Abstract:
A photoluminescence wavelength conversion component comprises a first portion having at least one photoluminescence material; and a second portion comprising light reflective material, wherein the first portion is integrated with the second portion to form the photoluminescence wavelength conversion component.

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of priority to U.S. Provisional Application No. 61/801,493, filed on Mar. 15, 2013, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     This disclosure relates to photoluminescence wavelength conversion components for use with solid-state light emitting devices to generate a desired color of light. 
     BACKGROUND 
     White light emitting LEDs (“white LEDs”) are known and are a relatively recent innovation. It was not until LEDs emitting in the blue/ultraviolet part of the electromagnetic spectrum were developed that it became practical to develop white light sources based on LEDs. As taught, for example in U.S. Pat. No. 5,998,925, white LEDs include one or more one or more photoluminescent materials (e.g., phosphor materials), which absorb a portion of the radiation emitted by the LED and re-emit light of a different color (wavelength). Typically, the LED chip or die generates blue light and the phosphor(s) absorbs a percentage of the blue light and re-emits yellow light or a combination of green and red light, green and yellow light, green and orange or yellow and red light. 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 nearly white in color. Alternatively, the LED chip or die may generate ultraviolet (UV) light, in which phosphor(s) to absorb the UV light to re-emit a combination of different colors of photoluminescent light that appear white to the human eye. 
     Due to their long operating life expectancy (&gt;50,000 hours) and high luminous efficacy (70 lumens per watt and higher) high brightness white LEDs are increasingly being used to replace conventional fluorescent, compact fluorescent and incandescent light sources. 
     Typically the phosphor material is mixed with light transmissive materials, such as silicone or epoxy material, and the mixture applied to the light emitting surface of the LED die. It is also known to provide the phosphor material as a layer on, or incorporate the phosphor material within, an optical component, a phosphor wavelength conversion component, that is located remotely to the LED die (“remote phosphor” LED devices). 
       FIG. 1  shows one possible approach that can be taken to implement a lighting device  100  when using a wavelength conversion component  102 . The wavelength conversion component  102  includes a photoluminescence layer  106  having phosphor materials that are deposited onto an optically transparent substrate layer  104 . The phosphor materials within the photoluminescence layer  106  generate photoluminescence light in response to excitation light emitted by an LED die  110 . The LED die  110  is attached to a MCPCB  160 . The wavelength conversion component  102  and the MCPCB  160  are both mounted onto a thermally conductive base  112 . 
     The wavelength conversion component  102  is manufactured to include a protruding portion  108  along the bottom. During assembly of the lighting device  100 , the protruding portion  108  acts as an attachment point that fits within a recess formed by mounting portion  116  of the thermally conductive base  112 . 
     To increase the light emission efficiency of the lighting device  100 , a reflective material  114  is placed onto the thermally conductive base  112 . Since the light emitted by the phosphor materials in the photoluminescence layer  106  is isotropic, this means that much of the emitted light from this component is projected in a downwards direction. As a result, the reflective material  114  is necessary to make sure that the light emitted in the downwards direction is not wasted, but is instead reflected to be emitted outwardly to contribute the overall light output of the lighting device  100 . 
     One problem with this approach is that adding the reflective material  114  to the base  112  requires an additional assembly step during manufacture of the lighting device. Moreover, significant material costs are required to purchase the reflective material  114  for the light assembly. In addition, it is possible that the reflective surface of the reflective material  114  may end up damaged during shipping or assembly, thereby reducing the reflective efficiencies of the material. An organization may also incur additional administrative costs to identify and source the reflective materials. 
     Another problem with this type of configuration is that light emitted from the lower levels of the photoluminescence layer  106  can be blocked by the mounting portion  116  on the base  112 . This effectively reduces the lighting efficiency of the lighting device  100 . Since phosphor materials are a relatively expensive proportion of the cost of the lighting device, this wastage of the light from the lower portions of the wavelength conversion component  102  means that an excessive amount of costs was required to manufacture the phosphor portion of the product without receiving corresponding amounts of lighting benefits. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention concern an integrated lighting component that includes both a wavelength conversion portion and a reflector portion and may optionally further include a third optical portion which can include a light diffusive material. 
