Ceramic wavelength conversion plates and light sources with the same

Abstract

Wavelength conversion plate comprising: a plurality of converters (110), each converter comprising a ceramic material capable of converting incident primary light into secondary light, and each converter comprising a different material or having a different activator concentration, and the converters having a shape of nested concentric cylinders; a reflector (111) coupled to at least one of the plurality of converters, the reflector comprising a ceramic material capable of reflecting secondary light emitted by the converters, and the reflector material being different from the converter materials; and an interface (112) between at least one of the plurality of converters and the reflector, wherein the reflector surrounds an outer edge of the at least one converter, and wherein the reflector material is in contact with over at least about 50% of the interface.

Description

AREA

[0001] The present disclosure relates generally to semiconductor light sources such as light-emitting diodes (LEDs), and more particularly to LED light sources having one or more ceramic wavelength conversion plates. BACKGROUND

[0002] LED chips can produce visible or non-visible light within a specific region of the light spectrum. For example, the light emitted from the LED can be light in the blue, red, green, non-visible ultraviolet (UV), and / or near-UV spectral range, depending on the LED's material composition. If it is desired to construct an LED light source that produces a color different from the LED's output color, it is known to convert light emitted from the LED at a first wavelength or range of wavelengths (the "primary light" or "excitation light") into light at a second wavelength or range of wavelengths (the "secondary light" or "emission light") using photoluminescence.

[0003] Photoluminescence generally involves absorbing higher-energy primary light with a wavelength-conversion material, such as a phosphor or mixture of phosphors. The absorption of the primary light can excite the wavelength-conversion material to a higher energy state. When the wavelength-conversion material returns to a lower energy state, it emits secondary light, generally at a different wavelength / wavelength range than the primary light. The wavelength / wavelength range of the secondary light can depend on the type of wavelength-conversion material used. In principle, secondary light with a desired wavelength / wavelength range can be achieved by appropriate selection of the wavelength-conversion material.This process can be understood as "wavelength downconversion," and an LED combined with a wavelength conversion structure including a wavelength conversion material such as a phosphor to generate secondary light can be described as a "phosphor-converted LED" or "wavelength-converted LED."

[0004] In one known configuration, an LED chip, such as a III-nitride chip, is positioned within a reflector cup package and a bulk, and a conformal layer or thin film of or including a wavelength conversion material is deposited directly on the surface of the chip. In another known configuration, the wavelength conversion material may be provided in a solid, self-supporting flat structure, such as a ceramic plate, a single-crystal plate, or a thin-film structure. Such a plate may be referred to herein as a "wavelength conversion plate." The plate may be attached directly to the LED, e.g., by wafer bonding, sintering, gluing, etc. The configuration may be referred to as "chip-level conversion" or "CLC." Alternatively, the plate may be positioned remotely from the LED by an intermediary element. Such a configuration may be referred to as "remote conversion."

[0005] Depending on the desired far-field pattern of the light output from any chip-plus-converter configuration, one drawback associated with wavelength conversion plates is that a certain amount of light may escape through the sides of the converter during the conversion process (side emission). Side emission can result in reduced efficiency and / or angularly inhomogeneous light distribution. Heat generated during any conversion process can also reduce the efficiency of the system, particularly in cases where a wavelength conversion plate is used in high-brightness / power applications.

[0006] In some applications, the side emission problem has been addressed by casting a ceramic within a silicon layer around the sides of the conversion plate. For example, a TiO2-silicone casting can be formed by mixing TiO2 powder into silicon and then disposing the resulting material around an LED chip and a wavelength conversion plate. The silicon in the casting material can then be cured to create a solid reflective layer around the emission surface of the wavelength conversion plate. Consequently, only the top surface of the wavelength conversion plate can be exposed for light emission. Light emitted toward the side of the conversion material is reflected by the reflective material.

[0007] While this solution can effectively address side emission, it requires layers of ceramic-in-silicone to be individually cast around the wavelength conversion plate used in each lamp component. This can contribute to the complexity of the lamp manufacturing process. Furthermore, the ceramic-in-silicone material can be overfilled during casting, causing it to cover a portion of the wavelength conversion plate's top surface and potentially reducing light output. The ceramic-in-silicone material, on the other hand, can be underfilled during casting, leaving areas where side emission from the wavelength conversion plate is still possible.

[0008] In addition to the optical issues mentioned above, the use of ceramic materials in silicone can also impose limitations on the thermal management of the system in which it is integrated. For example, in systems where a significant amount of heat is generated (e.g., high-power / brightness applications), thermal breakdown of the silicone (or other organic material) in the reflective layer may occur. Furthermore, because the silicone (or other organic material) in the mold has low thermal conductivity, it may not be able to adequately conduct heat away from the LED component and / or the wavelength conversion plate, which can lead to overheating.

[0009] Furthermore, a “remote phosphor” system is known from US 2010 / 0 301 360 A1, in which phosphor layers are physically separated from the light source and reflective elements.

[0010] Furthermore, DE 11 2006 000 694 B4 discloses a housing construction for light-emitting devices in which ceramic and metallic materials are combined. SUMMARY

[0011] The invention is set out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Reference should be made to the following detailed description, which should be read in conjunction with the following figures, in which like characters represent like parts: Fig. 1A to 1C schematically illustrate, in cross-section, exemplary wavelength conversion plates consistent with the present disclosure; Fig. 2 schematically illustrates a top view of an exemplary wavelength conversion plate having multiple converters consistent with the present disclosure. Fig. 3A to 3C schematically illustrate plan views of additional exemplary wavelength conversion plates according to the present disclosure. Fig. 4A and Fig. 4B schematically illustrate in cross-section exemplary devices including a wavelength conversion plate consistent with the present disclosure; and Fig. 5 schematically illustrates a light-activated remote phosphor system with a wavelength conversion plate consistent with the present disclosure.

