention to have at least one of the following advantages:
Due to the 4f-4f transitions of the Nd and/or Pr cations, rather narrow absorption bands with steep absorption edges can be found which make them advantageous for many applications
The ceramic and/or glass material allows the use within a broad temperature range and allows fabrication of filters of required optical density for the Nd and/or Pr optically active components.
According to a preferred embodiment of the present invention, the glass material has a (added) content of alkaline oxides, BaO and/or PbO of > 10 wt- % and < 50 wt- %, preferably > 20 wt-% and < 40 wt-%.
By doing so, it has been found for many applications that a thick optical component can be formed, in which the absorption bands of the Nd and Pr become effective, thus making the color filter more effective.
According to a further preferred embodiment of the present invention, the glass softening temperature is > 4000C and < 800 0C, preferably > 4500C and < 650 0C. This allows a better handling of the material for many applications within the present invention.
According to a preferred embodiment of the present invention, the color filter comprises a material selected out of the group comprising Me1RE(MOi-XWx)2O8, RE2(Mθi_xWx)i+yO6+3ywith Me1 selected out of the group comprising Li, Na, K, Cs, Rb or mixtures thereof,
RE selected out of the group comprising Pr, Nd or mixtures thereof; x being independently selected for each compound > 0 and < 1 and y being independently selected for each compound 0, 1 or 2. RE PO4 , K3RE(PO4)2 - K2RE Cl5, Li3RE Cl6, RE Br3, RbRE2Br7
RE OF, RE OCl, RE OBr
RE2SiO55 RE2Si2O71 LiRESiO4
RE BO3, CaRE BO4, RE B3O6, RE MgB5Oi0, CaRE B7Oi3, Li3RE2B3O9, RE Sc3B4Oi2 Sr3RE2B4Oi2
RE AlO3, (Y, RE)3Al5Oi2, REAl3B4Oi2, REMgAInOi9, RE4Al2O9 - RE2S3, (Y5RE)2O2S
RE2Ti2O7 or mixtures thereof.
Preferably the color filter comprises essentially out of this material. However, in some applications, trace amounts of additives may also be present in the bulk compositions. These additives particularly include such species known to the art as fluxes. Suitable fluxes include alkaline earth - or alkaline - metal oxides and fluorides, SiO2 and the like and mixtures thereof.
Preferably the color filter consists essentially out of these materials. However, here too, in some applications, trace amounts of additives may also be present in the bulk compositions. These additives particularly include such species known to the art as fluxes. Suitable fluxes include alkaline earth - or alkaline - metal oxides and fluorides, SiO2 and the like and mixtures thereof.
According to a preferred embodiment of the present invention, the index of refraction of the at least one color filter is >1.4, preferably >1.7, most preferred >1.8. This has been shown to be advantageous for many applications within the present invention. It has surprisingly been found that the index of refraction may be changed voluntarily with the composition of the color filter for many application so that an "index matching" of the color filter with the further component of the light emitting device is possible in many cases.
According to a preferred embodiment of the present invention, the photothermal stability of the color filter is >80% to <100% after exposure of the color filter for 1000 hrs at 2000C with a light power density of 10W/cm2 and an average photon energy of 2.75 eV. The term "photothermal stability" in the sense of the present invention especially means and/or includes the conservation of the specific absorption property
under simultaneous application of heat and high intensity excitation, i.e. a photothermal stability of 100% indicates that the material is virtually unaffected by the simultaneous irradiation and heat up.
According to a preferred embodiment of the present invention, the photothermal stability of the color filter is >82.5% to <95%, preferably >85% to <97%, after exposure of the color filter for 1000 hrs at 2000C with a light power density of 10W/cm2 and an average photon energy of 2.75 eV.
According to a preferred embodiment of the present invention, the thermal conductivity of the color filter at room temperature is > 0.005 W Cm 1K"1 to < 0.75 W Cm 1K"1
According to one embodiment of the present invention, the color filter shows a transparency for normal incidence in air of >10 % to <85 % for light in the wavelength range from > 650 nm to < 800 nm.