     According to one embodiment a photoluminescence wavelength conversion component comprises: a first portion having at least one photoluminescence material; and a second portion comprising light reflective material, wherein the first portion is integrated with the second portion to form the photoluminescence wavelength conversion component. In some embodiments the component further comprises a third optical portion. The third optical portion can comprise a lens. Alternatively, and or in addition, the third optical portion can comprise a light diffusive material. In preferred embodiments the light diffusive material comprises nano-particles. 
     Preferably the first portion, second portion and or third portions have matching indices of refraction and each can be manufactured from the same base material. 
     The component having the first portion, the second portion and/or third portion can be co-extruded. For example, where the component has a constant cross section the first portion, the second portion and/or third portion can be co-extruded. 
     In some embodiments the at least one photoluminescence material is incorporated in and homogeneously distributed throughout the volume of the first portion. 
     The second portion can comprise an angled slope. To reduce light loss the angled slope extends from a base of the first portion to a top of an attachment portion of the component. 
     According to another embodiment, a method of manufacturing a lamp, comprises: receiving an integrated photoluminescence wavelength conversion component, wherein the photoluminescence wavelength conversion component comprises a first portion having at least one photoluminescence material and a second portion comprising light reflective material, wherein the first portion is integrated with the second portion to form the photoluminescence lighting component; and assembling the lamp by attaching the integrated photoluminescence wavelength conversion component to a base component, such that the integrated photoluminescence wavelength conversion component is attached to the base portion without separately attaching the first portion and the second portion to the base portion. 
     According to an embodiment of the invention a method of manufacturing a photoluminescence wavelength conversion component, comprises: extruding a first portion having at least one photoluminescence material; and co-extruding a second portion comprising light reflective material, wherein the first portion is integrated with the second portion to form the photoluminescence wavelength conversion component. Advantageously the method further comprises co-extruding a third optical portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the present invention is better understood LED-based light emitting devices and photoluminescence wavelength conversion components in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which like reference numerals are used to denote like parts, and in which: 
         FIG. 1  shows an end view of a linear lamp as previously described; 
         FIG. 2  is a schematic end view of an integrated photoluminescence wavelength conversion component in accordance with an embodiment of the invention; 
         FIG. 3  is a perspective view of the component of  FIG. 2 ; 
         FIG. 4  is a schematic sectional view of an integrated photoluminescence wavelength conversion component in accordance with an embodiment of the invention; 
         FIG. 5  is a schematic end view of an LED-based linear lamp utilizing the photoluminescence wavelength conversion component of  FIGS. 2 and 3 ; 
         FIG. 6  is a schematic end view of an integrated photoluminescence wavelength conversion component in accordance with an embodiment of the invention; 
         FIG. 7  is a schematic sectional view of an integrated photoluminescence wavelength conversion component in accordance with an embodiment of the invention; 
         FIG. 8  is a schematic sectional view of an integrated photoluminescence wavelength conversion component in accordance with an embodiment of the invention; and 
         FIG. 9  is a schematic end view of an LED-based reflector lamp utilizing the photoluminescence wavelength conversion component of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Some embodiments of the invention are directed to an integrated lighting component that includes both a wavelength conversion portion and a reflector portion.  FIG. 2  illustrates an end view of an integrated component  10  that includes both a wavelength conversion layer  20 , a an optical component portion  22  and a reflector portion  25 . The optical component portion  22  can be implemented as an optically transparent substrate or lens upon which the materials of the wavelength conversion layer  20  have been deposited. The integrated component  10  also includes feet/extended portions  15 . These extended portions  15  are to assemble component  10  to a base, by inserting the extended portions  15  within a matching recess on the base portion. 