[0013] For a thorough understanding of the present disclosure, reference should be made to the following detailed description, including the appended claims, taken in conjunction with the above-described drawings. Although the present disclosure is described in connection with exemplary embodiments, the disclosure is not intended to be limited to the specific forms set forth herein. It should be understood that many omissions and substitutions of equivalents are contemplated as circumstances may suggest or make appropriate. It should also be understood that the phraseology and terminology employed herein are for the purpose of description and should not be considered limiting unless otherwise expressly stated. DETAILED DESCRIPTION

[0014] As used herein, the term “about,” when used in connection with a numerical value or range of values, means + / - 5% of the stated numerical value or range.

[0015] From time to time, one or more aspects of the present disclosure may be described using a numerical range. Unless otherwise stated herein, any stated range should be interpreted as encompassing any iterative values ​​between stated endpoints, as if such iterative values ​​were expressly stated. Such ranges should also be interpreted as encompassing any and all ranges falling within or between such iterative values ​​and / or stated endpoints, as if such ranges were expressly stated herein.

[0016] References to the color of a phosphor, LED, or conversion material generally refer to its emission color unless otherwise stated. Thus, a blue LED emits blue light, a yellow phosphor emits yellow light, and so on.

[0017] One aspect of the present disclosure relates to wavelength conversion plates comprising a ceramic conversion material and a ceramic reflective material. As discussed in detail below, such wavelength conversion plates may provide one or more advantages over existing wavelength conversion plates that use ceramic in silicon (or another organic material) as the reflective material to address side emission.

[0018] In this respect, Fig. 1A to 1C, which illustrate non-limiting examples of wavelength conversion plates according to the present disclosure. As shown in each figure, a wavelength conversion plate 100 includes a converter 101 and a reflector 102.

[0019] The converter 101 may be made of any ceramic material capable of converting primary light into secondary light (hereinafter referred to as a "conversion material"). In particular, the converter 101 may comprise one or more conversion materials to achieve a desired wavelength conversion, including, but not limited to, yellow phosphor, green phosphor, red phosphor, and / or combinations thereof. Non-limiting examples of conversion materials include oxyfluorates, nitrides (including oxynitride phosphors), and oxide phosphors (e.g., aluminate garnets, silicates, etc.), including those containing cerium, gadolinium, gallium, scandium, europium, and / or other elements.In some embodiments, the reaction materials are selected from cerium-activated yttrium aluminum garnets (YAG:Ce), cerium-activated yttrium gadolinium aluminum garnets (YGdAG:Ce), cerium-activated lutetium aluminum garnets (LuAG:Ce), cerium-activated lutetium gallium aluminum garnets (LuGAG:Ce), europium- or cerium-activated alkaline earth (AE) silicon oxynitride (AE-SiON:Eu, where AE denotes at least one element selected from Ba, Sr, and Ca), europium- or cerium-activated metal SiAlON (M-SiAlON, where M is selected from alkali ions, rare earth ions, alkaline earth ions, Y, Sc, and combinations thereof), and the like. Doping elements such as, for example, Elements such as cerium or europium can be understood as “activators” of the reaction material (i.e. the elements largely responsible for light absorption and light emission in the reaction material) and are referred to as such in this application.In one non-limiting embodiment, the converter 101 is made of (Y. 2,94 Ce 0,06 )Al5O 12 , (Y 2,94 Ce 0,006 Gd 0,45 ) Al5O 12 , (Lu 2,97 Ce 0,03 ) A1 s O 12 , combinations thereof, and the like. Such materials may be arranged in a desired distribution and / or pattern within the converter 101.

[0020] In non-limiting preferred embodiments, the converter 101 is formed entirely of ceramic material, i.e., the converter 101 does not include any non-ceramic materials. In other words, the converter 101 may be made of, or consist essentially of, ceramic material, such as, but not limited to, the previously identified ceramic materials.

[0021] The reflector 102 may be formed of any ceramic material with suitable optical and / or thermal properties, such as high reflectivity (particularly for secondary light), desirable thermal conductivity, and / or high-temperature resistance. For convenience, such materials are referred to herein as "reflective materials." Non-limiting examples of reflective materials that may be used to form the reflector 102 include ceramics such as aluminum oxide (Al2O3), yttrium, lutetium, and other aluminum garnets (YAG, LuAG, etc.), titanium dioxide (TiO2), barium aluminate (BaAl2O4), yttrium oxide (Y2O3), zirconium oxide (ZrO2), aluminum nitride (AlN), combinations thereof, and the like. In some embodiments, the reflective material is Al2O3.

[0022] The reflective materials, when sintered, may have a reflectance in the range of greater than or equal to about 80%, such as greater than or equal to about 85%, greater than or equal to about 90%, greater than or equal to 95%, or even greater than or equal to 99%. Preferably, the reflector 102 has a reflectance within the aforementioned values / ranges for the secondary light emitted by the converter 101. In some embodiments, the reflector 102 is formed entirely or partially from materials that are transparent to primary light but reflective to secondary light. Such materials can be used to form a dichroic filter in which a narrow range of wavelengths defines a boundary between the transmission above and the reflection below, or vice versa.

[0023] In non-limiting preferred embodiments, the reflector 102 is formed entirely of ceramic material, i.e., the reflector 102 does not include any non-ceramic materials. In other words, the reflector 102 may be made of, or consist essentially of, ceramic material, such as, but is not limited to, the previously identified ceramic materials.

[0024] Fig. 1A illustrates an exemplary configuration of a wavelength conversion plate 100 in which the converter 101 is disposed within a through-hole 103 in the reflector 102. Although the through-hole 103 is illustrated as having a platelet (e.g., a substantially circular shape), it should be understood that the through-hole 103 may have any geometric or irregular shape. For example, the through-hole 103 may be in the shape of a circle, an oval, a square, a rectangle, a triangle, etc. In some embodiments, the through-hole 103 has a size and shape that substantially correspond to the size and shape of an LED package with which the wavelength conversion plate 100 may be used. The converter 101 is coupled to the reflector 102 at least partially through its interaction with the surface of the through-hole 103, which forms the interface between the converter 101 and the reflector 102. As in Fig. 1A, the reflector 102 preferably abuts the converter 101 over the entire interface between the reflector 102 and the converter 101.