Preferably, the transparency for normal incidence is in air of >20 % to < 80 % for light in the wavelength range from > 550 nm to < 1000 nm, more preferred >30 % to <75 % and most preferred > 40% to < 70% for a light in the wavelength range from > 650 nm to < 800 nm.
The term "transparency" in the sense of the present invention means especially that > 10% preferably >20%, more preferred >30%, most preferred >40% and <85% of the incident light of a wavelength, which cannot be absorbed by the material, is transmitted through the sample for normal incidence in air. This wavelength is preferably in the range of > 650 nm and <800 nm or > 510 nm and <570 nm, for red and green color filters, respectively.
According to a preferred embodiment of the present invention, the color filter material has a density of >95% and < 101% of the theoretical density.
According to a preferred embodiment of the present invention, the color filter material has a density of >97% and < 100% of the theoretical density.
The densities lower than 100% according to the described preferred embodiment of the present invention are preferably obtained by sintering of the material to a stage where still pores are present in the ceramic matrix. Most preferred are densities in the range >98.0% and <99.8% with total pore volumes in the ceramic matrix
within the >0.2 - <2% range. A preferred mean pore diameter is in the >400 - < 2500 nm range.
The present invention furthermore relates to a method of producing a material for a color filter for a light emitting device according to the present invention comprising a sintering step.
The term "sintering step" in the sense of the present invention means especially densifϊcation of a precursor powder under the influence of heat, which may be combined with the application of uniaxial or isostatic pressure, without reaching the liquid state of the main consitituents of the sintered material. According to an embodiment of the present invention, the sintering step is pressureless, preferably in reducing or inert atmosphere.
According to an embodiment of the present invention, method furthermore comprises the step of pressing the precursor material(s) to > 50% to < 70 %, according to an embodiment of the present invention, > 55% to < 60 % of its theoretical density before sintering. It has been shown in practice that this improves the sintering steps for most materials as described with the present invention.
According to an embodiment of the present invention, the method of producing a material for a light emitting device according to the present invention comprises the following steps: (a) Mixing the precursor materials for the material
(b) optional firing of the precursor materials, preferably at a temperature of >500°C to < 15000C to remove volatile materials
(c) optional grinding and washing
(d) a first pressing step, preferably a uniaxial pressing step at >10 kN using a suitable powder compacting tool with a mould in the desired shape (e.g. rod- or pellet- shape) and/ or a cold isostatic pressing step preferably at >3000 bar to < 3500 bar.
(e) a pressureless sintering step at >500 0C to < 17000C
(f) a hot pressing step, preferably a hot isostatic pressing step preferably at > 100 bar to < 2500 bar and preferably at a temperature of >500 0C to < 20000C and/or a hot uniaxial pressing step preferably at > 100 bar to < 2500 bar and preferably at
a temperature of >500 0C to < 20000C.
(g) optionally a post annealing step at >500°C to < 17000C in inert atmosphere or air.
The present invention furthermore relates to a light emitting device, especially a LED comprising a color filter of the present invention.
A compound and/or a color filter according to the present invention may be of use in a broad variety of systems and/or applications, amongst them one or more of the following: - Office lighting systems household application systems shop lighting systems, home lighting systems, accent lighting systems, - spot lighting systems, theatre lighting systems, fibre-optics application systems, projection systems, self-lit display systems, - pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, and - decorative lighting systems portable systems automotive applications green house lighting systems advertisement lighting systems The aforementioned components, as well as the claimed components and the components to be used in accordance with the invention in the described
embodiments, are not subject to any special exceptions with respect to their size, shape, compound selection and technical concept such that the selection criteria known in the pertinent field can be applied without limitations.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional details, features, characteristics and advantages of the object of the invention are disclosed in the sub claims, the figures and the following description of the respective figures and examples, which —in an exemplary fashion— show several embodiments and examples of inventive compounds
Fig. 1 shows a very schematic cross-sectional view of a light emitting device according to a first embodiment of the present invention.
