LED apparatus employing neodymium-fluorine materials

Abstract

The specification and drawings present a new apparatus such as a lighting apparatus, the apparatus comprising at least one LED (or OLED) module, configured to generate a visible light such as white light, and at least one component such as optical component comprising a compound consisting essentially of the elements neodymium (Nd) and fluorine (F), and optionally including one or more other elements. The lighting apparatus is configured to provide a desired light spectrum by filtering the generated visible light using the compound.

Claims

1. An apparatus comprising: at least one light emitting diode (LED) module, configured to generate a white light; and at least one encapsulating layer configured to filter the generated white light, the at least one encapsulating layer comprising a color-filtering compound comprising a NdXF compound, wherein X is one or more of O, N, S, Cl, OH, Na, K, Al, Mg, Li, Ca, Sr, Ba or Y, blended or dispersed in silicone, and a phosphor dispersed or blended in the at least one encapsulating layer or encapsulated in a further encapsulating layer in addition to the at least one encapsulating layer; and wherein the color-filtering compound is configured to have a refractive index that is similar to that of silicone and is configured to absorb a yellow light in the wavelength range between about 530 nm and 600 nm from the generated white light.

2. The apparatus of claim 1, wherein the color-filtering compound comprises Nd.sup.3+ ions and F.sup. ions.

3. The apparatus of claim 1, wherein the at least one encapsulating layer is deposited on top of the at least one LED module to filter its generated white light.

4. The apparatus of claim 1, wherein the phosphor is encapsulated in the further encapsulating layer in addition to the at least one encapsulating layer and the further encapsulating layer containing phosphor is deposited directly on top of the at the least one LED module and the at least one encapsulating layer containing NdXF is deposited on top of the further encapsulating layer.

5. The apparatus of claim 1, wherein the color-filtering compound is NdFO.

6. The apparatus of claim 1, wherein the at least one encapsulating layer further comprises scattering particles of an organic or inorganic material, a particle size of the organic or inorganic material being in a range from about 1 nm to about 10 microns.

7. The apparatus of claim 1, further comprising a circuit connecting a plurality of LED modules, each configured to generate a white light and having an encapsulating layer configured to filter the generated white light.

8. The apparatus of claim 1, wherein X is O or OH, and the color-filtering compound is a neodymium oxyfluoride or a neodymium hydroxide fluoride.

9. An apparatus comprising: at least one light emitting diode (LED) module, configured to generate a visible light; and at least one optical component comprising a transparent, translucent or reflective substrate; and a coating on a surface of the substrate, wherein the coating comprises a color-filtering compound blended or dispersed in silicone and configured to absorb the generated visible light in a yellow light wavelength range between about 530 nm and 600 nm, said color-filtering compound comprising a NdXF compound, wherein X is one or more of O, N, S, Cl, OH, Na, K, Al, Mg, Li, Ca, Sr, Ba or Y, wherein the NdXF compound is configured to have a refractive index that is similar to that of silicone.

10. The apparatus of claim 9, wherein a weight percentage of the color-filtering compound in the coating is from about 1% to about 20%.

11. The apparatus of claim 9, wherein a thickness of the coating is in a range from about 50 nm to about 1000 microns.

12. The apparatus of claim 9, wherein the coating further comprises an additive having a higher refractive index than the color-filtering compound, and wherein the additive is selected from metal oxides and non-metal oxides.

13. The apparatus of claim 12, wherein the additive is selected from the group consisting of TiO.sub.2, SiO.sub.2 and Al.sub.2O.sub.3.

14. The apparatus of claim 9, wherein the coating is coated on an inner surface of the reflective substrate or the diffuser.

15. The apparatus of claim 9, wherein the substrate is a diffuser selected from the group consisting of a dome enclosing the at least one LED module, a bulb, and a lens.

16. The apparatus of claim 9, wherein the optical component further comprises a bonding layer between the reflective substrate or the diffuser and the coating, the bonding layer comprises an organic adhesive or an inorganic adhesive.

17. The apparatus of claim 9, wherein the coating is coated on the surface of the substrate by one of a spray coating method and an electrostatic coating method.