[0025] The converter 101 may be machined or otherwise configured to fit within the through-hole 103. In such embodiments, the position of the converter 101 within the through-hole 103 may be maintained by mechanical compression between the edges of the converter 101 and adjacent portions of the reflector 102. Alternatively or additionally, the position of the converter 101 may be maintained by a physical and / or chemical bond between the edges of the converter 101 and adjacent portions of the reflector 102.

[0026] Although not required, a layer of adhesive or other bonding material may also be used to maintain the position of the converter 101 within the through-hole 103. Preferably, no such adhesive or bonding material is used. However, if used, such an adhesive or bonding material may transmit more than or equal to 80%, about 85%, about 90%, or even about 95% of the primary and / or secondary light in the system. Alternatively or additionally, such an adhesive or bonding material may reflect more than or equal to about 80%, about 85%, about 90%, or even about 95% of the primary and / or secondary light in the system. The adhesive or bonding material, if used, may further be selected to have high thermal conductivity. In such embodiments, all or a portion of the inner edges of the through-hole 103 may be in direct contact with the outer edges of the converter 101.

[0027] Fig. 1B illustrates an alternative exemplary configuration of a wavelength conversion plate according to the present disclosure. In this case, the reflector 102 includes a recess 104 in a surface thereof. In some embodiments, the recess 104 may be a region of the reflector 102 having a thickness less than the maximum thickness of the reflector 102. However, a region of reduced thickness is not required. The recess 104 may be formed, for example, by laminating or otherwise coupling the reflector 102 containing a through-hole to another material. In any event, the recess 104 may be formed using a wide variety of processes, such as stamping, embossing, coining, etching, abrading, cutting, etc., of a raw article and / or precursor containing the reflective material prior to fusing the article / precursor, e.g.,formed by sintering or another thermal process.

[0028] The recess 104 is in Fig. 1B as having a generally U-shaped cross-section. Of course, the recess 104 may have any desired shape or configuration. For example, the recess 104 may have a rectangular, circular, oval, oblong, triangular, trapezoidal, pentagonal, and / or irregular shape. In some embodiments, the recess 104 is sized and shaped to substantially conform to the size and shape of an LED package with which the wavelength conversion plate may be used. As shown in Fig. 1B, the recess 104 is a rectangular cuboid, with the surfaces of the sides and bottom forming the interface with the converter 101.

[0029] How the implementation material in Fig. 1A, the converter 101 can be Fig. 1B may be machined or otherwise configured to fit within the recess 104 of the reflector 102, e.g., as an insert. In such cases, the position of the converter 101 within the recess 104 may be maintained by mechanical compression between the edges of the converter 101 and portions of the reflector 102 that form walls 105 of the recess 104. Alternatively or additionally, the position of the converter 101 within the recess 104 may be maintained by a physical and / or chemical bond between the converter 101 and adjacent portions of the reflector 102.

[0030] As in the Fig. 1A, a layer of adhesive or bonding agent may also be used to maintain the position of the converter 101 within the recess 104, although the use of such an agent is not required. Preferably, no such adhesive or bonding agent is used. However, if used, such an adhesive or bonding agent may have high thermal conductivity and may transmit more than or equal to 80%, about 85%, about 90%, or even about 95% of the primary and / or secondary light. Alternatively or additionally, such an adhesive or bonding agent may reflect more than or equal to about 80%, about 85%, about 90%, or even about 95% of the primary and / or secondary light in the system. In such embodiments, all or a portion of the inner surfaces of the walls of the recess 104 may be in direct contact with corresponding outer edges of the converter 101.

[0031] The recess 104 in Fig. 1B was discussed and illustrated above as being entirely defined by a single reflector 102. However, it should be understood that various materials may be used to form the lower portion or side of the recess 104. As shown in Fig. 1C, the reflector 102 may, for example, be divided into two parts 102' and 102". A first ceramic material may be used in the upper part 102' to form the sides of the recess 104, and a second ceramic material may be used in the lower part 102" to form the lower portion of the recess 104. The first and second ceramic materials may be the same or different. For example, the first material may comprise one or more reflective materials, such as the ceramics discussed above in connection with the reflective material 102, whereas the second material may comprise a different ceramic material.

[0032] Therefore, in some embodiments, a recess may be formed by punching (or drilling) a through-hole in an upper reflector portion 102' and laminating the punched reflective material to another material layer forming the lower reflector portion 102". In such embodiments, the recess 104 would be defined by the sides of the through-hole in the upper reflector portion 102' and a surface of the other material layer forming the lower reflector portion 102". The other material layer may comprise a ceramic material that is the same as or different from the ceramic material used to form the upper reflector portion 102'. Alternatively or additionally, the other material layer of the lower reflector portion 102" may be formed by one or more layers of metallic and / or dielectric materials.

[0033] In any case, the material forming the lower reflector portion 102" may be configured to transmit primary light (e.g., emitted by an LED) and reflect secondary light emitted by the converter 101. That is, the lower reflector portion 102" may be configured to transmit more than about 80% of the incident primary light (such as more than or equal to about 85%, about 90%, about 95%, about 99%, or even 100% of the incident primary light) while reflecting more than or equal to about 80% of the secondary light emitted by the converter 101 (such as more than or equal to about 85%, about 90%, about 95%, about 99%, or even about 100% of the secondary light). In this regard, a portion of the lower reflector member 102" may be configured as a dichroic filter, a thin film filter, a thin film metal reflector, an interference filter, and the like.