Fig. 2 shows an emission spectrum of a light emitting device according to a first example of the present invention, using a color filter according to Example I together with a spectrum of a comparative light emitting device without the filter
Fig. 3 shows an emission spectrum of a light emitting device according to a second example of the present invention, using a color filter according to Example II together with a spectrum of a comparative light emitting device without the filter
Fig.4 shows an emission spectrum of a light emitting device according to a third example of the present invention, using a color filter according to Example III together with a spectrum of a comparative light emitting device without the filter
Fig. 5 shows a transmission spectrum of the compound of Example IV of the present invention (cf. Fig. 4) with a thickness of 100 μm. Fig. 6 shows an emission spectrum of a green phosphor through a color filter according to Example IV of the present invention. Fig. 7 shows an emission spectrum of a further green phosphor through a color filter according to Example IV of the present invention
Fig. 8 shows an emission spectrum of a further green phosphor through a color filter according to Example IV of the present invention Fig. 9 shows an emission spectrum of a further green phosphor through a color filter according to Example IV of the present invention Fig. 10 shows an emission spectrum of a further green phosphor through a color filter according to Example IV of the present invention Fig. 11 is a diagram of the CIE 1931 color coordinates of the phosphors of Figs. 6 to 10 showing the shift of the spectra due to the ceramic according to Example IV. Fig. 12 shows an emission spectrum of a blue LED comprising a SSONE green emitting phosphor and a ceramic according to Example IV as a color filter together with the emission spectrum of the LED without the filter.
Fig. 1 shows a very schematic cross-sectional view of a light-emitting device according to a first embodiment of the present invention. In this light emitting device 1, a blue emitting layer (e.g. a InGaN semiconductor) 10,. a green emitting phosphor 20 and a color filter 30 are provided on top of each other and embedded in a silicone matrix 40, which is itself provided in a mirror 50 (e.g. made out of silver), which is placed in the LED housing.
The invention will be further understood by the following Examples I to IV which - in a merely illustrative fashion - show several compounds for a color filter for use in a light emitting device of the present invention.
EXAMPLE I:
Example I refers to Pr2Mθ3θi2, which was made as follows:
Pr6On and Moθ3 are suspended in acetone and thoroughly milled in an agate mortar.
Afterwards the blend was dried in a drying furnace at 1000C for 1 h. The dried blend was subsequently annealed in aluminum crucibles at 10000C in a CO atmosphere. Finally, the obtained powder cake is milled again and fired at 10000C for 2 h in air. The ceramic body is sintered for 2h at 14000C, grinded and polished.
Fig. 2 shows an emission spectrum of a LED comprising a 470 nm InGaN chip (blue emitting), a SrGa2S4IEu ceramic (green emitting phosphor) and a ceramic comprising the material of Example I as a color filter (dotted line) together with the emission spectrum of the LED without the filter (straight line). It can be clearly seen that the emission spectrum of the LED with the filter has less peaks and is more pronounced towards the main peak. Furthermore, a shift of the color coordinates (see Fig. 2) could be reached easily and effectfully.
EXAMPLE II: Example II refers to Pr2Mo2Og, which was made similar to the compound of Example I. Fig. 3 shows an emission spectrum of a LED comprising a 450 nm chip, a SrSi2N2O2 :Eu ceramic and ceramic comprising the material of Example II as a color filter (dotted line) together with the emission spectrum of the LED without the filter (straight line). Here, too, the emission spectrum of the LED with the filter has less peaks and is more pronounced towards the main peak. Furthermore, a shift of the color coordinates (see Fig. 3) could be reached easily and effectfully.
EXAMPLE III:
Example III refers to Nd2Mθ3θi2, which was made similar to the compound of Example I and II.
Fig. 4 shows an emission spectrum of a LED comprising a 460 nm chip, a CaAlSiNs :Eu ceramic and a ceramic comprising the material of Example III as a color filter (dotted line) together with the emission spectrum of the LED without the filter (straight line). Here, too, a shift of the color coordinates (see Fig. 3) could be reached easily and effectfully.
EXAMPLE IV:
The Figs. 5 to 12 refer to PrPO4 which was made the following way: A PrPO4 precursor powder with a mean particle size of about 400 nm is admixed with a polyvinylacetate binder to a granulate, followed by uniaxial pressing to a green body and pressed cold isostatically at 3200 bar for 10 seconds. After firing in air at 6000C to
remove the binder system, the ceramic green body is sintered for 2h at 14000C, grinded and polished.