18. An apparatus comprising: at least one light emitting diode (LED) module, configured to generate a white light; and at least one optical component comprising a NdXF color-filtering compound dispersed or blended in silicone, wherein the NdXF color-filtering compound is configured to have has a refractive index that is similar to that of silicone to filter the generated white light in a yellow light wavelength range between about 530 nm and 600 nm, wherein X is one or more of O, N, S, Cl, OH, Na, K, Al, Mg, Li, Ca, Sr, Ba or Y.

19. The apparatus of claim 18, wherein X is one or more of N, S, Cl, OH, Na, K, Al, Mg, Li, Ca, Sr, Ba or Y.

20. The apparatus of claim 19, wherein the NdXF color-filtering compound is neodymium hydroxide fluoride.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features and aspects of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout the drawings, wherein:

(2) FIG. 1 is a perspective view of a conventional LED-based lighting apparatus;

(3) FIG. 2 is a graph comparing absorption in a visible spectrum of neodymium fluoride dispersed in silicone vs. that of standard neodymium glass;

(4) FIG. 3 is a graph comparing an emission spectrum of NdF.sub.3 blended into silicone and directly deposited on a commercial LED package (NICHIA 757), and an emission spectrum of the base NICHIA757 LED;

(5) FIG. 4 is a graph comparing an emission spectrum of NdF.sub.3 blended into silicone and directly deposited upon a COB array (TG66), and an emission spectrum of the base TG66 COB array;

(6) FIG. 5 is a graph comparing an emission spectrum of NdFO blended into silicone and directly deposited on a commercial LED package (NICHIA 757 with 4000 K CCT), and an emission spectrum of the base NICHIA757 LED;

(7) FIGS. 6a-6d are non-limiting examples of an LED-based lighting apparatus, incorporating a NdF compound (or more generally NdXF compound as described herein) along with a phosphor to impart favorable visible absorption/generation characteristics according to various embodiments of the invention.

(8) FIG. 7 is a cross-sectional view of an LED-based lighting apparatus in accordance with one embodiment of the invention;

(9) FIG. 8 is a cross-sectional view of an LED-based lighting apparatus in accordance with another embodiment of the invention;

(10) FIG. 9 is a perspective view of an LED-based lighting apparatus in accordance with a further embodiment of this invention.

(11) FIG. 10 is a perspective view of an LED-based lighting apparatus in accordance with one further embodiment of this invention.

DETAILED DESCRIPTION

(12) A new apparatus such as a lighting apparatus is presented herein, the apparatus comprising at least one LED (or OLED) module configured to generate a visible light such as white light, and at least one component such as an optical component comprising a compound comprising elements of neodymium (Nd) and fluorine (F), and optionally comprising one or more other elements. The lighting apparatus is configured to provide a desired light spectrum by filtering the generated visible light using the compound, as described herein. Typically the compound comprises Nd.sup.3+ ions and F.sup. ions. For the purpose of this invention, a NdF compound should be broadly construed to include compounds comprising neodymium and fluoride and optionally other elements.

(13) According to one embodiment, the component may include a composite/encapsulating layer on a surface of the LED (OLED) chip so that a NdF compound such as NdF.sub.3, and/or others disclosed herein, can be blended (dispersed) in that encapsulating layer, e.g., along with a phosphor, to achieve favorable visible absorption profiles. The composite/encapsulating layer may be formed using a low temperature glass, a polymer, a polymer precursor, a silicone or silicone epoxy resin or precursor, and the like.

(14) According to another embodiment, the optical component may be a transparent, translucent, reflective or transflective (partially reflective and transmitting) substrate, and a coating on a surface of the substrate can apply a color filtering effect to the visible light, generated by the LED module, while it is passing through the optical component, e.g., to filter the visible light in the yellow light wavelength range, for example, for wavelengths from about 560 nm to about 600 nm.

(15) Furthermore, the transparent or translucent substrate of the optical component may be a diffuser, such as a bulb, a lens and an envelope enclosing at least one LED chip. Moreover, the substrate may be a reflective substrate, and the LED chip can be arranged outside of the substrate. The NdF and/or NdXF compound coating may be disposed on a surface of the substrate, and the thickness of the coating should be sufficient to achieve the color filtering effect. The thickness may typically be within a range from 50 nm to 1000 microns, with a preferred thickness being between 100 nm to 500 microns.