[0034] Although the above disclosure has focused on wavelength conversion plates comprising a single conversion material, multiple conversion materials may be used. In this regard, reference is made to Fig. 2, which illustrates an exemplary wavelength conversion plate 200 including a plurality of converters 201, 201', 201" disposed in through-holes / recesses 203, 203', 203" in the reflective material 202. In each case, the reflector 202 surrounds the outer edges of the converters 201, 201', 201". The conversion materials 201, 201', 201" may be formed of the same or a different ceramic material, such as the exemplary ceramics noted above with respect to the converter 101. In some embodiments, the conversion materials 201, 201', 201" are formed from different materials that emit secondary light in different regions of the electromagnetic spectrum. For example, the conversion materials 201, 201' and 201" may be configured to emit secondary light in the white (e.g., YGdAG:Ce), green (LuAG:Ce), and yellow (YAG:Ce) regions of the visible spectrum, respectively.Likewise, reflector 202 may comprise one or more of the ceramic materials noted above with respect to reflector 102. In some embodiments, reflector 202 is YAG.

[0035] As can be appreciated, the wavelength conversion plate 200 can be used as a color wheel in a light engine, such as an LED light engine. As used herein, the term LED light engine means a set of LED chips mounted on a common substrate to form a unified light source. That is, it can be used to provide selective conversion of primary light into secondary light at a desired wavelength, e.g., by rotating the plate such that the primary light is incident on one or more of the converters 201, 201', and / or 201".

[0036] Fig. 3A-3C illustrate additional exemplary wavelength conversion plates according to the present disclosure. As shown in each of these figures, the wavelength conversion plates 300 may include multiple regions of conversion material. For clarity, such regions are Fig. 3A-3C as region 301, 301', 301'', 301''', etc. As further illustrated, each region may contain a reaction material that is of the same or a different type as an adjacent region and that may have the same or a different activator concentration as an adjacent region. In Fig. For example, in FIG. 3A, region 301 is YAG:Ce containing 2 at.% Ce as activator, region 301' is YAG:Ce containing 1.5 at.% Ce as activator, region 301'' is YAG:Ce containing 1.0 at.% Ce as activator, and region 301''' is YAG:Ce containing 0.5 at.% Ce as activator. Fig. 3B illustrates a wavelength conversion plate in which region 301 is LuAG:Ce containing 1.0 atom% Ce as activator, region 301' is YAG:Ce containing 1.0 atom% Ce as activator, region 301'' is LuAG:Ce containing 0.5 atom% Ce as activator, and region 301''' is YAG:Ce containing 0.5 atom% Ce as activator. And in Fig. 3C, region 301 is LuAG:Ce, which contains 1.0 atom% Ce as activator, and region 301' is YAG:Ce, which contains 1.0 atom% Ce as activator. In each of Fig. 3A-3C, the regions of the conversion material may be surrounded by a reflective material 302, shown for illustrative purposes as Al2O3.

[0037] As from Fig. 3A-3C, the wavelength conversion plates of the present disclosure may comprise a converter in which the composition of one or more ceramic materials varies relative to a fixed position in the converter plate. For example, the converter plates described herein may be configured such that the composition of the ceramic conversion material changes periodically or gradually in terms of activator concentration, activator type, and / or other chemical (elemental) constituents over a defined range. As shown in Fig. As shown in Figure 3A, the activator concentration in a ceramic conversion material may gradually decrease from the center of the converter or vice versa. In other words, a gradient of the conversion material concentration may be set relative to the center of the wavelength conversion plate 300. Alternatively or additionally, the type of conversion material may vary with location, as shown in Fig. 3B and Fig. 3C shown.

[0038] Although Fig. 3A-3C illustrate embodiments in which regions of the conversion material take the form of concentric rings or cylinders with more or less the same width, other configurations are also possible. For example, regions 301, 301', etc., may be configured to have the same or a different width as an adjacent region. Wavelength conversion plates with fewer or more regions of conversion material than those in Fig. 3A-3C are also possible. Indeed, wavelength conversion plates having from about 1 to about 100 regions, such as from about 2 to about 50, from about 2 to about 20, from about 2 to about 10, or even from about 2 to about 5 regions of conversion material are contemplated by the present disclosure.

[0039] Likewise, the Fig. The activator concentrations indicated in Figures 3A-3C are considered exemplary only. The concentration of each range can be tailored, e.g., to provide a desired level of conversion and / or to provide other desired properties, such as spectral color, level of light scattering, and the like. In some embodiments, the activator concentration can range from greater than 0 to about 5 atomic percent or more, such as greater than 0 to about 2.5 atomic percent, about 0.5 to about 2 atomic percent, or even about 0.5 to about 1 atomic percent.

[0040] In addition, the Fig. 3A-3C are considered only as examples. Regions 301, 301', etc., may be formed from any of the conversion materials specified herein, including those specified above for conversion material 101. Likewise, reflective material 302 may be formed from any of the reflective materials described herein, including those specified above for the reflective material.

[0041] As can be seen from the above, the present disclosure contemplates wavelength conversion plates that eliminate the need for embedding the converter plate in reflective silicone. Because the ceramics used in the reflective material can be highly thermally conductive and resistant to degradation, the wavelength conversion plates described herein may be suitable for high-brightness / power applications that may not be possible using silicone reflectors. Furthermore, the reflector used in the wavelength conversion plates described herein may have high thermal conductivity, which can improve thermal management by providing alternative mechanisms for dissipating heat.

[0042] For example, in cases where the reflector 102 is made of a ceramic, the reflector may have a thermal conductivity equal to or approaching the thermal conductivity of the corresponding bulk ceramic. In some embodiments, the reflectors described herein have a thermal conductivity in the range of about 25% or more, such as about 50% or more, about 85% or more, about 95% or more, or even about 99% or more of the thermal conductivity of the corresponding bulk ceramic. In some embodiments, the thermal conductivity of the reflectors described herein is equal to the thermal conductivity of the corresponding bulk ceramic.Considering this, bulk alumina (Al2O3) has a thermal conductivity of about 25 to 45 W / mK (watts per meter-Kelvin), yttrium aluminum garnet (YAG) has a bulk thermal conductivity of about 13 W / mK, zirconium oxide (ZrO2) has a bulk thermal conductivity of about 1 to 2 W / mK, aluminum nitride (AlN) has a bulk thermal conductivity of about 70-120 W / mK, and titanium oxide (TiO2) has a bulk thermal conductivity of about 11-13 W / mK.

