Classifications

• • 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
  • H10H20/85—Packages
  • H10H20/851—Wavelength conversion means
  • H10H20/8511—Wavelength conversion means characterised by their material, e.g. binder
  • H10H20/8512—Wavelength conversion materials
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
  • F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
  • F21K9/60—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
  • F21K9/64—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W90/00—Package configurations
• • 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
  • H10H20/81—Bodies
  • H10H20/811—Bodies having quantum effect structures or superlattices, e.g. tunnel junctions
  • H10H20/812—Bodies having quantum effect structures or superlattices, e.g. tunnel junctions within the light-emitting regions, e.g. having quantum confinement structures
• • 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
  • H10H20/81—Bodies
  • H10H20/813—Bodies having a plurality of light-emitting regions, e.g. multi-junction LEDs or light-emitting devices having photoluminescent regions within the bodies
• • 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
  • H10H20/81—Bodies
  • H10H20/822—Materials of the light-emitting regions
  • H10H20/824—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP
  • H10H20/825—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP containing nitrogen, e.g. GaN
• • 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
  • H10H20/85—Packages
  • H10H20/851—Wavelength conversion means
  • H10H20/8515—Wavelength conversion means not being in contact with the bodies
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N5/00—Radiation therapy
  • A61N5/06—Radiation therapy using light
  • A61N5/0613—Apparatus adapted for a specific treatment
  • A61N5/0618—Psychological treatment
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
  • F21Y2115/00—Light-generating elements of semiconductor light sources
  • F21Y2115/10—Light-emitting diodes [LED]
• • 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
  • H10H20/85—Packages
  • H10H20/851—Wavelength conversion means
  • H10H20/8511—Wavelength conversion means characterised by their material, e.g. binder
  • H10H20/8512—Wavelength conversion materials
  • H10H20/8513—Wavelength conversion materials having two or more wavelength conversion materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H29/00—Integrated devices, or assemblies of multiple devices, comprising at least one light-emitting semiconductor element covered by group H10H20/00
  • H10H29/20—Assemblies of multiple devices comprising at least one light-emitting semiconductor device covered by group H10H20/00
  • H10H29/24—Assemblies of multiple devices comprising at least one light-emitting semiconductor device covered by group H10H20/00 comprising multiple light-emitting semiconductor devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H29/00—Integrated devices, or assemblies of multiple devices, comprising at least one light-emitting semiconductor element covered by group H10H20/00
  • H10H29/80—Constructional details
  • H10H29/85—Packages
  • H10H29/851—Wavelength conversion means
  • H10H29/8511—Wavelength conversion means characterised by their material, e.g. binder
  • H10H29/8512—Wavelength conversion materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H29/00—Integrated devices, or assemblies of multiple devices, comprising at least one light-emitting semiconductor element covered by group H10H20/00
  • H10H29/80—Constructional details
  • H10H29/85—Packages
  • H10H29/851—Wavelength conversion means
  • H10H29/8511—Wavelength conversion means characterised by their material, e.g. binder
  • H10H29/8512—Wavelength conversion materials
  • H10H29/8513—Wavelength conversion materials having two or more wavelength conversion materials

Definitions

• Embodiments of the present invention are directed to full solid-state spectrum white light emitting devices comprising photoluminescence wavelength conversion materials. More particularly, although not exclusively, embodiments concern full spectrum white light emitting devices for generating full spectrum white light having a spectrum from blue light to red light that closely resembles natural sunlight. BACKGROUND OF THE INVENTION
• White light emitting LEDs include one or more photoluminescence materials (typically inorganic phosphor materials), which absorb a portion of the blue light emitted by the LED (solid-state excitation source) and re-emit visible light of a different color (wavelength). The portion of the blue light generated by the LED that is not absorbed by the phosphor material combined with the light emitted by the phosphor provides light which appears to the eye as being white in color. Due to their long operating life expectancy (>50,000 hours) and high efficacy (100 lumens per watt and higher), white LEDs have rapidly replaced conventional fluorescent, compact fluorescent and incandescent lamps.
• photoluminescence materials typically inorganic phosphor materials
• CCT Correlated Color Temperature
• CIE International Commission on Illumination
• CRI General Color Rendering Index
• the CCT of a lighting source is measured in kelvin (K) and is the color temperature of a Plankian (black-body) radiator that radiates light of a color that corresponds to the color of the light generated by the lighting source.
• K kelvin
• the General CRI Ra characterizes how faithfully a lighting source renders the true colors of an object and is based on a measure of how well a light source’s illumination of eight color test samples (R1 to R8) compares with the illumination provided by a reference source. In general, the higher the value indicates its closeness to a black radiator and natural sunlight.
• General CRI Ra can take negative values and has a maximum value of 100.
• the General CRI Ra gave a useful measure of subtle differences in light output of incandescent sources which generate a full spectrum that closely resembles sunlight.
• the General CRI Ra can prove to be inadequate as it is an average measure of color rendition over a limited range of colors and gives no information of the lighting source’s performance for particular colors or highly saturated colors.
• the CRI color samples R9 to R12 saturated colors“Saturated Red”,“Saturated Yellow”,“Saturated Green”,“Saturated Blue”
• R13 to R15 Light Skin Tone”,“Leaf Green”,“Medium Skin Tone”
• blue light has a greater tendency than other colors to affect living organisms through the disruption of their biological processes which rely upon natural cycles (circadian) of daylight and darkness. It is believed that exposure to blue light late in the evening and at night can be detrimental to health.
• CAF and MR are the ratio of the circadian luminous efficacy of radiation (CER) to luminous efficacy of radiation (LER) and each provide a measure of the brain’s sensitivity to light; that is, a measure of human non-visual sensitivity to light.
• CER circadian luminous efficacy of radiation
• LER luminous efficacy of radiation
• CAF is based on studies that measure human melatonin levels before and after exposure to specific wavelengths of light to establish a Circadian Action Spectrum (CAS) or circadian sensitivity spectrum c(l).
• CAF is the ratio of the circadian efficacy to luminous efficacy of radiation.
• MR is based on the absorption spectrum of the melanopsin photopigment found in mammalian ipRGCs (intrinsically photosensitive Retinal Ganglion Cells) to establish a melanopic response (sensitivity) spectrum m(l).
• MR is the ratio of the circadian efficacy to luminous efficacy of radiation.
• EML Equivalent Melanopic Lux
• the present invention arose in an endeavor to overcome at least in part the shortcomings of known solid-state white light emitting devices and provide human centric full spectrum white light emitting devices with an efficacy at least approaching or exceeding that of current CRI80 devices.
• the invention concerns full spectrum white light emitting devices for generating full spectrum white light having a spectral content from blue wavelengths to red wavelengths that resembles natural sunlight as closely as possible.
• At least some embodiments of the invention are directed to white light emitting devices for generating white light that closely resembles natural light in the blue to cyan wavelength region of the spectrum.
• such white light emitting devices generate full spectrum white light that closely resembles natural light in the blue to cyan wavelength region (430 nm to 520 nm) where human non-visual perception measured by Circadian Action Factor (CAF) and Melanopic Response (MR) is affected most.
• CAF Circadian Action Factor
• MR Melanopic Response
• Full spectrum white light emitting devices in accordance with the invention utilize broadband solid-state excitation sources, for example blue LEDs, which generate broadband excitation light with a dominant wavelength from about 420 nm to about 480 nm (that is in the blue wavelength region of the visible spectrum).