(16) The resultant devices can exhibit improvement of light parameters using filtering with NdF compounds/materials having intrinsic absorption in the visible region between about 530 nm and 600 nm to enhance at least one of: CSI (color saturation index); CRI (color rendering index); R9 (color rendering value for a particular color chip); revealness (which is a color rendering metric understood by the artisan as referring to lighting preference index, LPI); or the like. R9 is defined as one of 6 saturated test colors not used in calculating CRI. The revealness is a parameter of the emitted light based on a version of the LPI, which is described in co-pending, commonly owned International application PCT/US2014/054868, filed Sep. 9, 2014 (published as WO2015/035425 on Mar. 12, 2015), and hereby incorporated by reference in pertinent part.

(17) In one embodiment, it is advantageous to utilize relatively low refractive index (RI) NdF materials (such as NdF.sub.3 having RI around 1.6) to match the RI of the encapsulation materials, in order to achieve a lower scattering loss in LED packages and chip-on-board (COB) arrays. Moreover, it is further advantageous to be able to tune the absorption spectrum by including an electronegative X atom in a NdXF material, where X can be, for example, O, N, S, Cl, or the like, to broaden the absorption at around 580 nm and thus possibly to enhance color rendering of an R9 color chip. Any of the foregoing may be blended into an encapsulating material for color adjustment purposes. Upon selection of an appropriate NdF or NdXF material (to be more fully defined below), the scattering losses due to RI mismatch can be minimized. The use of NdF compounds may also be advantageous for use in LED lighting applications containing short UV wavelengths, since NdF compounds are generally not activated in a wavelength range about 380-450 nm.

(18) According to another embodiment, the NdF compound may comprise neodymium fluoride (NdF.sub.3), or neodymium oxyfluoride (e.g., NdO.sub.xF.sub.y where 2x+y=3, such as Nd.sub.4O.sub.3F.sub.6.), or neodymium fluoride comprising adventitious water and/or oxygen, or a neodymium hydroxide fluoride (e.g., Nd(OH).sub.aF.sub.b where a+b=3), or numerous other compounds comprising neodymium and fluoride which will become readily apparent from the following description. In some applications, the NdF compound may have a relatively low refractive index, such as a refractive index that matches selected polymeric materials to provide a low-loss blend. One such NdF material is believed to be neodymium fluoride (NdF.sub.3), which has a refractive index of around 1.6, providing a suitably low refractive index for index matching with certain polymeric matrix materials to minimize scattering losses.

(19) According to a further embodiment, other NdF compounds/materials can be used to advantage as described herein. For instance, other compounds containing NdF, non-limiting examples of which may include NdXF compounds. In addition to the previous statement that X can be O, N, S, Cl, or the like, X can also be at least one metallic element (other than Nd) that can form a compound with fluorine. Examples are: a metallic element such as Na, K, Al, Mg, Li, Ca, Sr, Ba, or Y, or combinations of such elements. For example, a NdXF compound may comprise NaNdF.sub.4. Further examples of NdXF compounds may include compounds in which X may be Mg and Ca or may be Mg, Ca and O; as well as other compounds containing NdF, including perovskite structures doped with neodymium. Certain NdXF compounds may advantageously enable broader absorption at wavelengths of about 580 nm. Since a neodymium oxyfluoride compound may comprise varying amounts of O and F (since neodymium oxyfluoride compounds are typically derived from varying amounts of neodymia Nd.sub.2O.sub.3 and neodymium fluoride NdF.sub.3), a neodymium oxyfluoride compound may have a selected refractive index that is between that of a NdO compound (for example, 1.8 for neodymia) and a NdF compound (for example, 1.60 for NdF.sub.3). Non-limiting examples of perovskite structure materials doped with neodymium can include those containing at least one constituent having a lower refractive index than the neodymium compound (e.g., NdF.sub.3), for example, metal fluorides of Na, K, Al, Mg, Li, Ca, Sr, Ba, and Y. Such host compounds may have lower refractive indices than NdF.sub.3 in the visible light spectrum, non-limiting examples of which may include NaF (n=1.32), KF (n=1.36), AlF.sub.3 (n=1.36), MgF.sub.2 (n=1.38), LiF (n=1.39), CaF.sub.2 (n=1.44), SrF.sub.2 (n=1.44), BaF.sub.2 (n=1.48), and YF.sub.3 (n=1.50) at a wavelength of 589 nm. As a result of doping with a high refractive index NdF compound, for example, NdF.sub.3, the resulting doped perovskite structure compound can have a refractive index that is between that of the host (for example, 1.38 for MgF.sub.2) and that of NdF.sub.3 (1.60). The refractive index of the NdF.sub.3-doped metal fluoride compound will depend on the ratio of Nd and metal ions.