[0043] In other words, the reflectors described herein may have a thermal conductivity in the range of about 5 to about 35 W / mK, such as about 8 to about 30 W / mK, about 11 to about 25 W / mK, or even about 12 to about 20 W / mK. Reflectors having thermal conductivities falling within, above, or below such ranges may, of course, be used and are contemplated herein.

[0044] In contrast, when ceramic powders are dispersed in silicone, the resulting material can have a thermal conductivity of less than 1 W / mK or even less than about 0.5 W / mK. In this regard, the thermal conductivity of a material with ceramic in silicone can be estimated from the thermal conductivity and density of the matrix (silicone) and the filler (e.g., ceramic particles), as well as the filler loading. For example, ceramics such as YAG can have a thermal conductivity of over about 13 W / mK and a density of about 4 g / cm 3 The silicone matrix may have a thermal conductivity of about 0.17 W / mK and a density of about 1.0 g / cm 3 Based on these factors, the calculated thermal conductivity of a YAG / silicone reflector can range from 0.15 W / mK (0 wt% YAG particles) to approximately 0.375 W / mK (60 wt% YAG particles).

[0045] Consequently, the reflectors according to the present disclosure can have a thermal conductivity significantly higher than that of a ceramic in silicone. In fact, the reflectors described herein can have a thermal conductivity greater than or equal to about 1.5-100 times the thermal conductivity of a corresponding ceramic in silicone, such as about 5 to about 95, about 10 to about 90, about 15 to about 75, about 20 to about 65, or even about 25 to about 50 times the thermal conductivity of a corresponding ceramic in silicone. As used herein, the term "corresponding ceramic in silicone" means a ceramic in silicone that contains ceramic particles having the same composition as the ceramic(s) used to form the reflectors described herein.

[0046] The reflectors described herein may also exhibit a desirable temperature resistance. That is, the reflectors described herein may be capable of operating at temperatures ranging from approximately -40°C to approximately 300°C. As can be seen, the maximum operating temperature of the lighting devices described herein may exceed the temperature at which the matrix of a ceramic would decompose into silicone.

[0047] The wavelength conversion plates described herein may also enable the fabrication of conversion plates designed or otherwise formulated to provide desired optical properties in a specific environment. As described in Fig. 3A-3C, the wavelength conversion plates described herein may comprise multiple regions of conversion material. Each region may be formulated to provide a desired performance in the optical environment in which it is disposed. The regions may be formed as multiple nested concentric cylinders, as shown in Fig. 3A-3C. The reaction materials of each region can consist of a different reaction material or have a different activator concentration. The reaction materials of Fig. 3A, for example, each have a different Ce activator concentration and are arranged such that the Ce concentration progressively decreases from the innermost region 301 to the outermost region 301'''.

[0048] In cases where the wavelength conversion plate is to be used in conjunction with a light source that produces excitation light in a focused beam with high optical density, incident on a specific region of the wavelength conversion plate 300, e.g., region 301. In such cases, region 301 can be formulated to include desired conversion materials at an appropriate concentration to provide a desired level of conversion to secondary light.

[0049] An example of the use of conversion materials with multiple conversion levels is the control of color as a function of the angle of two-dimensional conversion surfaces. Primary light can be emitted directionally from an LED source and can therefore traverse the conversion material layer at angles other than perpendicular (i.e., other than perpendicular to the two-dimensional plane of the conversion material layer). Primary light traversing at a high angle can be more strongly absorbed and converted to secondary light. By tailoring the activator content of the conversion plate to match the incident angle of the primary light emitted by a light source, a desired level of primary-to-secondary light conversion can be achieved.

[0050] Additionally, color rings or bands can appear in the far field of an illumination system. The conversion plates described here can address or modify this effect by influencing the probability of primary light absorption in outer, larger-angle directions. This can give primary light impinging on these areas the same or a similar probability of absorption or transmission as primary light with an inner, smaller-angle direction traversing the conversion material.

[0051] The wavelength conversion plates of the present disclosure may be manufactured using a variety of methods. For example, the wavelength conversion plates may be manufactured by spin coating, slip or tape casting, injection molding, extrusion, or another deposition technique to form a green (i.e., "unsintered") conversion plate with a desired configuration. In some embodiments, one or a combination of such methods may be used to produce a green conversion plate with the configuration described in Fig. 1A-1C and / or 2, wherein a conversion material is disposed within a through-hole or recess of a reflective material. Alternatively or additionally, such methods could be used to form a raw conversion plate having the configuration shown in Fig. 3A-3C, wherein rings or other periodic structures containing conversion material are formed and surrounded by a raw reflective material.

[0052] Once formed, the green conversion plate can be thermally processed, e.g., via sintering, to produce a wavelength conversion plate in which the ceramic conversion materials and ceramic reflection materials individually or jointly achieve a complete or substantially complete density. "Complete density" is used herein to refer to the density of the bulk material having the same composition. Substantially complete density means greater than or equal to about 92% complete density, such as about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, or even about 99% complete density.Thus, for example, if a raw wavelength conversion plate comprises YAG:Ce as the ceramic conversion material, sintering or otherwise heat-treating the raw wavelength conversion plate to full density means treating the plate such that the density of the YAG:Ce in the sintered article approaches the density of the bulk YAG:Ce.

[0053] In some embodiments, sintering or other heat processing may cause the ceramic conversion and reflection materials to melt, diffuse, or otherwise coalesce at their respective interfaces. Likewise, such processing may cause the ceramic conversion and reflection materials to form a boundary, allowing the ceramic conversion material to flow into interstices in the ceramic reflection material, and vice versa.

[0054] The ceramics in the conversion and reflection materials can therefore be bonded together, for example, via mechanical compression, a physical bond, and / or a chemical bond. Alternatively or additionally, the ceramic conversion and reflection materials can form a boundary during sintering or other heat processing, in which the ceramic conversion material is not present within the interstices of the ceramic of the reflection material, and vice versa. In such cases, the ceramic conversion material can only be held in place in a through-hole / recess in the ceramic reflection material by mechanical compression.