• broadband solid-state excitation sources for example blue LEDs, which generate broadband excitation light with a dominant wavelength from about 420 nm to about 480 nm (that is in the blue wavelength region of the visible spectrum).
• “broadband” is used to denote light that has a FWHM (Full Width at Half Maximum) of at least 25 nm.
• the FWHM may be at least 30 nm or at least 50 nm and may have a FWHM from about 25 nm to about 70 nm; optionally may have a FWHM in a range from about 30 nm to about 70 nm.
• Broadband may also be used to denote blue light that is composed of a combination of at least two different wavelength blue light emissions in a wavelength range from about 420 nm to about 480 nm.
• Use of broadband blue excitation light enables the light emitting device to generate full spectrum light that closely resembles natural light in the blue to cyan (430 nm to 520 nm) wavelength region of the spectrum.
• Embodiments of the invention further concern full spectrum white light emitting devices that generate white light having a light intensity at wavelengths corresponding to the red wavelength region of the spectrum that has been optimized (reduced) to improve efficacy.
• the device comprises an orange to red photoluminescence material whose peak emission wavelength/FWHM is selected to reduce light intensity (photon count) at wavelengths corresponding the red wavelength region (range) of the spectrum, in particular reducing light intensity for wavelengths longer than about 650 nm which can affect the values of CRI R9 (“Saturated Red”) and CRI R8 (“Reddish Purple”), at which wavelengths the photopic response of the eye (i.e. photopic luminosity function) is generally low (about 0.1).
• CRI R9 saturated Red
• CRI R8 Reddish Purple
• a full spectrum white light emitting device comprising: photoluminescence materials for generating light with a peak emission wavelength from about 490 nm to about 680 nm; and a broadband solid-state excitation source for generating broadband excitation light with a dominant wavelength from about 420 nm to about 480 nm, wherein the device generates white light having a spectrum whose intensity decreases from its maximum value in the orange to red wavelength region of the spectrum to about 50% of said maximum value at a wavelength from about 645 nm to about 695 nm, and wherein, over a wavelength range from about 430 nm to about 520 nm, a maximum percentage intensity deviation of said white light from the intensity of light of a black-body curve or CIE Standard Illuminant D of the same Correlated Color Temperature is less than 60%.
• the maximum intensity in the orange to red region of the spectrum corresponds to photoluminescence converted (generated) light and the maximum intensity occurs at a wavelength longer than about 570 nm.
• the maximum intensity may occur at wavelength ranging from about 590 nm to about 620 nm.
• said maximum percentage intensity deviation of light emitted by the device is less than at least one of 50%, 40%, 30%, 20% and 10%.
• the white light may have a Circadian Action Factor (CAF) that is within 5% of the CAF of the black-body curve or CIE Standard Illuminant D.
• CAF Circadian Action Factor
• white light generated by the device has a CRI R9 and/or a CRI R8 that is less than 90.
• the white light has a spectrum whose intensity decreases from its maximum value in the orange to red wavelength region to about 50% of said maximum value at a wavelength that is from about 645 nm to about 665 nm, and has a CRI Ra of at least 80.
• the white light may have a spectrum whose intensity decreases from its maximum value to about 50% of said maximum value of light emitted by the device at a wavelength that is from about 665 nm to about 690 nm, and has a CRI Ra of at least 90 and CRI R9 greater than 50.
• the white light may have a spectrum whose intensity decreases from its maximum value to about 50% of said maximum value of light emitted by the device at a wavelength from about 680 nm to about 695 nm, and has a CRI Ra of at least 95 and a CRI R9 greater than 60.
• the photoluminescence materials comprise at least one or a combination of photoluminescence materials which generates light with a peak emission wavelength from about 620 nm to about 655 nm.
• the white light may have a Correlated Color Temperature from about 2700K to about 3000 K and the device may have an efficacy of at least 102 lm/W.
• the white light may have a Correlated Color Temperature from about 4000K to about 6800 K and the device may have an efficacy of at least 110 lm/W.
• the broadband solid-state excitation source generates broadband excitation light with a FWHM of at least 25 nm.
• the broadband excitation light may comprise a combination of blue light emissions of two or more different wavelengths.
• the different wavelength blue light emissions can be generated in two ways: (i) using multiple individual blue LEDs (narrowband LEDs) of different dominant wavelengths or (ii) individual LEDs (broadband LEDs) that generate multiple blue wavelength emissions using, for example, specially designed multiple different quantum wells in the active region.
• a broadband solid-state excitation source can be constituted by one or more narrowband solid-state light sources; such as for example, LEDs or laser diodes, each of which“directly” generates narrowband blue light of different dominant wavelengths from 420 nm to 480 nm.
• the broadband solid-state excitation source may comprise: a first solid-state light source for generating a blue light emission with a first dominant wavelength from 420 nm to 480 nm; and a second solid-state light source for generating a different blue light emission with a second dominant wavelength from 420 nm to 480 nm.
• the first dominant wavelength can be from 420 nm to 450 nm; and the second dominant wavelength can be from 450 nm to 480 nm.
• the broadband blue excitation source may further comprise a third solid-state light source for generating a blue light emission with a third dominant wavelength from 420 nm to 480 nm which is different from the first and second dominant wavelengths.
• a broadband solid-state excitation source also encompasses a broadband solid-state light source; for example, a broadband blue LED such as an InGaN/GaN blue LED having an active region that directly generates blue light emissions of multiple different wavelengths using different quantum wells in a multiple-quantum-well (MQW) structure.
• a broadband blue LED such as an InGaN/GaN blue LED having an active region that directly generates blue light emissions of multiple different wavelengths using different quantum wells in a multiple-quantum-well (MQW) structure.
• the broadband solid-state excitation source comprises an LED having at least two different quantum wells that each generate a blue light emission with a respective different dominant wavelength.
• Broadband solid-state excitation sources of the invention are to be contrasted with known white LEDs that utilize narrowband blue LEDs that generate blue light of a single narrowband wavelength having a FWHM in a range 15 nm to 20 nm.
• Broadband blue solid-state excitation sources of the invention are to be further contrasted with known white LEDs that utilize UV solid-state light sources (UV LEDs) in which the blue excitation light is generated indirectly through a process of photoluminescence conversion of UV light using a blue light emitting (420 nm to 480 nm) photoluminescence material (phosphor).
• UV LEDs UV solid-state light sources
• broadband solid-state excitation sources/white light emitting devices in accordance with the invention do not utilize/include a photoluminescence material to generate excitation light in a range 420 nm to 480 nm.
• the photoluminescence materials can comprise: a first photoluminescence material with a peak emission wavelength from 490 nm to 550 nm and a second photoluminescence material with a peak emission wavelength from 600 nm to 680 nm.
• the present invention encompasses a full spectrum white light emitting device comprising: photoluminescence materials for generating light with a peak emission wavelength from about 490 nm to about 680 nm; and a broadband solid-state excitation source for generating broadband excitation light with a dominant wavelength from about 420 nm to about 480 nm, wherein the device generates white light with a Correlated Color Temperature from about 1800K to about 6800K and wherein the white light has a spectrum that has a CAF that is within 5% of the CAF of a black-body curve or CIE Standard Illuminant D of the same Correlated Color Temperature.