(20) The refractive index of NdF.sub.3 is about 1.60. Therefore, it may sometimes be considered as providing a relative good RI match blend with silicone (which may have a refractive index around 1.51). An even better match may be obtained by mixing NdF.sub.3 with another material that may or may not comprise Nd. For example, NaNdF.sub.4 has an RI around 1.46. Thus, by proper blending of NdF.sub.3 with another material such as NaF or NaNdF.sub.4, the refractive index of the blend can be made to match that of silicone even better.

(21) FIG. 2 is a graph comparing absorption in a visible spectrum of neodymium fluoride dispersed in silicone represented by a curve 22, vs. that of standard neodymium glass (e.g., using Na.sub.2ONd.sub.2O.sub.3CaOMgOAl2O.sub.3K.sub.2OB.sub.2O.sub.3SiO.sub.2 as a composition for the Nd glass) represented by a curve 20 as a function of wavelength. It is significant that the respective materials share many of the same absorptive features, especially in the yellow (e.g., about 570 nm-about 590 nm) region. In use, one may encapsulate an LED chip/die with an encapsulant (e.g., silicone, epoxy, acrylic, or the like); the encapsulant may comprise a NdF or NdFO based material such as NdF.sub.3 in silicone deposited directly on the LED chip or on the array of LED chips (e.g., chip-on-board array, COB array) as further detailed herein.

(22) FIG. 3 is a graph comparing an emission spectrum of NdF.sub.3 blended into silicone and directly deposited on a commercial LED package (NICHIA 757), i.e., further encapsulating this LED package, as represented by a curve 32. As can be seen in FIG. 3, the spectrum is quite different, in that a significant depression is seen at a region or regions in the area between about 570 nm and about 590 nm, as compared to the emission spectrum of the base NICHIA757 LED, represented by a curve 30.

(23) FIG. 4 is a graph comparing an emission spectrum of NdF.sub.3 blended into silicone and directly deposited on a COB array (TG66) represented by a curve 42, to that of the base TG66 COB array represented by a curve 40 as a function of wavelength. The spectrum presented by the curve 42 is similar to the curve 32 of FIG. 3.

(24) The above examples evidence the utility of a NdF material (e.g., NdF.sub.3) as a color-filtering absorptive material, applied as part of an encapsulating material to LED packages or arrays, to enhance at least one of the following lighting metrics: CSI, CRI, R9, or whiteness index (i.e., proximity to the white body locus), or the like. Table 1 below shows resultant performances for examples presented in FIGS. 3 and 4 compared with a conventional LED comprising Nd glass.

(25) TABLE-US-00001 TABLE 1 Comparison of resultant performances presented in FIGS. 3 and 4 with a conventional LED with Nd:glass. L/W CCX CCY CCT CRI R9 GAI Revealness NdF.sub.3 on 236 0.4498 0.3954 2722 92 50 49 110 NICHIA 757 NdF.sub.3 on 249 0.4503 0.3934 2698 90 39 48 110 TG 66 White LED 249 0.4486 0.3961 2700 88 62 50 111 with Nd glass

(26) As can be seen above from Table 1, the NICHIA 757 LED device generally has a Lumens/Watt value of 236. When NdF.sub.3 is used as encapsulant in silicone, the CRI (color rendering/saturation index) is 92, the R9 (color rendering value of a red color chip) has a value of 60, the gamut area index (GAI) is 49, and the revealness based on LPI (as defined herein) of the emitted light is 110. When the TG 66 array of LED chips (COB array) is encapsulated in silicone comprising NdF.sub.3, the CRI is seen to be 90, the R9 value is 39, the GAI is 50, and Revealness is also 110. These values compare favorably to the color filtering effects of Nd glass combined with white LEDs, as shown on the bottom row of the Table 1. Values of chromaticity coordinates (CCX and CCY) and CCT (color correlated temperature) are shown for reference for all three cases.