[0055] For example, a fully sintered converter can be inserted into a through-hole or recess in a partially sintered ceramic reflector. Heat processing of the reflector / converter combination would cause further sintering and shrinkage of the reflector, resulting in a compressive force being applied to the converter, securing it within the through-hole or recess.

[0056] The temperature at which sintering or heat processing may take place may depend on the ceramic materials used as the conversion material and the reflective material. In some embodiments, green articles containing a ceramic conversion material and ceramic reflective material may be sintered together at a temperature in the range of about 1300°C to about 2000°C, such as about 1400°C to about 1800°C, about 1500°C to about 1750°C, or even about 1600°C to about 1725°C. Sintering temperatures above, below, and between the aforementioned ranges may, of course, also be used and are contemplated by the present disclosure.

[0057] As can be appreciated from the above, sintering or other heat processing of the raw articles described herein can form a wavelength conversion plate made entirely of inorganic materials, i.e., an "all-ceramic" or "composite ceramic" wavelength conversion plate. In such cases, the ceramic conversion material can have a solid rim of ceramic reflective material around its edges, e.g., as in Fig. 1A. In cases where the conversion material is disposed within a recess in the second ceramic ribbon, sintering or other heat processing may result in a ceramic converter plate in which a ceramic reflective material frames the sides and bottom of a ceramic conversion material, e.g., as shown in Fig. 1B shown.

[0058] In both cases, the reflection frame or edge of the wavelength conversion plates described here can exhibit a high degree of backscattering, the type and extent of which can depend on the ceramic material used. For example, in optically isotropic materials such as yttrium aluminum garnet (YAG) and its variants, the scattering of secondary light emitted by the conversion material can result from pores and / or secondary phases in the reflection material. In optically anisotropic materials such as aluminum oxide (Al2O3), the ceramic can contain randomly oriented grains with different refractive indices. Consequently, light can scatter at the grain boundaries of such materials.

[0059] In both cases (optically isotropic or optically anisotropic materials), a property of interest is the scattering length, i.e., the average distance that light must travel within the reflective material before it is scattered. The scattering length can be directly related to the density of scattering materials, their scattering cross section, and / or index anisotropy. To provide a desired optical confinement of the secondary light emitted by the conversion material, the backscattering area of ​​the reflective material can be significantly smaller than the corresponding dimensions of the reflective material. In some embodiments, most of the backscattering of secondary light can occur over a few scattering lengths. In such cases, the scattering length of the reflective material (e.g., the thickness / width of the reflector 102 in Fig. 1A-1C) be less than or equal to approximately one order of magnitude smaller than the lateral dimensions of the conversion material.

[0060] Another aspect of the present disclosure relates to illumination devices comprising at least one of the wavelength conversion plates described herein. Fig. 4A illustrates an exemplary configuration of such an illumination device. As shown, the device 400 includes a light source 404 and a wavelength conversion plate 407 disposed within a housing 408. In this embodiment, the wavelength conversion plate 407 includes a converter 401 disposed within a through-hole 418 in a reflector 402. The bottom surface 420 of the wavelength conversion plate 407 is Fig. 4A as being oriented generally parallel to a light-emitting surface (upwardly facing surface) 422 of the light source 404. However, such orientation is not required, and the light source 404 and the wavelength conversion plate 407 may be oriented in any suitable manner. Although the light source 404 and the wavelength conversion plate 407 are shown as having respective top and bottom surfaces that are smooth, it should be understood that such surfaces may be roughened, textured, etc., depending on the desired optical coupling and extraction.

[0061] The light source 404 may be any light source capable of emitting primary light. Non-limiting examples of such light sources include semiconductor sources such as LEDs (e.g., nitride III-V LEDs such as an InGaN LED) and laser diodes. Preferably, the light source 404 is a blue or UV LED or laser diode. More preferably, the light source 404 is a blue LED or laser diode emitting in a wavelength range of 420 nm to 490 nm, or even more preferably 450 nm to 475 nm. In any case, the light source(s) used in the illumination devices described herein may be coupled to a light guide (e.g., a light pipe) to form a surface emitter. Further, although the device 400 is shown as comprising a single light source 404, it should be understood that the illumination devices described herein may comprise an array of light sources.

[0062] In operation, the light source 404 can emit primary light (indicated by arrows 405) described by a number of parameters, such as a peak or dominant wavelength, color coordinates, intensity, etc. The primary light emitted by the light source 404 can be incident on the bottom surface 420 of the converter 401 of the wavelength conversion plate 407. The converter 401 can absorb the primary light and be excited to a higher energy state. When the excited converter 401 returns to a lower energy state, it can emit secondary light (indicated by arrows 406). In this way, the primary light incident on the converter 401 can be converted into secondary light.

[0063] The converter 401 can be configured to have a desired level of conversion efficiency, i.e., to convert a desired amount of incident primary light into secondary light. In some embodiments, the converter 401 has a conversion efficiency of greater than or equal to 50%, such as about 50 to about 100%, about 60 to about 99%, about 70 to about 98%, about 80 to about 97%, or even about 85 to about 96%. Preferably, the conversion efficiency of the converter 401 is greater than 95%.

[0064] As explained above, reflector 402 can function to reflect incident primary and / or secondary light. Regarding the former, reflector 402 can reflect incident primary light in such a way that it is incident on or passes through converter 401. In this way, reflector 402 can increase the opportunity for converter 401 to absorb primary light and convert it into secondary light, thus increasing conversion efficiency.

[0065] Secondary light emitted by the converter 401 may not always be emitted toward the opening 410 of the housing 408. For example, secondary light may be emitted to either side of the converter 401 (side scatter) or rearward toward the light source 404 (back scatter). If such side scattered and back scattered light is not redirected toward the opening, it may be absorbed or otherwise lost, resulting in a loss of light output from the device 400. In this regard, the reflective material may be configured to have a high reflectivity with respect to the secondary light emitted by the converter 401, as discussed above. In the Fig. For example, in the embodiment shown in Figure 4A, reflector 402 is disposed around the edge(s) of converter 401. Consequently, reflector 402 can reflect laterally scattered secondary light emitted by converter 401, thus increasing the opportunity for such light to escape from device 400. A multilayer interference coating can be applied to the bottom surface 420 of converter plate 407, which would allow primary light 405 to enter converter 401 and reflect secondary light 406 emitted by converter 401 back toward opening 410.