• said maximum percentage intensity deviation of said light is less is than at least one of 50%, 40%, 30%, 20% and 10%.
• the white light may have a spectrum whose intensity drops to half its maximum intensity at a wavelength from about 645 nm to about 695 nm.
• the white light may have a CRI R9 less than 90.
• the white light has a Correlated Color Temperature from about 2700K to about 3000 K and the device has an efficacy of at least 102 lm/W, or the white light has a Correlated Color Temperature from about 4000K to about 6800 K and the device has an efficacy of at least 110 lm/W.
• Embodiments of the invention find utility in a packaged white light emitting devices where the photoluminescence materials (e.g. yellow to green and orange to red photoluminescence materials) are packaged with the broadband solid-state excitation source such as surface mountable device, chip on board, and filament.
• the photoluminescence materials can be located remote to the broadband solid-state excitation source.
• FIGS. 1a and 1b show a remote phosphor full spectrum white light emitting device, according to some embodiments
• FIG.2a is a schematic of a broadband blue solid-state excitation source in accordance with an embodiment of the invention for use in the full spectrum white light emitting device of FIGS.1a and 1b;
• FIG.2b is a schematic of a broadband blue solid-state excitation source in accordance with an another embodiment of the invention for use in the full spectrum white light emitting device of FIGS.1a and 1b;
• FIG. 3a is a schematic cross-sectional view of a full spectrum white light emitting device, according to some embodiments.
• FIG. 3b is a schematic cross-sectional view of a full spectrum white light emitting device, according to some embodiments.
• FIGS. 4a and 4b is a schematic of a full spectrum white light emitting device, according to some embodiments.
• FIG. 5 shows: (A) intensity spectra, normalized intensity I versus wavelength (nm), for: (i) a known full spectrum light emitting device that utilizes a narrowband excitation source - spectrum denoted A (dotted line), (ii) a full spectrum light emitting device in accordance with the invention that utilizes a broadband excitation source - spectrum denoted B (thin solid line (iii) black-body curve (bbc) (dashed line) for a CCT that is nominally the same as that of spectra A and B; and (B) Circadian Action Spectrum (CAS)– thick solid line, Relative Quantum Sensitivity versus wavelength (nm);
• FIG.10 is a side view of an LED-filament lamp according to some embodiments.
• FIGS. 11a and 11b are schematic cross-sectional B-B side and partial cutaway plan views of an LED-filament white light emitting device according to some embodiments for use in the lamp of FIG.10. DETAILED DESCRIPTION OF THE INVENTION
• Embodiments of the invention concern white light emitting devices that comprise a broadband solid-state excitation source, for example one or more LEDs, that is operable to generate broadband blue excitation light with a dominant wavelength from 420 nm to 480 nm.
• a broadband solid-state excitation source for example one or more LEDs
• “broadband” is used to denote light that has a FWHM (Full Width at Half Maximum) of at least 25 nm.
• the FWHM may be at least 30 nm or at least 50 nm and may have a FWHM in a range from 25 nm to 70 nm; optionally may have a FWHM in a range from 30 nm to 70 nm.
• Broadband may also be used to denote blue light that is composed of a combination of at least two different wavelength blue light emissions in a wavelength range from 420 nm to 480 nm. More particularly, although not exclusively, embodiments of the invention concern white light emitting devices for generating full spectrum white light that closely resembles natural light in the blue to cyan wavelength region of the visible spectrum (about 430 nm to about 520 nm). [0058] Remote phosphor full spectrum white light emitting devices
• FIGS. 1a and 1b illustrate a remote phosphor solid-state full spectrum white light emitting device according to an embodiment of the invention in which FIG.1a is a partial cross- sectional plan view and FIG. 1b is a sectional view through A-A.
• the device 110 is configured to generate full spectrum white light with a CCT (Correlated Color Temperature) from 1800K and 6800K.
• CCT Correlated Color Temperature
• the device can be used alone or comprise a part of a downlight or other lighting arrangement.
• the device 110 comprises a hollow cylindrical body 112 composed of a circular disc-shaped base 114, a hollow cylindrical wall portion 116 and a detachable annular top 118.
• the base 114 is preferably fabricated from aluminum, an alloy of aluminum or any material with a high thermal conductivity.
• the base 114 can be attached to the wall portion 116 by screws or bolts or by other fasteners or by means of an adhesive.
• the device 110 further comprises a plurality (five in the example of FIGS. 1a and 1b) of broadband blue solid-state excitation sources 120 that are mounted in thermal communication with a circular-shaped MCPCB (metal core printed circuit board) 122.
• MCPCB metal core printed circuit board
• FIGS. 2a to 4b Various embodiments of the broadband blue solid-state excitation sources 120 are illustrated in FIGS. 2a to 4b.
• the device 10 can further comprise light reflective surfaces 124 and 126 that respectively cover the face of the MCPCB 122 and the inner curved surface of the cylindrical wall 116.
• the device 110 further comprises a photoluminescence wavelength conversion component 128 that is located remotely to the excitation sources 120 and operable to absorb a portion of the excitation light generated by the excitation sources 120 and convert it to light of a different wavelength by a process of photoluminescence.
• the emission product of the device 110 comprises the combined light generated by the broadband blue excitation sources 120 and photoluminescence light generated by the photoluminescence wavelength conversion component 128.
• the photoluminescence wavelength conversion component may be formed of a light transmissive material (for example, polycarbonate, acrylic material, silicone material, etc.) that incorporates a mixture of a yellow, red and/or green phosphor.
• the photoluminescence wavelength conversion component may be formed of a light transmissive substrate that is coated with phosphor material(s).
• the wavelength conversion component 128 is positioned remotely to the excitation sources 120 and is spatially separated from the excitation sources.
• “remotely” and“remote” means in a spaced or separated relationship.
• wavelength conversion component and excitation sources are separated by an air, while in other embodiments they can be separated by a suitable light transmissive medium, such as for example a light transmissive silicone or epoxy material.
• the wavelength conversion component 128 is configured to completely cover the housing opening such that all light emitted by the lamp passes through the wavelength component 128. As shown, the wavelength conversion component 128 can be detachably mounted to the top of the wall portion 116 using the top 118 enabling the component and emission color of the lamp to be readily changed.
• FIG. 2a is a schematic representation of a broadband blue solid-state excitation source 220, according to an embodiment of the invention.
• the broadband blue solid-state excitation source 220 is configured to generate broadband blue excitation light with a dominant wavelength from 420 nm to 470 nm, that is, in the blue wavelength region of the visible spectrum. In this embodiment, it also has a FWHM from 25 nm to 50 nm.
• the broadband blue solid-state excitation source 220 can comprise a first solid-state light source 230 and a second solid-state light source 232, which in this example are narrowband blue LED chips (e.g. blue-emitting GaN -based LED chips).
• the first solid-state light source 230 generates a blue light emission having a first dominant wavelength l d1 from 420 nm to 470 nm and the second solid-state light source 232 generates a blue light emission having a second dominant wavelength ld2 from 420 nm to 470 nm.
• the first and second solid-state light sources are selected such that the dominant wavelengths of light generated by the sources are different (i.e. l d1 is different to l d2 ).
