Red-deficiency-compensating phosphor LED
First Claim
1. A light emitting device comprising:
- light-generating means for emitting first light having a first peak wavelength in a first spectral range in response to an applied excitation signal;
wavelength-conversion means optically coupled to said light-generating means to receive said first light for converting a portion of said first light to form composite light having a broadband spectral distribution, said wavelength-conversion means including a primary fluorescent material that converts said first light into second light having a second peak wavelength in a second spectral range, said wavelength-conversion means including a supplementary fluorescent material that converts said first light into third light having a third peak wavelength in a red spectral range of a visible light spectrum, said composite light being at least partially formed by said first light, said second light and said third light such that said broadband spectral distribution includes said first spectral range, said second spectral range and said red spectral range; and
means in optical communication with said light-generating means and said wavelength-conversion means for directing said first light, said second light and said third light in a predetermined direction.
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Abstract
A light emitting device and a method of fabricating the device utilize a supplementary fluorescent material that radiates secondary light in the red spectral region of the visible light spectrum to increase the red color component of the composite output light. The secondary light from the supplementary fluorescent material allows the device to produce “white” output light that is well-balanced with respect to color for true color rendering applications. The supplementary fluorescent material is included in a fluorescent layer that is positioned between a die and a lens of the device. The die is preferably a GaN based die that emits light having a peak wavelength of 470 nm. The fluorescent layer also includes a main fluorescent material. Preferably, the main fluorescent material is Cerium (Ce) activated and Gadolinium (Gd) doped Yttrium Aluminum Garnet (YAG) phosphor (“Ce:YAG phosphor”). In a first preferred embodiment, the supplementary fluorescent material is a compound that is produced by doping the Ce:YAG phosphor with a trivalent ion of Praseodymium (Pr). In a second preferred embodiment, the supplementary fluorescent material is Europium (Eu) activated Strontium Sulphide (SrS) phosphor. The amount of supplementary phosphor in the fluorescent layer can vary depending on the amount of red color that may be required in the white output light. The exact amount of supplementary phosphor is not critical to the invention.
392 Citations
18 Claims
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1. A light emitting device comprising:
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light-generating means for emitting first light having a first peak wavelength in a first spectral range in response to an applied excitation signal;
wavelength-conversion means optically coupled to said light-generating means to receive said first light for converting a portion of said first light to form composite light having a broadband spectral distribution, said wavelength-conversion means including a primary fluorescent material that converts said first light into second light having a second peak wavelength in a second spectral range, said wavelength-conversion means including a supplementary fluorescent material that converts said first light into third light having a third peak wavelength in a red spectral range of a visible light spectrum, said composite light being at least partially formed by said first light, said second light and said third light such that said broadband spectral distribution includes said first spectral range, said second spectral range and said red spectral range; and
means in optical communication with said light-generating means and said wavelength-conversion means for directing said first light, said second light and said third light in a predetermined direction. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of fabricating a light emitting device comprising steps of:
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providing a light source that emits first light having a first peak wavelength;
preparing a phosphor-epoxy mixture, said phosphor-epoxy mixture including a primary fluorescent material that emits second light having a second peak wavelength in response to exposure to said first light and a supplementary fluorescent material that emits third light having a third peak wavelength in a red spectral region of a visible light spectrum, said supplementary fluorescent material being responsive to exposure to said first light;
depositing said phosphor-epoxy mixture over said light source to form a fluorescent layer that at least partially encapsulates said light source; and
depositing a transparent material over said fluorescent layer to form a lens above said fluorescent layer. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A light emitting device comprising:
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a light source that emits first light having a first peak wavelength in a first spectral range in response to an applied electrical signal;
a fluorescent layer positioned over said light source to receive said first light emitted from said light source, said fluorescent layer including a first fluorescent material having a property of radiating second light having a second peak wavelength in a second spectral range in response to said first light, said fluorescent layer including a second fluorescent material having a property of radiating third light having a third peak wavelength in a red spectral range of a visible light spectrum;
a light-propagation medium optically coupled to said fluorescent layer to transmit said first light, said second light and said third light as composite output light in a direction away from said light source, said composite output light having a color characteristic at least partially determined by intensities of said first light, said second light and said third light. - View Dependent Claims (15, 16, 17, 18)
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Specification
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- Resources
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Current AssigneeLumileds LLC (Apollo Global Management, Inc.)
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Original AssigneeLumileds Lighting US LLC (Apollo Global Management, Inc.)
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InventorsMueller, Gerd, Mueller, Regina, Lowery, Christopher H.
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Primary Examiner(s)Day, Michael H.
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Assistant Examiner(s)WILLIAMS, JOSEPH L
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Application NumberUS09/252,207Time in Patent Office1,104 DaysField of Search313/501, 313/512, 313/503, 313/504, 313/506, 313/509, 313/489, 313/486, 313/467, 257/98, 257/99, 257/100US Class Current313/512CPC Class CodesH01L 33/504 Elements with two or more w...