Fig. 5 shows a transmission and reflection spectrum for a lOOμm thick Pr PO4 ceramic (density >99% of the theoretical density). Clearly the 4f-4f transitions may be seen.
Figs 6 to 10 show the emission spectra of several (known) phosphors through (dotted line) and without (straight line) a 240μm thick Pr PO4 ceramic body. The name and formulae of the phosphors are listed in Table I
Table I
, No. Phosphor Formula Abbr. in Fig. 11
(abbr.)
6 BSONE Ba0 C18Si2O2N2 :Eu0 02 Pl
7 BOSE (Ba5Sr)2SiO4 P2
8 LuAG Lu2 88Al5Oi2:Ceo i2 P3
9 YAG Y2 58Gd0 3Al5Oi2ICe0 I2 P4
10 SSONE Sr0 98Si2O2N2IEu0 02 P5
As can be clearly seen from the Figs, the peaks are sharpened for each of the phosphors, showing the high suitability of the PrPO4 ceramic. Fig. 11 is a diagram of the CIE 1931 color coordinates of the phosphors
(listed as Pl to P5, see Table I above) showing the shift of the spectra due to the PrPO4 ceramic.
Fig. 12 shows an emission spectrum of a blue LED comprising a SSONE green emitting phosphor and a lOOμm thick Pr PO4 ceramic as a color filter (dotted line) together with the emission spectrum of the LED without the filter (straight line). To achieve highest possible color purity a coating was placed around LED-phosphor-color filter to prevent any blue light being emitted in any direction other than through the color filter. It can be clearly seen that the emission spectrum of the LED with the filter has less peaks and is more pronounced towards the main peak. Furthermore, a shift of the color coordinates (see also Fig. 11) could be reached easily and effectfully.
The particular combinations of elements and features in the above detailed
embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the patents/applications incorporated by reference are also expressly contemplated. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed.
Claims
1. The color filter of claim 1, whereby the glass material has a (added) content of alkaline oxides, BaO and/or PbO of > 10 wt-% and < 50 wt-%,
2. The color filter of claim 1 or 2, whereby the glass material has a the glass softening temperature is > 4000C and < 800 0C
3. The color filter of any of the claims 1 to 3, whereby the color filter comprises a material selected out of the group comprising - Me1RE(MOi-XWx)2O8, RE2(Mθi_xWχ)i+yO6+3y with
Me1 selected out of the group comprising Li, Na, K, Cs, Rb or mixtures thereof,
RE selected out of the group comprising Pr, Nd or mixtures thereof; x being independently selected for each compound > 0 and < 1 and y being independently selected for each compound 0, 1 or 2.
- RE PO4 , K3RE(PO4)2
- K2RE Cl5, Li3RE Cl6, RE Br3, RbRE2Br7
- RE OF, RE OCl, RE OBr
- RE2SiO5, RE2Si2O7, LiRESiO4 - RE BO3, CaRE BO4, RE B3O6, RE MgB5Oi0, CaRE B7Oi3,
Li3RE2B3O9, RE Sc3B4Oi2 Sr3RE2B4Oi2
- RE AlO3, (Y, RE)3Al5Oi2, REAl3B4Oi2, REMgAInOi9, RE4Al2O9
- RE2S3, (Y5RE)2O2S
- RE2Ti2O7 or mixtures thereof.
4. The color filter of any of the claims 1 to 4, whereby the index of refraction of the at least one color filter is >1.4.
5. The color filter of any of the claims 1 to 5, whereby the photothermal stability of the color filter is >80% to <100% after exposure of the color filter for 1000 hrs at 2000C with a light power density of 10W/cm2 and an average photon energy of 2.75 eV.
6. The color filter of any of the claims 1 to 6, whereby the thermal conductivity of the color filter is > 0.005 W Cm 1K"1 to < 75W Cm 1K"1
7. The color filter of any of the claims 1 to 7, whereby the color filter material has a density of >95% and < 101% of the theoretical density.