• the combination of light from the first and second solid-state light sources 230/232 constitutes the broadband blue excitation light output 242 of the broadband blue solid-state excitation source 220 and has a dominant wavelength from 420 nm to 470 nm and has a FWHM from 25 nm to 50 nm.
• the solid-state excitation source may comprise a single solid-state light source.
• a single solid-state light source is defined as one or more solid-state light sources each of which generates light with the same (i.e. single/solitary) dominant wavelength and with a FWHM of at least 25nm.
• the broadband blue solid-state excitation source 220 can comprise a surface mountable device (SMD), such as for example an SMD 2835 LED package, in which the first and second solid-state light sources are flip-chip bonded on a top face of a substrate 234. Electrical contacts 236, 238 can be provided on the bottom face of the substrate 234 for operating the excitation source.
• the first and second solid-state light sources 230, 232 can be encapsulated with a light transmissive optical encapsulant 240, such as for example a silicone or epoxy material.
• FIG. 2b is a schematic representation of a broadband blue solid-state excitation source 220, according to an embodiment of the invention.
• the solid-state excitation source 220 is configured to generate excitation light with a dominant wavelength from 420 nm to 470 nm, that is, in the blue wavelength region of the visible spectrum. In this embodiment, it also has a FWHM from 25 nm to 50 nm.
• the solid- state excitation source 220 comprises a broadband solid-state light source 241, which in this example is a single broadband LED such as for example an InGaN/GaN blue LED having an active region with multiple-quantum-wells (MQWs), as disclosed in Appl. Phys. lett.
• MQWs multiple-quantum-wells
• the broadband solid-state light source 241 generates broadband blue light comprising multiple overlapping blue light emissions of peak wavelengths from 420 nm to 470 nm.
• the single solid-state light source 241 generates light with a single/solitary dominant wavelength and with a FWHM of at least 25nm.
• the solid-state excitation source 220 can comprise a surface mountable device (SMD), such as for example an SMD 2835 LED package, in which the solid- state light source is flip-chip bonded on a top face of a substrate 234. Electrical contacts 236, 238 can be provided on the bottom face of the substrate 234 for operating the excitation source.
• the solid-state light source 241 can be encapsulated with a light transmissive optical encapsulant 240, such as for example a silicone or epoxy material.
• a light transmissive optical encapsulant 240 such as for example a silicone or epoxy material.
• FIG. 3a is a schematic cross-sectional representation of a packaged full spectrum white light emitting device 310a, according to an embodiment of the invention.
• the device 310a is configured to generate full spectrum white light with a CCT (Correlated Color Temperature) from 1800 K to 6800K.
• CCT Correlated Color Temperature
• the device 310a comprises a broadband blue solid-state excitation source constituted by first and second solid-state light sources 330, 332, for example blue-emitting GaN (gallium nitride)-based LED chips, that are housed within a package 344.
• the first solid-state light source 330 can generate a blue light emission having a first dominant wavelength l d1 from 420 nm to 470 nm and the second solid-state light source 332 can generate a blue light emission having a second dominant wavelength ld2 from 420 nm to 470 nm.
• the dominant wavelength ld1 of the first solid-state light source is different from the dominant wavelength l d2 of the second solid-state light source.
• the package which can for example comprise Surface Mountable Device (SMD) such as an SMD 2835 LED package, comprising upper portion 346 and base portion 348.
• the upper body part 346 defines a recess 350 which is configured to receive the solid-state light sources 330, 332.
• the package 344 can further comprise electrical connectors 352 and 354 on an exterior face of the base of the package 344.
• the electrical connectors 352, 354 can be electrically connected to electrode contact pads 356, 358 and 360 on the floor of the recess 350.
• the solid-state light sources (LED chips) 330, 332 can be mounted to a thermally conductive pad 362 located on the floor of the recess 350.
• the LED chip’s electrode pads can be electrically connected to corresponding electrode contact pads 356, 358 and 360 on the floor of the package 344 using bond wires 362.
• the LED chips can be flip-chip mounted in and electrically connected to the package.
• the recess 350 is filled with a light transmissive optical encapsulant 364, typically an optically clear silicone, which is loaded with a mixture of photoluminescence materials such that the exposed surfaces of the LED chips 330, 332 are covered by the photoluminescence/silicone material mixture.
• the walls of the recess 350 can be inclined and have a light reflective surface.
• the one or more solid-state light sources each generate light with the same (i.e. single/solitary) dominant wavelength and with a FWHM of at least 25nm.
• FIG. 3b is another embodiment of the present invention. It is similar to FIG. 3a except that the first and second narrowband solid-state light sources are replaced by two broadband blue LEDs 341a/341b having an active region with multiple-quantum-wells. Typically, the first and second broadband blue solid-state light sources 341a/341b each generate broadband blue excitation light having dominant wavelengths ld which are the same.
• FIGS. 4a and 4b illustrate a Chip On Board (COB) packaged full spectrum white light emitting device 410 according to an embodiment of the invention in which FIG.4a is a plan view and FIG.4b is a sectional view through B-B.
• the device 410 can be configured to generate warm white light with a CCT (Correlated Color Temperature) from 2500K to 5000K and a CRI (Color Rendering Index) of greater than 95.
• CCT Chip On Board
• the device 410 comprises a plurality (twelve in the example of FIG. 4a) broadband blue solid-state excitation sources 420, for example broadband blue-emitting GaN (gallium nitride)-based LED flip-chip dies, mounted in thermal communication with a square-shaped MCPCB 468.
• broadband blue solid-state excitation sources 420 for example broadband blue-emitting GaN (gallium nitride)-based LED flip-chip dies, mounted in thermal communication with a square-shaped MCPCB 468.
• the excitation sources 420 can be configured as a generally circular array.
• the solid-state excitation sources (broad-band LED dies) 420 can each generate excitation light having a dominant wavelength l d from 440 nm to 455 nm. In this embodiment, they have a FWHM (Full Width Half Maximum) from 25 nm to 50 nm.
• Electrical contacts 472, 474 can be provided on the top face of the MCPCB 468 for operating the white light emitting device 410.
• the broad-band LED flip-chip dies 420 are encapsulated with a light transmissive optical encapsulant 466, such as for example a silicone or epoxy material, which is loaded with a mixture of photoluminescence materials such that the exposed surfaces of the LED dies 420 are covered by the photoluminescence/silicone material mixture.
• a light transmissive optical encapsulant 466 such as for example a silicone or epoxy material
• the light transmissive encapsulant/photoluminescence material mixture 466 can be contained within an annular-shaped wall 470.
• 4a and 4b could comprise solid-state excitation sources 420 constituted by two or more LEDs rather than a single broadband InGaN/GaN blue LED having an active region with multiple-quantum-wells.
• a green to yellow photoluminescence material refers to a material which generates light having a peak emission wavelength (l pe ) from ⁇ 490 nm to ⁇ 570 nm, that is in the green to yellow wavelength region of the visible spectrum.
• the green to yellow photoluminescence material has a broad emission characteristic and preferably has a FWHM (Full Width Half Maximum) of ⁇ 100 nm or wider.
• the green to yellow photoluminescence material can comprise any photoluminescence material, such as for example, garnet-based inorganic phosphor materials, silicate phosphor materials and oxynitride phosphor materials. Examples of suitable green to yellow phosphors are given in Table 1.