(27) The NdF material does not have to be simply neodymium fluoride (NdF.sub.3) as in the example of FIGS. 3 and 4. It may also be any one of NdXF compounds with X representing other element or a combination of elements as described above, and being chemically attached with F. In this manner, such NdXF material may enhance at least one of the following lighting metrics: CSI, CRI, R.sub.9, whiteness index (i.e., proximity to the white body locus), or the like.

(28) For example, FIG. 5 is a graph comparing an emission spectrum of NdFO blended into silicone and directly deposited on a commercial LED package (NICHIA 757 with 4000 K CCT), thus further encapsulating this LED package, represented by a curve 52 as a function of wavelength. Similarly to the example of FIGS. 3 and 4, the spectrum 52 has a significant depression at a region or regions in the area between about 570 nm and about 590 nm, as compared to the emission spectrum of the base NICHIA757 LED represented by a curve 50.

(29) Table 2 below shows resultant performances for the example presented in FIG. 5 for NdFO in silicone directly deposited on a commercial LED package (NICHIA 757 with 4000K CCT) compared with a conventional LED with silicone encapsulant (NICHIA 757 with 4000K CCT) as well as with other types of silicone encapsulant doped with neodymia (Nd.sub.2O.sub.3) and with neodymium fluoride (NdF.sub.3). Table 2 lists similar parameter as Table 1 with an addition of CSI (color saturation index) parameter for the above materials.

(30) TABLE-US-00002 TABLE 2 The comparison of resultant performances for an LED with silicone encapsulant, doped with different Nd based materials, and without doping. Refractive index of encapsulant/ Lumens Revealness dopant output CCX CCY CCT CRI R.sub.9 CSI (LPI) Original 1.40 (RI for Si 1427 0.457 0.4073 2715 81 15 14 91 LED encapsulant (Nichia 757) per se) LED with 1.72 (for 1316 0.454 0.4096 2776 88 44 3 98 NdFO NdFO in Si doped encapsulant) silicone LED with 1.8 (for 1162 0.4551 0.4153 2804 86 57 4 94 Nd.sub.2O.sub.3 neodymia doped Nd.sub.2O.sub.3 in Si silicone encapsulant) LED with 1.6 (for NdF.sub.3 1420 0.4454 0.4053 2872 84 23 11 94 NdF.sub.3 in Si doped encapsulant) silicone

(31) It is noted that Nd.sub.2O.sub.3 will have a higher scattering loss than either NdFO or NdF.sub.3, due to its higher RI. However, NdFO has a better performance on the balance between CSI and LPI. Compared with Nd.sub.2O.sub.3, the NdF compound such as NdF.sub.3, either alone or mixed with the NdFO material, will have a lower RI to minimize scattering loss. Furthermore, as compared with Nd.sub.2O.sub.3, the NdF compound such as NdF.sub.3, either alone or mixed with an NdFO material, can enable a desirable yellow absorption peak for the spectrum of the LED light, to achieve a higher CSI with a reduced lumen penalty. Values of chromaticity coordinates (CCX and CCY), CCT and CRI are shown for reference, for all four cases.

(32) In certain embodiments, one may choose an NdF material or an NdFO material or an NdXF material, so as to have a refractive index match with the encapsulating material to minimize scattering loss. One may also blend one NdF material (e.g., neodymium fluoride) with another NdXF material (e.g., neodymium oxyfluoride). The element X in an NdXF compound may be chosen so as to tune the absorption in a region around 580 nm, in order to better match the spectrum with the R9 curve.

(33) In some embodiments, the NdF material (which broadly embraces all NdXF materials described herein), may be blended into an encapsulating material along with one or more luminescent materials, such as phosphors. For example, the NdF color-filtering material may be blended with a yellow-green phosphor and/or a red phosphor. For example, the NdF material may be blended with a Ce-doped YAG phosphor and/or a conventional red nitride phosphor, such as a Eu.sup.2+-doped CaAlSiN red phosphor. In another example, the NdFO material can be blended with YAG:Ce phosphor and a red nitride phosphor in silicone, encapsulating a blue-emitting NICHIA 757 LED. Without being limited by theory, emission from the YAG:Ce phosphor and the red nitride phosphor may be enhanced by the addition of the NdFO, in accordance with Mie scattering theory.