     By integrating both the wavelength conversion portion  20  and the reflector portion  25  into a unitary component, this avoids many of the problems associated with having them as separate components. Recall that the alternative approach of having separate components requires a step to assemble the reflective component onto a base, followed by an entirely separate step to then place the wavelength conversion component onto the exact same base. With the present invention, the integrated component can be assembled to the base without requiring separate actions for the reflective component and the wavelength conversion component. Instead, both are assembled to the base in the present approach by assembly the single integrated component  10  to the base. 
     In addition, significant material cost savings can be achieved with the present invention. The overall cost of the integrated component is generally less expensive to manufacture as compared to the combined costs of having a separate wavelength conversion component and a separate reflector component. A separate reflector component (such as a light reflective tape) typically includes, for example, a substrate for the reflective materials (e.g., paper materials) and an adhesive portion on the underside to form the adhesive tape properties, with these costs passed on to the purchaser of the reflector product. In addition, separate packaging costs would also exist for the separate reflector component, which would likewise be passed onto the purchaser of the product. Moreover, an organization may incur additional administrative costs to identify and source the separate reflective component. By providing an integrated component that integrates the reflector portion with the wavelength conversion portion, many of these additional costs can be avoided. 
     Furthermore, it can be seen that the reflective surface of the reflector portion  25  is within the interior of the component  10 . This makes it less likely that the reflective properties of the reflector portion  25  could be accidentally damaged, e.g., during assembly or shipping. In contrast, a separate reflector component has its reflective portion exposed, creating a greater risk that the reflective surface may end up damaged during shipping or assembly. Any damage to the reflective surface could reduce the reflective efficiencies of the material, which may consequently reduce the overall lighting efficiency of the lighting device that uses the separate reflector component. 
     The present invention also provides better light conversion efficiencies for the phosphor materials of the wavelength conversion layer  20 . As previously discussed, one problem with the configuration of  FIG. 1  that has feet/extended portions  108  is that light emitted from the lower levels of the wavelength conversion layer can be blocked by the mounting portion  116  on base  112 . This effectively reduces the lighting efficiency of the lighting device  100 . Since phosphor materials are a relatively expensive proportion of the cost of the lighting device, this wastage of the light from the lower portions of the wavelength conversion component  102  means that an excessive amount of costs was required to manufacture the phosphor portion of the product without receiving corresponding amounts of lighting benefits. 
     In the present invention, the integrated nature of the component  10  allows the reflector portion  25  to assume any appropriate configuration relative to the rest of the component  10 . As shown in  FIG. 2 , this embodiment has the reflector portion  25  configured such that it slopes upward from the bottom of the wavelength conversion layer  20  up towards the upper height of the feet  15 . This angled implementation of the reflector portion  25  means that light produced by the bottom portion of the wavelength conversion layer  20  will tend to reflect outwards from the bottom of the light, rather than towards the sides of the light. Therefore, less of the phosphor-generated light will be blocked by the mounting portion  116  or within the recess created by mounting portion  116 . As a result, greater lighting emission efficiencies can be achieved, which means that less phosphor materials are required to otherwise achieve the same relative light output as the prior art lighting products. 
     Lighting products and lamps that employ the present invention can be configured to have any suitable shape or form. In general, lamps (light bulbs) are available in a number of forms, and are often standardly referenced by a combination of letters and numbers. The letter designation of a lamp typically refers to the particular shape of type of that lamp, such as General Service (A, mushroom), High Wattage General Service (PS—pear shaped), Decorative (B—candle, CA—twisted candle, BA—bent-tip candle, F—flame, P—fancy round, G—globe), Reflector (R), Parabolic aluminized reflector (PAR) and Multifaceted reflector (MR). The number designation refers to the size of a lamp, often by indicating the diameter of a lamp in units of eighths of an inch. Thus, an A- 19  type lamp refers to a general service lamp (bulb) whose shape is referred to by the letter “A” and has a maximum diameter two and three eights of an inch. As of the time of filing of this patent document, the most commonly used household “light bulb” is the lamp having the A- 19  envelope, which in the United States is commonly sold with an E 26  screw base. 