• the green to yellow photoluminescence materials comprises a cerium-activated yttrium aluminum garnet phosphor of general composition Y3(Al,Ga)5O12:Ce (YAG) such as for example a YAG series phosphor from Intematix Corporation, Fremont California, USA which have a peak emission wavelength from 527 nm to 543 nm and a FWHM of ⁇ 120 nm.
• YAG# represents the phosphor type - YAG – based phosphors - followed by the peak emission wavelength in nanometers (#).
• YAG535 denotes a YAG phosphor with a peak emission wavelength of 535 nm.
• the green to yellow photoluminescence material may comprise a cerium-activated yttrium aluminum garnet phosphor of general composition (Y,Ba)3(Al,Ga)5O12:Ce (YAG) such as for example a GNYAG series phosphor from Intematix Corporation, Fremont California, USA.
• the green photoluminescence material can comprise an aluminate (LuAG) phosphor of general composition Lu3Al5O12:Ce (GAL).
• Examples of such phosphors include for example the GAL series of phosphor from Intematix Corporation, Fremont California, USA which have a peak emission wavelength from 516 nm to 560 nm and a FWHM of ⁇ 120 nm.
• the notation GAL# represents the phosphor type (GAL) - LuAG– based phosphors - followed by the peak emission wavelength in nanometers (#).
• GAL520 denotes a GAL phosphor with a peak emission wavelength of 520 nm.
• green to yellow silicate phosphors include europium activated ortho- silicate phosphors of general composition (Ba, Sr)2SiO4: Eu such as for example G, EG, Y and EY series of phosphors from Intematix Corporation, Fremont California, USA which have a peak emission wavelength from 507 nm to 570 nm and a FWHM from ⁇ 70 nm to ⁇ 80 nm.
• the green to yellow phosphor can comprise a green-emitting oxynitride phosphor as taught in United States Patent US 8,679,367 entitled“Green-Emitting (Oxy) Nitride-Based Phosphors and Light Emitting Devices Using the Same” which is hereby incorporated in its entirety.
• a green-emitting oxynitride (ON) phosphor can have a general composition Eu 2+ :M 2+ Si4AlOxN(7-2x/3) where 0.1 £ x £ 1.0 and M 2+ is one or more divalent metal selected from the group consisting of Mg, Ca, Sr, Ba, and Zn.
• ON# represents the phosphor type (oxynitride) followed by the peak emission wavelength (lpe) in nanometers (#).
• ON495 denotes a green oxynitride phosphor with a peak emission wavelength of 495 nm.
• the orange to red photoluminescence material can comprise any orange to red photoluminescence material, typically a phosphor, that is excitable by blue light and operable to emit light with a peak emission wavelength lpe from about 600 nm to about 670 nm and can include, for example, a europium activated silicon nitride-based phosphor, a-SiAlON, Group IIA/IIB selenide sulfide-based phosphor or silicate-based phosphors. Examples of orange to red phosphors are given in Table 2.
• the europium activated silicon nitride-based phosphor comprises a Calcium Aluminum Silicon Nitride phosphor (CASN) of general formula CaAlSiN 3 :Eu 2+ .
• the CASN phosphor can be doped with other elements such as strontium (Sr), general formula (Sr,Ca)AlSiN3:Eu 2+ .
• the notation CASN# represents the phosphor type (CASN) followed by the peak emission wavelength (lpe) in nanometers (#).
• CASN615 denotes an orange to red CASN phosphor with a peak emission wavelength of 615 nm.
• the orange to red phosphor can comprise an orange to red- emitting phosphor as taught in United States Patent US 8,597,545 entitled“Red-Emitting Nitride-Based Calcium-Stabilized Phosphors” which is hereby incorporated in its entirety.
• Such a red emitting phosphor comprises a nitride-based composition represented by the chemical formula M a Sr b Si c Al d N e Eu f , wherein: M is Ca, and 0.1 £ a £ 0.4; 1.5 ⁇ b ⁇ 2.5; 4.0 £ c £ 5.0; 0.1 £ d £ 0.15; 7.5 ⁇ e ⁇ 8.5; and 0 ⁇ f ⁇ 0.1; wherein a+b+f >2+d/v and v is the valence of M.
• the orange to red phosphor can comprise an orange to red emitting nitride-based phosphor as taught in United States Patent US 8,663,502 entitled“Red-Emitting Nitride-Based Phosphors” which is hereby incorporated in its entirety.
• Such a red emitting phosphor comprising a nitride-based composition represented by the chemical formula M(x/v)M ⁇ 2Si5-xAlxN8 :RE, wherein: M is at least one monovalent, divalent or trivalent metal with valence v; M ⁇ is at least one of Mg, Ca, Sr, Ba, and Zn; and RE is at least one of Eu, Ce, Tb, Pr, and Mn; wherein x satisfies 0.1£ x ⁇ 0.4, and wherein said red-emitting phosphor has the general crystalline structure of M ⁇ 2Si5N8:RE, Al substitutes for Si within said general crystalline structure, and M is located within said general crystalline structure substantially at the interstitial sites.
• M is at least one monovalent, divalent or trivalent metal with valence v
• M ⁇ is at least one of Mg, Ca, Sr, Ba, and Zn
• RE is at least one of Eu, Ce, Tb,
• Orange to red phosphors can also include Group IIA/IIB selenide sulfide-based phosphors.
• a first example of a Group IIA/IIB selenide sulfide-based phosphor material has a composition MSe 1-x S x :Eu, wherein M is at least one of Mg, Ca, Sr, Ba and Zn and 0 ⁇ x ⁇ 1.0.
• a particular example of this phosphor material is CSS phosphor (CaSe1-xSx:Eu).
• CSS phosphors are provided in co-pending United States patent application Publication Number US2017/0145309 filed 30 September 2016, which is hereby incorporated by reference in its entirety.
• the CSS orange to red phosphors described in United States patent publication US2017/0145309 can be used in the present invention.
• the emission peak wavelength of the CSS phosphor can be tuned from 600 nm to 650 nm by altering the S/Se ratio in the composition and exhibits a narrow-band red emission spectrum with FWHM from ⁇ 48 nm to ⁇ 60 nm (longer peak emission wavelength typically has a larger FWHM value).
• the notation CSS# represents the phosphor type (CSS) followed by the peak emission wavelength in nanometers (#).
• CSS615 denotes a CSS phosphor with a peak emission wavelength of 615 nm.
• the CSS phosphor particles can be coated with one or more oxides, for example: aluminum oxide (Al2O3), silicon oxide (SiO2), titanium oxide (TiO 2 ), zinc oxide (ZnO), magnesium oxide (MgO), zirconium oxide (ZrO 2 ), boron oxide (B 2 O 3 ) or chromium oxide (CrO).
• the narrow-band red phosphor particles may be coated with one or more fluorides, for example: calcium fluoride (CaF 2 ), magnesium fluoride (MgF 2 ), zinc fluoride (ZnF 2 ), aluminum fluoride (AlF 3 ) or titanium fluoride (TiF 4 ).
• the coatings may be a single layer, or multiple layers with combinations of the aforesaid coatings.
• the combination coatings may be coatings with an abrupt transition between the first and second materials, or may be coatings in which there is a gradual/smooth transition from the first material to the second material thus forming a zone with mixed composition that varies through the thickness of the coating.