(34) FIGS. 6a-6d demonstrate different non-limiting examples of an LED-based lighting apparatus 60a, 60b, 60c and 60d respectfully, incorporating NdF compound (or more generally NdXF compounds as described herein) along with the phosphor to achieve favorable visible absorption/generation characteristics, according to various embodiments of the invention. In FIGS. 6a-6d the LED-based lighting apparatus 60a, 60b, 60c or 60d includes a dome 62 that can be an optically transparent or translucent substrate enclosing an LED chip 65 mounted on a printed circuit board (PCB) 66. Leads provide current to the LED chip 65, thus causing it to emit radiation. The LED chip may be any semiconductor light source, especially a blue or ultraviolet light source that is capable of producing white light when its emitted radiation is directed onto the phosphor. In particular, the semiconductor light source may be a blue/ultraviolet emitting LED based on a nitride compound semiconductor generalized as In.sub.iGa.sub.jAl.sub.kN (where 0i; 0j; 0k and i+j+k=1) having an emission wavelength greater than about 200 nm and less than about 550 nm. More particularly, the chip may be a near-UV or blue emitting LED having a peak emission wavelength from about 400 to about 500 nm. Even more particularly, the chip may be a blue emitting LED having a peak emission wavelength in a range about 440-460 nm. Such LED semiconductors are known in the art.

(35) According to one embodiment shown in FIG. 6a, a polymer composite layer (encapsulant compound) 64a can comprise a NdF compound (and/or generally NdXF compound) blended with a phosphor to impart favorable visible absorption/generation characteristics according to various embodiments described herein. This compound layer 64a can be disposed directly on a surface of the LED chip 65 and radiationally coupled to the chip. Radiationally coupled means that radiation from the LED chip is transmitted to the phosphor, and the phosphor emits radiation of a different wavelength. In a particular embodiment, the LED chip 65 may be a blue LED, and the polymer composite layer can include a blend of NdF and a yellow-green phosphor such as a cerium-doped yttrium aluminum garnet, Ce:YAG. The blue light emitted by the LED chip mixes with the yellow-green light emitted by the phosphors of polymer composite layer, and the net emission appears as white light which is filtered by the NdF. Thus LED chip 65 may be enclosed by the encapsulant material layer 64a. The encapsulant material may be a low-temperature glass, a thermoplastic or thermoset polymer or resin, or a silicone or epoxy resin. The LED chip 65 and the encapsulant material layer 64a may be encapsulated within a shell (restricted by the dome 62). Alternatively, the LED apparatus 60a may only include the encapsulant layer 64a without the outer shell/dome 62. In addition, scattering particles may be embedded in the encapsulant material. The scattering particles may be, for example, alumina (Al.sub.2O.sub.3), silica (SiO.sub.2) or titania (TiO.sub.2). The scattering particles can effectively scatter the directional light emitted from the LED chip, preferably with a negligible amount of absorption.

(36) To form a polymer composite layer that includes NdF(NdXF) on a surface of an LED chip, the particles may be dispersed in a polymer or polymer precursor, particularly a silicone or silicone epoxy resin, or precursors therefor. Such materials are well known for LED packaging. The dispersion mixture is coated on the chip by any suitable process, and particles having a larger density or particle size, or a larger density and larger particle size, preferentially settle in the region proximate the LED chip, forming a layer having a graded composition. Settling may occur during the coating or curing of the polymer or precursor, and may be facilitated by a centrifuging process, as known in the art. It is further noted that the parameters of dispersion of the phosphor and the NdF(NdXF), e.g., including particle density and size and process parameters, can be chosen to provide the phosphor material being closer to the LED chip 65 than NdF(NdXF) compounds, in order to provide an appropriate filtering by the NdF/NdXF compound of the light generated by the phosphor component.

(37) In an alternative exemplary embodiment shown in FIG. 6b, the phosphor layer 64b may be a conventionally fabricated encapsulant layer, and a separate encapsulant layer 68b with the NdF(NdXF) compound may be deposited on top of the phosphor layer 64b, e.g., using the appropriate conventional deposition/particle dispersion technique in a polymer or polymer precursor.

(38) In a further exemplary embodiment shown in FIG. 6c, a NdF/NdXF composite layer 68c can be coated on an outer surface of the dome (shell) 62. The performance of the coated layer 68b is similar to the performance of the encapsulant layer 68b with the NdF(NdXF) compound in FIG. 6b. Alternatively, the coating 68c in FIG. 6c can be deposited on an inner surface of the dome 62. More implementation details regarding coating of the dome/substrate will be discussed in reference to FIGS. 7-10. It is noted that the dome 62 itself can be transparent or translucent.