8. A light emitting device, especially a LED comprising a color filter according to any of the claims 1 to 8.
9. A system comprising a color filter according to any of the claims 1 to 8 and/or a light emitting device of claim 9, the system being used in one or more of the following applications:
Office lighting systems household application systems - shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theatre lighting systems,
fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, - segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, and decorative lighting systems - portable systems automotive applications green house lighting systems Advertisement systems
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP07123780.4 | 2007-12-20 | ||
| EP07123780 | 2007-12-20 |
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| Publication Number | Publication Date |
|---|---|
| WO2009083867A1 true WO2009083867A1 (en) | 2009-07-09 |
Family
ID=40456251
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/IB2008/055351 Ceased WO2009083867A1 (en) | 2007-12-20 | 2008-12-16 | Color filter for a light emitting device |
Country Status (2)
| Country | Link |
|---|---|
| TW (1) | TW200949308A (en) |
| WO (1) | WO2009083867A1 (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102401919A (en) * | 2011-07-12 | 2012-04-04 | 苏州昆仑工业设计有限公司 | Doped optical filter for reducing blue light harm of LED |
| US20150357531A1 (en) * | 2014-06-05 | 2015-12-10 | Lg Electronics Inc. | Light emitting device |
| US9612002B2 (en) | 2012-10-18 | 2017-04-04 | GE Lighting Solutions, LLC | LED lamp with Nd-glass bulb |
| CN109021972A (en) * | 2018-05-31 | 2018-12-18 | 杭州电子科技大学 | A kind of white light LEDs borate blue fluorescent powder and preparation method thereof |
| WO2019000581A1 (en) * | 2017-06-29 | 2019-01-03 | 中国科学院包头稀土研发中心 | Colorant and preparation method therefor |
| US10619803B2 (en) * | 2016-03-16 | 2020-04-14 | Consumer Lighting (U.S.), Llc | LED apparatus employing neodymium based materials with variable content of fluorine and oxygen |
| WO2022069584A1 (en) * | 2020-10-01 | 2022-04-07 | Fachhochschule Münster | Material for gas discharge lamps |
| DE102020125770A1 (en) | 2020-10-01 | 2022-04-28 | FH Münster, Körperschaft des öffentlichen Rechts | Material for gas discharge lamps |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102401919A (en) * | 2011-07-12 | 2012-04-04 | 苏州昆仑工业设计有限公司 | Doped optical filter for reducing blue light harm of LED |
| US9612002B2 (en) | 2012-10-18 | 2017-04-04 | GE Lighting Solutions, LLC | LED lamp with Nd-glass bulb |
| US20150357531A1 (en) * | 2014-06-05 | 2015-12-10 | Lg Electronics Inc. | Light emitting device |
| US9455380B2 (en) * | 2014-06-05 | 2016-09-27 | Lg Electronics Inc. | High color rendering light emitting device including different phosphors |
| US10619803B2 (en) * | 2016-03-16 | 2020-04-14 | Consumer Lighting (U.S.), Llc | LED apparatus employing neodymium based materials with variable content of fluorine and oxygen |
| US10920938B2 (en) | 2016-03-16 | 2021-02-16 | Savant Technologies Llc | LED apparatus employing neodymium based materials with variable content of fluorine and oxygen |
| WO2019000581A1 (en) * | 2017-06-29 | 2019-01-03 | 中国科学院包头稀土研发中心 | Colorant and preparation method therefor |
| US11208561B2 (en) | 2017-06-29 | 2021-12-28 | Baotou Rare Earth Research And Development Center, Chinese Academy Of Sciences | Colorant and preparation method thereof |
| CN109021972A (en) * | 2018-05-31 | 2018-12-18 | 杭州电子科技大学 | A kind of white light LEDs borate blue fluorescent powder and preparation method thereof |
| CN109021972B (en) * | 2018-05-31 | 2021-03-23 | 杭州电子科技大学 | Borate blue fluorescent powder for white light LED and preparation method thereof |
| WO2022069584A1 (en) * | 2020-10-01 | 2022-04-07 | Fachhochschule Münster | Material for gas discharge lamps |
| DE102020125770A1 (en) | 2020-10-01 | 2022-04-28 | FH Münster, Körperschaft des öffentlichen Rechts | Material for gas discharge lamps |
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| Publication number | Publication date |
|---|---|
| TW200949308A (en) | 2009-12-01 |
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