• the orange to red phosphor can comprise an orange-emitting silicate-based phosphor as taught in United States Patent US 7,655,156 entitled“Silicate-Based Orange Phosphors” which is hereby incorporated in its entirety.
• Such an orange-emitting silicate–based phosphor can have a general composition (Sr1-xMx)yEuzSiO5 where 0 ⁇ x £ 0.5, 2.6 £ y £ 3.3, 0.001 £ z £ 0.5 and M is one or more divalent metal selected from the group consisting of Ba, Mg, Ca, and Zn.
• the notation O# represents the phosphor type (orange silicate) followed by the peak emission wavelength (lpe) in nanometers (#).
• O600 denotes an orange silicate phosphor with a peak emission wavelength of 600 nm.
• embodiments of the invention concern full spectrum white light emitting devices that generate full spectrum light that closely resembles natural light, in particular although not exclusively, in the in blue to cyan wavelength region (430 nm to 520 nm) of the visible spectrum where human non-visual perception, as for example, measured by CAF (Circadian Action Factor) are affected most.
• the invention concerns improving the efficacy of full spectrum white light emitting devices while maintaining the spectrum close to the natural light in the wavelength ranging from about 430 nm to about 520 nm.
• the efficacy of full spectrum white light emitting devices can be improved by optimizing (reducing) the intensity of light (photon count) at wavelengths corresponding to red region of the spectrum, in particular reducing light intensity at wavelengths that affect the values of CRI R9 -“Saturated Red” and CRI R8 -“Reddish Purple”.
• Such an improvement in efficacy can be achieved by including of an orange to red photoluminescence material whose peak emission wavelength/FWHM is selected such that the device generates full spectrum white light having a spectrum with an intensity roll-off (tail) in the orange to red wavelength region of the visible spectrum that decreases (drops) to half its maximum intensity in a wavelength from about 645 nm to about 695 nm.
• FIG. 5 shows: (A) intensity spectra, normalized intensity I versus wavelength (nm) for: (i) a known full spectrum light emitting device that utilizes a narrowband excitation source - spectrum denoted A (dotted line), (ii) a full spectrum light emitting device in accordance with the invention that utilizes a broadband excitation source - spectrum denoted B (thin solid line), (iii) black-body curve (bbc) (dashed line) for a CCT that is nominally the same as that of spectra A and B, and (B) Circadian Action Spectrum (CAS)– thick solid line, Relative Quantum Sensitivity versus wavelength (nm).
• A intensity spectra, normalized intensity I versus wavelength (nm) for: (i) a known full spectrum light emitting device that utilizes a narrowband excitation source - spectrum denoted A (dotted line), (ii) a full spectrum light emitting device in accordance with the invention that utilizes a broadband excitation source
• Circadian Action Spectrum also referred to as spectral circadian efficiency function c(l)
• c(l) represents human non-visual relative sensitivity to light.
• the maximum sensitivity of c(l) occurs at a wavelength of 460 nm.
• the CAS suggests that the 430 nm to 520 nm portion of the spectrum as being the most significant wavelengths for providing circadian input for regulating melatonin secretion.
• spectrum A exhibits a peak 580, corresponding to the excitation light generated by the narrowband excitation source, whose intensity deviates significantly from that of the bbc (i.e. peak intensity is very much higher than that of the bbc at the same wavelength).
• spectrum B exhibits two peaks 582, 584, corresponding to the excitation light generated by the broadband excitation source whose intensity, compared with spectrum A, deviates only slightly from that of the bbc (i.e. the peak intensities are slightly higher than the bbc at the same wavelengths).
• the peak 580 occurs at a wavelength of 455 nm that is close to the maximum sensitivity of the CAS which is at a wavelength of 460 nm.
• spectrum A exhibits a trough (valley) 586 whose minimum intensity deviates significantly from that of the bbc (i.e. the trough intensity is much lower than the bbc).
• spectrum B exhibits a trough (valley) 588 that whose minimum intensity, compared with spectrum A, deviates only slightly from that of the bbc (i.e. the trough intensity is slight lower than the bbc).
• the smaller deviation of emission peaks 582 and 584 of spectrum B (compared with peak 584 of spectrum A) and the smaller deviation of trough 588 of spectrum B (compared with trough 586 of spectrum A) from the bbc indicates that spectrum B more closely resembles the bbc (Plankian spectrum) over a wavelength range from 430 nm to 520 nm (blue to cyan). It will be further appreciated that spectrum B more closely resembles natural light over this wavelength region where human non-visual perception measured by CAF (Circadian Action Factor) are affected most and this can be beneficial to human wellbeing.
• CAF Circadian Action Factor
• a metric for quantifying how closely the spectrum resembles the bbc is a maximum (largest) percentage intensity deviation (Imaxdev) from the intensity of light of the bbc of the same Correlated Color Temperature. That is, over a wavelength range from about 430 nm to 520 nm, I maxdev is the maximum (largest) percentage intensity difference between the intensity of the spectrum and the intensity of the bbc.
• the maximum deviation can be positive (such as a peak where the spectrum intensity is greater than the bbc) or negative (such as a trough where the spectrum intensity is less than the bbc).
• each spectra is normalized to have the same CIE 1931 XYZ relative luminance Y.
• the spectrum is normalized using the photopic luminosity function y(l) - sometimes referred to as the photopic or visual luminous efficiency function v(l) - of a standard observer which takes account of the photopic (visual) response of an observer and are for the same correlated color temperature.
• Imaxdev is thus the maximum (greatest) percentage intensity difference between the normalized intensity of the spectrum and the normalized intensity of the bbc over a wavelength range from about 430 nm to 520 nm.
• spectrum B has a maximum percentage intensity deviation Imaxdev of only 30% (corresponding to peak 582), that is the normalized intensity of spectrum A at wavelength lmaxdev is 130% of the normalized intensity of the bbc at this wavelength.
• Roll-off wavelength, lRO is defined as the wavelength at which the normalized intensity (I) decreases from its maximum intensity (denoted Imax) in the orange to region of the spectrum to half its maximum intensity (denoted 1 ⁇ 2 I max ).
• the maximum intensity Imax within this wavelength region of the spectrum corresponds to photoluminescence converted light and the maximum intensity occurs at a wavelength longer than about 570 nm. For instance, the maximum intensity may occur at wavelength ranging from about 590 nm to about 620 nm.
• the packaged test method involves measuring total light emission of a packaged white light emitting device (FIG.3a) in an integrating sphere.
• each excitation source comprises one or more solid-state light sources of a single dominant wavelength
• Dev.# denotes a white light emitting device in accordance with an embodiment of the invention in which each excitation source comprises solid-state light sources of two different dominant wavelengths.
• Tables 3, 4 and 5 tabulate measured optical test data for 2700K white light emitting devices Dev.1, Dev.2 and a known CRI90 comparative device Com.1 and illustrate the effect on efficacy of reducing the red spectral content while maintaining the blue and cyan spectral content.
• Dev.1 comprises a combination of GAL520 and CASN650 phosphors and
• Dev.2 comprises a combination of GAL520, GAL530, CASN625 and CASN650 phosphors.
• the combination of CASN625 and CASN650 produces a peak emission of about 628 nm with the wavelength depending on the relative proportion of CASN625 to CASN650.
• Comparative device Com.1 comprises a known 2835 packaged white light emitting device which utilizes a narrowband excitation source and has a nominal CRI Ra of 90.