(39) In yet a further exemplary embodiment, as shown in FIG. 6d, the dome (shell) 62 can be used to deposit both NdF/NdXF composite layer/coating 68d on the outer surface of the dome 62 and a phosphor coating layer 64d on the inner surface of the dome 62. It is further noted that there may be different variations of this approach. For example, both coatings 64d and 68d may be deposited on one surface (outer or inner surface) of the dome 62 with the phosphor coating 64d being closer than the coating 68d to the LED chip 65. Also, coatings 64d and 68d (when deposited on one surface of the dome 62) can be combined in one layer similar to the encapsulant compound layer 64a in FIG. 6a. It is noted that the dome 62 itself can be transparent, translucent or transflective, in order to implement different variations of the example shown in FIG. 6d.

(40) Below are several non-limiting examples of an LED-based lighting apparatus using the coating containing the NdF and/or NdXF compound causing a desired color filter effect.

(41) FIG. 7 is an LED-based lighting apparatus suitable for area lighting applications in accordance with one embodiment of the invention. The LED-based lighting apparatus (which may also be referred to as a lighting unit or lamp) is an LED lamp 70 which may be configured to provide a nearly omnidirectional lighting capability. As shown in FIG. 7, the LED lamp 70 includes a bulb 72, a connector 74, and a base 76 between the bulb 72 and the connector 74, and a coating 78 on an outer surface of the bulb 72. The coating 78 includes the NdF and/or NdXF compound described herein. In other embodiments, the bulb 72 can be replaced by other transparent or translucent substrates. Alternatively, the coating 78 may be coated on an inner surface of the bulb 72 which can be transparent or translucent.

(42) FIG. 8 is an LED-based lighting apparatus 80 in accordance with a further embodiment of this invention. As shown in FIG. 8, the LED-based lighting apparatus is a ceiling lamp 80 (LED chip is not shown). The ceiling lamp 80 includes a hemispherical substrate 82 and a coating 88 containing the NdF and/or NdXF compound; the coating 88 is on an inner surface of the hemispherical substrate 82. Alternatively, the coating 88 may be coated on an outer surface of the hemispherical substrate 82 which can be transparent or translucent.

(43) FIG. 9 is an LED-based lighting apparatus in accordance with a further embodiment of this invention. As shown in FIG. 9, the LED-based lighting apparatus is a lens 90, and the lens 90 includes a substrate 92 (e.g., a flat substrate). In this embodiment, the substrate 92 includes NdF and/or NdXF compound coating (not shown) on an inner and/or outer surface thereof.

(44) FIG. 10 is an LED-based lighting apparatus 100 in accordance with one further embodiment of the invention. The LED-based lighting apparatus 100 includes a bulb (dome) 102, at least one LED chip 105 and a reflective substrate 106. The reflective substrate 106 is configured to reflect the visible light generated by the LED chip 105. In an embodiment described herein, the reflective substrate 106 includes NdF and/or NdXF compound coating (not shown) on an outer surface thereof for providing the desired filtering. In FIG. 10 the dome (102) can be constructed of a diffusing material, so that a certain amount of light from the LEDs will pass through, and a certain amount will be reflected back into the cavity (these amounts depend on how highly diffusing the dome material is). The reflected light will either reflect specularly or diffusely, depending on the diffusivity of the dome 102. These diffuse and/or specular reflections from the dome 102 will be incident upon the reflective substrate 106 coated according to one of the embodiment described herein. Alternatively the dome 102 can be constructed from a semi-reflective material to provide the same functionality.

(45) The coating materials described herein, including a compound containing Nd3+ ions and F ions, may have little optical scattering (diffusion) effect; or, alternatively, may cause considerable optical scattering on light passing therethrough. To increase a scattering angle, the coating may include discrete particles of an organic or inorganic material. Alternatively, the organic or inorganic material can be solely made up of discrete particles of the NdF and/or NdXF compound (e.g., formed partially or entirely of the NdF and/or NdXF compound) and/or made up of a mixture of discrete particles of the NdF and/or NdXF compound (e.g., formed partially or entirely of the NdF and/or NdXF compound) and particles formed of at least one other different material.