       FIGS. 3 and 4  illustrate two example different lamps that can be implemented using the integrated component of the present invention. 
       FIG. 3  illustrates an integrated component  10  for a linear lamp. This version of the integrated component  10  has a body that is extended in a lengthwise direction, with the same cross-sectional profile shown in  FIG. 2  running throughout the length of the body. To assemble a linear lamp, the component  10  of  FIG. 3  is mounted onto a base, where an array of LEDs is placed at spaced intervals within/under the interior of the component  10 . 
       FIG. 4  illustrates a cross sectional view of an integrated component having a shape that is generally a dome. In this approach, the feet  15  extend in either a full or partial circular pattern around the base of the component  10 . The reflector  25  has an annular profile that forms the base of the component  10 . 
       FIG. 5  illustrates an LED-based linear lamp  50  in accordance with embodiments of the invention, where the integrated component  10  (i.e. the component of  FIG. 2 ) is mounted to a base  40 . The base  40  is made of a material with a high thermal conductivity (typically ≧150 Wm −1 K −1 , preferably ≧200 Wm −1 K −1 ) such as for example aluminum (≈250 Wm −1 K −1 ), an alloy of aluminum, a magnesium alloy, a metal loaded plastics material such as a polymer, for example an epoxy. Conveniently the base  40  can be extruded, die cast (e.g., when it comprises a metal alloy) and/or molded, by for example injection molding (e.g., when it comprises a metal loaded polymer). 
     One or more solid-state light emitter  110  is/are mounted on a substrate  160 . In some embodiments, the substrate  160  comprises a circular MCPCB (Metal Core Printed Circuit Board). As is known a MCPCB comprises a layered structure composed of a metal core base, typically aluminum, a thermally conducting/electrically insulating dielectric layer and a copper circuit layer for electrically connecting electrical components in a desired circuit configuration. The metal core base of the MCPCB  160  is mounted in thermal communication with the upper surface of the base  40 , e.g., with the aid of a thermally conducting compound such as for example a material containing a standard heat sink compound containing beryllium oxide or aluminum nitride. A light reflective mask can be provided overlaying the MCPCB that includes apertures corresponding to each LED  110  to maximize light emission from the lamp. 
     Each solid-state light emitter  110  can comprise a gallium nitride-based blue light emitting LED operable to generate blue light with a dominant wavelength of 455 nm-465 nm. The LEDs  110  can be configured as an array, e.g., in a linear array and/or oriented such that their principle emission axis is parallel with the projection axis of the lamp. 
     The wavelength conversion layer  20  of lamp  50  includes one or more photoluminescence materials. In some embodiments, the photoluminescence materials comprise phosphors. For the purposes of illustration only, the following description is made with reference to photoluminescence materials embodied specifically as phosphor materials. However, the invention is applicable to any type of photoluminescence material, such as either phosphor materials or quantum dots. A quantum dot is a portion of matter (e.g. semiconductor) whose excitons are confined in all three spatial dimensions that may be excited by radiation energy to emit light of a particular wavelength or range of wavelengths. 
     The one or more phosphor materials can include an inorganic or organic phosphor such as for example silicate-based phosphor of a general composition A 3 Si(O,D) 5  or A 2 Si(O,D) 4  in which Si is silicon, O is oxygen, A includes strontium (Sr), barium (Ba), magnesium (Mg) or calcium (Ca) and D includes chlorine (Cl), fluorine (F), nitrogen (N) or sulfur (S). Examples of silicate-based phosphors are disclosed in U.S. Pat. No. 7,575,697 B2 “Silicate-based green phosphors”, U.S. Pat. No. 7,601,276 B2 “Two phase silicate-based yellow phosphors”, U.S. Pat. No. 7,655,156 B2 “Silicate-based orange phosphors” and U.S. Pat. No. 7,311,858 B2 “Silicate-based yellow-green phosphors”. The phosphor can also include an aluminate-based material such as is taught in co-pending patent application US2006/0158090 A1 “Novel aluminate-based green phosphors” and patent U.S. Pat. No. 7,390,437 B2 “Aluminate-based blue phosphors”, an aluminum-silicate phosphor as taught in co-pending application US2008/0111472 A1 “Aluminum-silicate orange-red phosphor” or a nitride-based red phosphor material such as is taught in co-pending United States patent application US2009/0283721 A1 “Nitride-based red phosphors” and International patent application WO2010/074963 A1 “Nitride-based red-emitting in RGB (red-green-blue) lighting systems”. It will be appreciated that the phosphor material is not limited to the examples described and can include any phosphor material including nitride and/or sulfate phosphor materials, oxy-nitrides and oxy-sulfate phosphors or garnet materials (YAG). 