• the data are normalized using the CIE 1931 luminosity function y(l) of a standard observer which takes account of the photopic response of an observer.
• the Plankian spectrum (curve) or black-body curve in FIG. 6 represents the spectrum for a General CRI Ra equal to 100 for a given color temperature (CCT). Accordingly, for a white light emitting device of a given color temperature to have the highest color rendering possible, its emission spectrum should match as closely as possible the black-body spectrum of the same color temperature.
• the reduction of the blue emission peak 682 of devices Dev.1 and Dev.2 results in the emission spectrum more closely resembling the Plankian spectrum (that is more closely resembling natural sunlight) over a wavelength range 430 nm to 520 nm (blue to cyan).
• devices Dev.1 and Dev.2 thus produce white light that more closely resembles natural light over this wavelength region where human non-visual perception measured by CAF (Circadian Action Factor) are affected most and this can be beneficial to human wellbeing. It is believed that this change in spectral energy content resulting from the use of a broadband blue excitation source that at least partially fills the trough in the cyan region of the spectrum and reduces the peak overshoot in the blue region accounts for the superior color rendering properties of the devices of the invention. As can be seen from Table 3, devices Dev.1 and Dev.2 produce white light having a CAF that is within 1.9% and 0.8% respectively of that of natural light (bbc for a CCT 2700K). In comparison, comparative device Com.1 has a CAF that is within 3.8% of that of natural light.
• the intensity roll-off (tail) of the spectra in the orange to red wavelength region of the spectrum i.e. for wavelength longer than about 570 nm.
• the maximum peak intensity (I max Dev.1) is about 8.2 and this occurs at a wavelength of about 640 nm.
• the intensity (I) drops to half this value (1 ⁇ 2 I max Dev.1) at a wavelength (l RO Dev. 1) of about 690 nm.
• the maximum peak intensity (I max Dev.2) is about 7.6 and this occurs at a wavelength of about 620 nm.
• the intensity (I) drops to half this value (1 ⁇ 2 I max Dev.2) at a wavelength (lRO Dev.2) of about 675 nm.
• device Dev.1 has an efficacy of 104 lm/W and produces white light with a CRI Ra greater than or equal to 95 (96.9) with each of CRI R1 to CRI R15 being 90 or higher (91.2 to 99.0).
• device Dev.2 has an efficacy of 119 lm/W and produces white light with a CRI Ra greater than or equal to 95 (95.8) in which CRI R1 to CRI R7 and CRI R10 to CRI R15 are about 90 or higher (89.5 to 99.3), while CRI R8 (corresponding to“Reddish Purple”) is greater than 72 and less than 90 (86.6), while CRI R9 (corresponding to“Saturated Red”) is greater than 50 and less than 90 (69.6). Further, it is to be noted that while the quality of light produced by Dev.2 is substantially the same as that of Dev.1, the efficacy increases substantially by about 15% (from 104 lm/W to 119 lm/W).
• Tables 6, 7 and 8 tabulate measured optical test data for 3000K white light emitting devices Dev.3 to Dev.5 and known 3000K CRI90 and CRI80 comparative devices Com.2 and Com.3 respectively and illustrate the effect on efficacy of reducing the red spectral content while maintaining the blue and cyan spectral content.
• Dev.3 comprises a combination of GAL520 and CASN650 phosphors while devices Dev.4 and Dev.5 a combination of GAL520, GAL530, CASN625 and CASN650 phosphors in which Dev.5 comprises a greater relative portion of CASN625 to CASN650 than Dev.4 (the combination of CASN625 and CASN650 in Dev.4 produces a peak emission of about 625 nm and the combination in Dev.5 produces a peak emission of about 628 nm).
• Comparative device Com.2 comprises a known 2835 packaged white light emitting device which utilizes a narrowband excitation source and has a nominal CRI Ra of 90.
• Com.3 comprises a known 2835 packaged white light emitting device which utilizes a narrowband excitation source and has a nominal CRI Ra of 80.
• each of devices Dev.3, Dev.4 and Dev.5 thus produce white light that more closely resembles natural light over this wavelength region where human non- visual perception measured by CAF (Circadian Action Factor) or Melanopic Ratio (MR) are affected most and this can be beneficial to human wellbeing.
• CAF Circadian Action Factor
• MR Melanopic Ratio
• the maximum peak intensity (I max Dev.4) is about 6.8 and this occurs at a wavelength of about 625 nm.
• the intensity (I) drops to half this value (1 ⁇ 2 Imax Dev.4) at a wavelength (lRO Dev.4) of about 680 nm.
• the maximum peak intensity (I max Dev.5) is about 7.0 and this occurs at a wavelength of about 605 nm.
• the intensity (I) drops to half this value (1 ⁇ 2 I max Dev.5) at a wavelength (lRO Dev.5) of about 650 nm.
• device Dev.3 has an efficacy of 109 lm/W and produces white light with a CRI Ra greater than 95 (95.9) with each of CRI R1 to CRI R15 is 90 or higher (91.8 to 99.3).
• device Dev.4 has a efficacy of 149 lm/W and produces white light with a CRI Ra greater than 95 (95.6) with each of CRI R1 to CRI R8 and CRI R10 to CRI R15 is 90 or higher while CRI R9 (corresponding to“Saturated Red”) is greater than 50 and less than 90 (77.8).
• device Dev.5 has a efficacy of 120 lm/W and produces white light with a CRI Ra greater than or equal to 85 (85.0) with each of CRI R1 to CRI R7 and CRI R10 to CRI R15 is 90 or higher, while CRI R8 (corresponding to“Reddish Purple”) is less than 72 (60.0), while CRI R9 (corresponding to“Saturated Red”) is greater than 10 and less than 90 (11.9).
• the efficacy increases substantially by about 20% and 50% respectively.
• Tables 9, 10 and 11 tabulate measured optical test data for 4000K white light emitting devices Dev.6 and a known 4000K CRI90 comparative device Com.4.
• Comparative device Com.4 comprises a known 2835 packaged white light emitting device which utilizes a narrowband excitation source and has a nominal CRI Ra of 90.
• Dev.6 generates white light having a CAF that is 0.4% of that of natural light (bbc for a CCT 4000K).
• comparative device Com.3 has a CAF that is only within 7.0% of that of natural light.
• device Dev.6 produces white light that more closely resembles natural light over this wavelength region where human non-visual perception measured by CAF (Circadian Action Factor) or Melanopic Ratio (MR) are affected most and this can be beneficial to human wellbeing.
• CAF Circadian Action Factor
• MR Melanopic Ratio
• device Dev.6 has an efficacy of 117 lm/W and produces white light with a CRI Ra greater than 95 (95.9) with each of CRI R1 to CRI R15 is 90 or higher (91.8 to 99.3).
• 5000K full spectrum white light emitting devices test data
• Tables 12, 13 and 14 tabulate measured optical test data for 5000K white light emitting devices Dev.7 and Dev.8 and known 5000K CRI90 and CRI80 comparative devices Com.5 and Com.6 respectively and illustrate the effect on efficacy of reducing the red spectral content while maintaining the blue and cyan spectral content.
• Dev.7 comprises a combination of GAL520 and CASN650 phosphors while devices Dev.8 a combination of GAL520, GAL530, CASN625 and CASN650 phosphors.