[0066] Fig. Figure 4B illustrates another exemplary lighting device configuration according to the present disclosure. Except for the location of the wavelength conversion plate 407 and the light source 404, the parts of the device 400 in Fig. 4B to the Fig. 4A. Consequently, the nature and function of such common parts will not be repeated. Of course, this illustration is only exemplary, and the light source 404 and the wavelength conversion plate 407 can be oriented in any desired manner.

[0067] In Fig. 4B, the wavelength conversion plate 407 is configured such that the converter 401 is disposed within a recess 416 in the reflector 402. As such, only one surface of the converter 401 is exposed to the light from the light source 404. In this embodiment, the exposed surface 421 of the converter 401 is oriented to face a light-emitting surface 422 of the light source 404. Consequently, the secondary light emitted by the converter 401 can be emitted in a direction other than the direction of the opening 410 of the device 400, e.g., toward the light source 404.

[0068] To address this problem, the device 400 may include a secondary reflector 412, which may be integral with the housing 408 or separate therefrom. Fig. 4A and Fig. 4B, the secondary reflector 412 is integral with the housing 408. Thus, the secondary reflector 412 may, for example, take the form of one or more reflective coatings disposed on an interior surface of the housing 408. The secondary reflector 412 may be configured to reflect light so that a desired illumination pattern, such as low beam, flood beam, etc., may be emitted from the device 400. The secondary reflector 412 may also be configured to redirect backscattered primary and / or secondary light in a desired manner. The secondary reflector 412 may, for example, include a high-reflectivity surface for backscattered primary and / or secondary light.

[0069] The converter 401 may be located away from the light source 404 (as in Fig. 4A and Fig. 4B) or it may be disposed on the light-emitting surface 422 of the light source 404. In either case, the converter 401 may be formed separately from the light source 404 and coupled to the light source 404 in a known manner so that light emitted by the light source 404 can interact with the converter 401.

[0070] When the converter 401 is positioned at a distance from the light source 404, it may be supported within the housing 408 by any means, including support from a portion of a housing 408. Positioning the converter 401 at a distance from the light source 404 may allow the converter 401 to be formed with a shape different from the surface of the light source 404. For example, the converter 401 may be in the form of a plate, a dome, or a bowl. In any case, the surfaces of the converter 401 may be planar, concave, convex, elliptical, irregular, another shape, or a combination thereof.

[0071] For the sake of simplicity, the device 400 was Fig. 4A and Fig. 4B as comprising relatively few parts. However, it should be understood that the lighting devices of the present disclosure may include other components and electronics commonly found in solid-state lighting devices such as LED lamps. As an example, device 400 is shown as including a diffuser 414, which may serve to scatter the secondary light emitted by converter 401, as well as unconverted primary light.

[0072] Fig.5 illustrates a non-limiting example of a remote phosphor system 500 according to the present disclosure. As shown, the system 500 includes a wavelength conversion plate 507 having a converter 501 disposed within a recess in a reflector 502. The wavelength conversion plate 507 (shown in cross-section) is coupled to a heat sink 503. As can be understood, the heat sink 503 functions to remove heat generated by the wavelength conversion plate as it converts primary light to secondary light.

[0073] The system 500 further includes a light source 504. The light source 504 may have a substantially collimated excitation light output 505. Thus, the light source 504 may be, for example, a collimated lamp, an LED, a laser, or the like (e.g., a laser diode) that emits excitation light 505 at a desired power. The excitation light 505 may, for example, be laser light of any wavelength suitable to excite the converter 501 at average power levels of approximately 1-100 W or more, as required. The excitation light 505 emitted by the light source 504 may be incident on a dichroic beamsplitter 512, where it is reflected by focusing optics / focusing lens 508 to impinge on the converter 501. The converter 501 may absorb excitation light and emit secondary light 506.

[0074] As described above, the converter 501 typically emits secondary light in all directions, including to its sides and rearward. The reflector 502 may confine and reflect such secondary light such that it is redirected in a direction generally toward the focusing optics / focusing lens 508. In any event, the bulk of the secondary light emitted by the converter 501 is confined by a collection / focusing optic 509. As can thus be understood, the collection / focusing optic 509 may provide strong confinement for the secondary light. Consequently, the collection / focusing 509 may limit or otherwise prevent the loss of secondary light 506.

[0075] The secondary light 506 may be collimated as it passes through the focusing optics / focusing lens 508. All or a portion of the secondary light 506 may then pass through the dichroic beamsplitter 512, which is preferably transparent to (or transmits) 100% of the secondary light 506. The secondary light may then be further modified by the focusing lens / focusing concentrator 510. At this point, the secondary light 506 may enter an aperture of a device, e.g., a spectrometer, secondary reflector optics, a fiber optic coupler, an optical modulator, a data projector machine, or the like.

[0076] The wavelength conversion plates of the present disclosure can provide numerous advantages. For example, because the wavelength conversion plates described herein can be formed entirely of a ceramic material, they can exhibit high-temperature resistance. Consequently, they may be capable of functioning at higher operating temperatures than conventional wavelength conversion plates containing an organic material such as silicone, i.e., above about 150°C.

[0077] Furthermore, the wavelength conversion plates of the present disclosure may open up new avenues for thermal management, particularly in cases where the reflective material is composed entirely of inorganic materials, such as the ceramics noted above. In particular, the reflector material itself may provide a convection path for heat generated during the conversion process, which may enable the use of the wavelength conversion plates described herein in high-temperature and / or high-brightness applications.

[0078] Finally, the optical properties of the conversion material and the reflection material can be controlled by adjusting processing parameters such as particle size and particle size distribution during the formation of the wavelength conversion plates described herein. Consequently, wavelength conversion plates tailored to a specific application can be easily fabricated using the processes described herein.