(46) In one embodiment, a suitable particle size for the organic or inorganic material can be from about 1 nm to about 10 microns. For the LED lamp 70 shown in FIG. 7, in order to maximize a scattering angle so that the LED lamp 70 could achieve omni-directional lighting, the particle size may be chosen to be much less than 300 nm to maximize efficiency of a Rayleigh scattering.

(47) Although not intended to be limiting, the NdF and/or NdXF compound coating may be applied by, for example, spray coating, roller coating, meniscus or dip coating, stamping, screening, dispensing, rolling, brushing, bonding, electrostatic coating or any other method that can provide a coating of even thickness. The following will describe three non-limiting examples of how to provide the NdF and/or NdXF compound coating on the substrate.

(48) In one embodiment, as shown in FIG. 7, the coating 37 may be coated on the bulb 72 by a bonding method. The LED lamp 70 can include a bonding layer (not shown) between the bulb 72 and the coating 78, and the bonding layer may include an organic adhesive or an inorganic adhesive. The organic adhesive can include an epoxy resin, an organic silicone adhesive, an acrylic resin, etc. The inorganic adhesive can include a silicate inorganic adhesive, a sulfate adhesive, a phosphate adhesive, an oxide adhesive, a boric acid salt adhesive etc.

(49) In another embodiment, as shown in FIG. 7, the coating 78 may be coated on the outer surface of the bulb 72 by a spray-coating method. Firstly, a liquid mixture containing, for example, NdFO and/or NdF.sub.3 compounds, silicone dioxide, dispersant such as Dispex A40, water and optionally TiO.sub.2 or Al.sub.2O.sub.3 is formed. Subsequently, the formed liquid mixture is sprayed onto the bulb 72. Finally, the bulb 72 is cured to obtain the coated LED lamp 70.

(50) In one embodiment, as shown in FIG. 7, the coating 78 may be coated onto the outer surface of the bulb 72 by an electrostatic coating method. Firstly, electrically charged powder consisting, for example, NdFO and/or NdF.sub.3 compounds, SiO.sub.2 and Al.sub.2O.sub.3 is produced. Subsequently, the powder is coated onto the bulb 72 which is oppositely charged.

(51) In other embodiments of the invention, both the spray coating method and the electrostatic coating method may use materials without organic solvent or organic compound, which can extend the service life of the LED light apparatus and avoid the discoloration typically caused by sulfonation.

(52) In a further embodiment, a weight percentage of NdF.sub.3 or another Nd.sup.3+ ion source (for examples, using NdF compounds and NdXF compounds) in the coating may be between 1% to about 20%. In one specific embodiment, the weight percentage of NdF.sub.3 or another Nd.sup.3+ ion source in the coating may be in a range from about 1% to about 10%. In other embodiments, to promote refraction of the light to achieve a white reflective appearance, the coating further may include an additive having a higher refractive index relative to the NdF and/or NdXF compound. The additive can be selected from metal oxides and non-metal oxides, such as TiO.sub.2, SiO.sub.2 and Al.sub.2O.sub.3.

(53) Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one having ordinary skill in the art to which this disclosure belongs. The terms first, second, and the like, as used herein, do not denote any order, quantity, or importance, but rather are employed to distinguish one element from another. Also, the terms a and an do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The use of including, comprising or having and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof, as well as additional items. The terms connected and coupled are not restricted to physical or mechanical connections or couplings, and can include electrical and optical connections or couplings, whether direct or indirect.

(54) Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. The various features described, as well as other known equivalents for each feature, can be mixed and matched by one of ordinary skill in this art, to construct additional systems and techniques in accordance with principles of this disclosure.

(55) In describing alternate embodiments of the apparatus claimed, specific terminology is employed for the sake of clarity. The invention, however, is not intended to be limited to the specific terminology so selected. Thus, it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish similar functions.

(56) It is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention, which is defined by the scope of the appended claims. Other embodiments are within the scope of the following claims.

(57) It is noted that various non-limiting embodiments described and claimed herein may be used separately, combined or selectively combined for specific applications.

(58) Further, some of the various features of the above non-limiting embodiments may be used to advantage, without the corresponding use of other described features. The foregoing description should therefore be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.