     Quantum dots can comprise different materials, for example cadmium selenide (CdSe). The color of light generated by a quantum dot is enabled by the quantum confinement effect associated with the nano-crystal structure of the quantum dots. The energy level of each quantum dot relates directly to the size of the quantum dot. For example, the larger quantum dots, such as red quantum dots, can absorb and emit photons having a relatively lower energy (i.e. a relatively longer wavelength). On the other hand, orange quantum dots, which are smaller in size can absorb and emit photons of a relatively higher energy (shorter wavelength). Additionally, daylight panels are envisioned that use cadmium free quantum dots and rare earth (RE) doped oxide colloidal phosphor nano-particles, in order to avoid the toxicity of the cadmium in the quantum dots. 
     Examples of suitable quantum dots include: CdZnSeS (cadmium zinc selenium sulfide), Cd x Zn 1-x  Se (cadmium zinc selenide), CdSe x S 1-x  (cadmim selenium sulfide), CdTe (cadmium telluride), CdTe x S 1-x  (cadmium tellurium sulfide), InP (indium phosphide), In x Ga 1-x  P (indium gallium phosphide), InAs (indium arsenide), CuInS 2  (copper indium sulfide), CuInSe 2  (copper indium selenide), CuInS x Se 2-x  (copper indium sulfur selenide), CuIn x Ga 1-x  S 2  (copper indium gallium sulfide), CuIn x Ga 1-x Se 2  (copper indium gallium selenide), CuIn x Al 1-x  Se 2  (copper indium aluminum selenide), CuGaS 2  (copper gallium sulfide) and CuInS 2x ZnS 1-x  (copper indium selenium zinc selenide). 
     The quantum dots material can comprise core/shell nano-crystals containing different materials in an onion-like structure. For example, the above described exemplary materials can be used as the core materials for the core/shell nano-crystals. The optical properties of the core nano-crystals in one material can be altered by growing an epitaxial-type shell of another material. Depending on the requirements, the core/shell nano-crystals can have a single shell or multiple shells. The shell materials can be chosen based on the band gap engineering. For example, the shell materials can have a band gap larger than the core materials so that the shell of the nano-crystals can separate the surface of the optically active core from its surrounding medium. In the case of the cadmiun-based quantum dots, e.g. CdSe quantum dots, the core/shell quantum dots can be synthesized using the formula of CdSe/ZnS, CdSe/CdS, CdSe/ZnSe, CdSe/CdS/ZnS, or CdSe/ZnSe/ZnS. Similarly, for CuInS 2  quantum dots, the core/shell nanocrystals can be synthesized using the formula of CuInS 2 /ZnS, CuInS 2 /CdS, CuInS 2 /CuGaS 2 , CuInS 2 /CuGaS 2 /ZnS and so on. 
     The optical component  22  can be configured to include light diffusive (scattering) material. Example of light diffusive materials include particles of Zinc Oxide (ZnO), titanium dioxide (TiO 2 ), barium sulfate (BaSO 4 ), magnesium oxide (MgO), silicon dioxide (SiO 2 ) or aluminum oxide (Al 2 O 3 ). A description of scattering particles that can be used in conjunction with the present invention is provided in U.S. Provisional Application No. 61/793,830, filed on Mar. 14, 2013, entitled “DIFFUSER COMPONENT HAVING SCATTERING PARTICLES”, which is hereby incorporated by reference in its entirety. 