• Comparative device Com.5 comprises a known 2835 packaged white light emitting device which utilizes a narrowband excitation source and has a nominal CRI Ra of 90.
• Com.6 comprises a known 2835 packaged white light emitting device which utilizes a narrowband excitation source and has a nominal CRI Ra of 80.
• each of devices Dev.7 and Dev.8 produce white light that more closely resembles natural light over this wavelength region where human non-visual perception measured by CAF (Circadian Action Factor) or Melanopic Ratio (MR) are affected most and this can be beneficial to human wellbeing.
• CAF Circadian Action Factor
• MR Melanopic Ratio
• the maximum peak intensity (Imax Dev.8) is about 5.6 and this occurs at a wavelength of about 590 nm.
• the intensity (I) drops to half this value (1 ⁇ 2 I max Dev.8) at a wavelength (lRO Dev.8) of about 650 nm.
• device Dev.7 has an efficacy of 117 lm/W and produces white light with a CRI Ra greater than 95 (98.5) in which each of CRI R1 to CRI R15 is 90 or higher (93.5 to 99.0).
• device Dev.8 has an efficacy of 152 lm/W and produces white light with a CRI Ra greater than 80 (83.9), while CRI R8 (corresponding to“Reddish Purple”) is less than 72 (62.6), while CRI R9 (corresponding to “Saturated Red”) is greater than zero and less than 90 (1.3).
• the quality of light produced by Dev.8 is substantially the same as that of Dev.7 the efficacy increase substantially by about 30% and is comparable with Com.6.
• the white light emitting devices according to embodiments of the invention have been described with reference to remote phosphor and packaged white light emitting devices, it will be appreciated that the category of white light emitting devices encompasses LED-filaments white light emitting devices. Tests have confirmed that white light emitting devices in the form of LED-filaments in accordance with embodiments of the invention have similar spectral characteristics and provide the same benefits and advantages of the white light emitting devices described above.
• FIG. 10 illustrates a side view of an LED-filament A-Series lamp (bulb) 10100 for generating full spectrum white light with a CCT (Correlated Color Temperature) in a range 1800 K to 6800K.
• the LED-filament lamp 10100 comprises a connector base 10102, a light- transmissive glass envelope 10104; a glass LED-filament support (stem) 10106 and four LED- filaments (white light emitting devices) 1010 in accordance with the invention.
• the LED-filament 1110 can comprise a light-transmissive circuit board (substrate) 11108 having an array of solid-state broadband excitation sources 1120 mounted on a front face 11110.
• the broadband excitation sources are configured to generate broadband blue excitation light with a dominant wavelength l d from 420 nm to 470 nm, that is, in the blue wavelength region of the visible spectrum with a FWHM from 25 nm to 50 nm.
• the broadband excitation sources 1120 are constituted by unpackaged broadband blue LED dies (for example MQW InGaN/GaN LED dies described herein) which are mounted directly to the substrate.
• each of the broadband excitation sources 1120 may be constituted by a combination of at least two narrowband blue LED dies having different respective dominant wavelengths ld1 ld2 which are mounted directly to the substrate.
• the substrate 11108 is planar and has an elongate form (strip) with the broadband excitation sources 1120 being configured as a linear array along the length of the front face 11110 of the substrate.
• each LED-filament can comprise twenty five excitation sources (LED dies) with a total nominal power of about 2W.
• the substrate 11108 which is preferably at least translucent can comprise any light- transmissive material with a transmittance to visible light of 10% or greater such as for example glass or a plastics material such as polypropylene, silicone or an acrylic.
• the substrate 11108 can on the front face 11110 further comprise electrically conductive tracks 11112 configured in a desired circuit configuration for electrically connecting the excitation sources 1120.
• the excitation sources 1120 can be electrically connected serially as a string.
• the excitation sources 1120 can be electrically connected to the conducting tracks 11112 using bond wires 11114.
• the excitation sources 1120 can be directly connect to each other by means of bond wires thereby eliminating the need for the conducting tracks.
• the excitation sources 1120 can comprise surface mountable or flip-chip LEDs mounted to the conducting tracks.
• the substrate 11108 can, at respective ends, comprise electrodes 11116 for applying electrical power to the LED-filament 1110.
• the LED-filament 1110 further comprises a photoluminescence wavelength conversion material 1166 covering at least the front face 11110 of the substrate and excitation sources 1120.
• the photoluminescence wavelength conversion material 1166 comprises a combination green to yellow photoluminescence materials and optionally orange to red photoluminescence materials.
• the LED-filament 1110 may, as shown, further comprises a photoluminescence wavelength conversion material 11118 covering the back face 11120 of the substrate.
• the photoluminescence wavelength conversion material 11118 can comprise the same photoluminescence material as the photoluminescence wavelength conversion material 1166.
• a particular advantage of the present invention is that full spectrum white light emitting devices according to embodiments of the invention can generate full spectrum light that closely resembles natural light in blue to cyan wavelength region (430 nm to 520 nm) of the spectrum where human non-visual perception measured by CAF (Circadian Action Factor) or Melanopic Ratio (MR) are affected most.
• CAF Circadian Action Factor
• MR Melanopic Ratio
• CAF Circadian Action Factor typically is modulated by blue content throughout the day. At noon time the sun has a high CCT and higher blue to cyan content. Sunrise and sunset have a lower CCT and lower blue to cyan content. CAF value of natural light at a different CCT is a good measure of the lighting deviation from the nature light in blue to cyan region where human emotional, health, or wellbeing life are affected.
• a further advantage of full spectrum white lighting emitting devices of the present invention is that, through appropriate selection of the peak emission wavelength/FWHM of the orange to red photoluminescence material, the device generates white light with a spectrum having a roll-off (tail) in the orange to red wavelength region where the intensity decreases from its maximum value in the orange to red wavelength region of the spectrum to about 50% of said maximum value at a wavelength from about 645 nm to about 695 nm.
• a spectral characteristic reduces light intensity (photon count) in the red wavelength region of the spectrum at which wavelengths the photopic response of the eye is low and thereby increasing device efficacy.
• Test data has confirmed that full spectrum white light emitting devices in accordance with the invention can generate white light with a CRI Ra of at least 90 and an efficacy which equals that or exceeds that of known CRI80 devices while having a reduction in only CRI R9 and CRI R8.
• CRI Ra of at least 90
• an efficacy which equals that or exceeds that of known CRI80 devices while having a reduction in only CRI R9 and CRI R8.
• the perceived quality of light generated by the device is not adversely affected due to the sensitivity of the eye in the red wavelength region of the spectrum.
• light emitting devices in accordance with the invention comprising a broadband solid-state excitation source enable the implementation of full spectrum white light emitting devices that are characterized by generating white light having a color temperature in a range 1800K to 6800K with one or more of: (i) over a wavelength range from about 430 nm to about 520 nm, a maximum percentage intensity deviation of said white light from the intensity of light of a black-body curve or CIE Standard Illuminant D of the same Correlated Color Temperature is less than at least one of 60%, 50%, 40%, 30%, 20% and 10%; (ii) a spectrum having a CAF that is within 5%, 4%, 2%, or 1% of the black-body curve/CIE Standard Illuminant D; (iii) a CRI R9 and/or a CRI R8 that is less than 90, (iv) a spectrum whose intensity decreases from its maximum value in the orange to red wavelength region of the spectrum to about 50% of said

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