     The reflector portion  25  can comprise a light reflective material, e.g., an injection molded part composed of a light reflective plastics material. Alternatively the reflector can comprise a metallic component or a component with a metallization surface. 
     In operation, the LEDs  110  generate blue excitation light a portion of which excite the photoluminescence material within the wavelength conversion layer  20  which in response generates by a process of photoluminescence light of another wavelength (color) typically yellow, yellow/green, orange, red or a combination thereof. The portion of blue LED generated light combined with the photoluminescence material generated light gives the lamp an emission product that is white in color. 
       FIG. 6  is a schematic partial sectional view of an integrated component  10  intended for a reflector lamp, e.g., such as an MR 16  lamp. In this embodiment the photoluminescence wavelength conversion portion  20  comprises dome-shape in the center of the component. The reflector portion  25  comprises a light reflective material on its inner surface. The wavelength conversion portion  20  of the component  10  is located at or near the focal point of reflector portion  25 . An optical component portion  22  is disposed at the projecting end of the component  10 . The optical component portion  22  may be configured as a lens in some embodiments. The optical component portion  22  may be configured to include light diffusive materials. 
     The interior of the component  10  may include a solid fill material. In some embodiments, the solid fill material has a matching index of refraction to the material of the wavelength conversion portion  20 . In some embodiments, the same base material is used to manufacture both the wavelength conversion portion  20  and the solid fill, with the exception that the solid fill does not include photoluminescence materials. 
       FIG. 7  illustrates that the component  10  can have a generally frusto-conical shape.  FIG. 8  illustrates that the reflector portion  25  of the component may include multi-faceted reflector configuration within the interior surface of the component.  FIG. 9  shows a reflector lamp product that includes the integrated component, e.g., such as an MR 16  lamp product. The lamp product includes one or more LEDs  110  and an electrical connector  180 . 
     In embodiments where the integrated component has a constant cross section, it can be readily manufactured using an extrusion method. Some or all of the integrated component can be formed using a light transmissive thermoplastics (thermosoftening) material such as polycarbonate, acrylic or a low temperature glass using a hot extrusion process. Alternatively some or all of the component can comprise a thermosetting or UV curable material such as a silicone or epoxy material and be formed using a cold extrusion method. A benefit of extrusion is that it is relatively inexpensive method of manufacture. It is noted that the integrated component can be co-extruded in some embodiments even if it includes a non-constant cross-section. 
     A co-extrusion approach can be employed to manufacture the integrated component. Each of the reflector  25 , wavelength conversion  20 , and optical  22  portions are co-extruded using respective materials appropriate for that portion of the integrated component. For example, the wavelength conversion portion  20  is extruded using a base material having photoluminescence materials embedded therein. The reflector portion  25  can be co-extruded such that is entirely manufactured with light reflective plastics, and/or where only the interface between the reflector portion  25  and the wavelength conversion portion  20  is co-extruded with the light reflective plastics and the rest of the reflector portion  25  is extruded using other appropriate materials. The optical component portion  22  can be co-extruded using any suitable material, e.g., a light transmissive thermoplastics by itself or thermoplastics that includes light diffusive materials embedded therein. 
     Alternatively, some or all of the component can be formed by injection molding though such a method tends to be more expensive than extrusion. If the component has a constant cross section, it can be formed using injection molding without the need to use an expensive collapsible former. In other embodiments the component can be formed by casting. 
     In some embodiments, some or all of the different reflector  25 , wavelength conversion  20 , and optical  22  portions of the integrated component are manufactured with base materials having matching indices of refraction. This approach tends to reduce light losses at the interfaces between the different portions, increasing the emission efficiencies of the overall lighting product. 
     It will be appreciated that the invention is not limited to the exemplary embodiments described and that variations can be made within the scope of the invention.