[0079] Another aspect of the present disclosure relates to a wavelength conversion plate. The wavelength conversion plate may include a converter and a reflector coupled thereto. The converter may include a first ceramic material capable of converting incident primary light into secondary light. The reflector may include a second ceramic material capable of reflecting secondary light emitted by the converter. The wavelength conversion plate may also include an interface between the converter and the reflector. In some embodiments, the second ceramic material abuts the first ceramic material over at least about 50% of the interface, such as about 75% of the interface, or even about 100% of the interface. For clarity, the term "abut" is used herein to refer to contact between two adjacent surfaces.

[0080] Another aspect of the present disclosure relates to co-sintered ceramic wavelength conversion plates. Such plates may comprise a converter and a reflector. The converter may comprise at least a first ceramic material, and the reflector may comprise at least a second ceramic material. The reflector may also comprise at least one through-hole or at least one recess. The converter and the reflector may be co-sintered such that the reflector engages and retains the converter within the at least one through-hole or the at least one recess.

[0081] Another aspect of the present disclosure relates to a device. The device comprises a light source capable of emitting primary light and a wavelength conversion plate according to the present disclosure. In some embodiments, the device comprises a wavelength conversion plate comprising a converter and a reflector coupled thereto. The converter may comprise a first ceramic material capable of converting incident primary light into secondary light. The reflector may comprise a second ceramic material capable of reflecting secondary light emitted by the converter. The wavelength conversion plate may also comprise an interface between the converter and the reflector. In some embodiments, the second ceramic material is adjacent to the first ceramic material over at least about 50% of the interface, such asabout 75% of the interface or even about 100% of the interface.

Claims

[1] Wavelength conversion plate comprising: a plurality of converters (110), each converter comprising a ceramic material capable of converting incident primary light into secondary light, and each converter comprising a different material or having a different activator concentration, and the converters having a shape of nested concentric cylinders; a reflector (111) coupled to at least one of the plurality of converters, the reflector comprising a ceramic material capable of reflecting secondary light emitted by the converters, and the reflector material being different from the converter materials; and an interface (112) between at least one of the plurality of converters and the reflector, wherein the reflector surrounds an outer edge of the at least one converter, and wherein the reflector material is in contact with over at least about 50% of the interface. [2] The wavelength conversion plate of claim 1, wherein the reflector material is in contact with at least about 75% of the interface. [3] The wavelength conversion plate of claim 1, wherein the reflector material is in contact with over about 100% of the interface. [4] The wavelength conversion plate according to claim 1, wherein the ceramic material of the converters comprises at least one of an oxide phosphor, an oxynitride phosphor, a nitride phosphor, or a combination thereof. [5] The wavelength conversion plate according to claim 1, wherein the ceramic material of the converters is selected from a cerium-activated yttrium aluminum garnet (YAG:Ce), a cerium-activated yttrium gadolinium aluminum garnet (YGdAG:Ce), a cerium-activated lutetium aluminum garnet (LuAG:Ce), a cerium-activated lutetium gallium aluminum garnet (LuGAG:Ce), a europium-activated alkaline earth (AE) silicon oxynitride (AE-SiON:Eu), and a europium-activated metal SiAlON (M-SiAlON:Eu), where M is selected from a group consisting of alkali ions, rare earth ions, alkaline earth ions, Y, Sc, and combinations thereof. [6] The wavelength conversion plate according to claim 1, wherein the ceramic material of the reflector is selected from alumina (Al2O3), yttrium aluminum garnet (YAG), titanium dioxide (TiO2), barium aluminate (BaAl2O4), yttrium oxide (Y2O3), zirconium oxide (ZrO2), aluminum nitride (AlN), and combinations thereof. [7] The wavelength conversion plate of claim 1, wherein the reflector reflects more than or equal to about 80% of the secondary light. [8] A wavelength conversion plate according to claim 1, wherein the reflector comprises at least one through-hole (113) or at least one recess, and the converter is arranged within the at least one through-hole or the at least one recess. [9] The wavelength conversion plate according to claim 8, wherein the reflector comprises at least one through-hole. [10] A wavelength conversion plate according to claim 8, wherein the reflector comprises at least one recess. [11] The wavelength conversion plate of claim 8, wherein the reflector engages the converter to retain the converter within the at least one through-hole or the at least one recess. [12] A wavelength conversion plate according to claim 11, wherein at the interface a converter material is arranged in spaces within the reflector material. [13] A wavelength conversion plate according to claim 11, wherein at the interface the reflector material is arranged in spaces within a converter material. [14] The wavelength conversion plate of claim 11, wherein the reflector mechanically compresses the converter. [15] The wavelength conversion plate of claim 1, wherein the reflector has a thermal conductivity greater than or equal to about 80% of the thermal conductivity of the bulk form of the ceramic material of the reflector. [16] The wavelength conversion plate of claim 1, wherein the reflector has a thermal conductivity in the range of about 8 to about 35 W / mK. [17] A wavelength conversion plate according to claim 1, wherein the reflector consists of an upper reflector part and a lower reflector part. [18] A wavelength conversion plate according to claim 17, wherein the upper reflector part and the lower reflector part are made of different ceramic materials. [19] A wavelength conversion plate according to claim 17, wherein the upper reflector part has a through-hole and the lower reflector part is laminated to the upper reflector part to form a recess partially defined by the through-hole. [20] A wavelength conversion plate according to claim 1, wherein each converter has an activator concentration different from any other converter. [21] A wavelength conversion plate according to claim 20, wherein the converters are arranged in an order of decreasing activator concentration progressively from an innermost converter to an outermost converter. [22] A wavelength conversion plate according to claim 1, wherein the converter and the reflector are sintered together to bond the converter to the reflector. [23] A wavelength conversion plate according to claim 1, wherein an adhesive layer is used to fix the converter to the reflector. [24] A wavelength conversion plate according to claim 1, wherein the converter is fixed to the reflector by a compression force exerted by the reflector. [25] Device comprising: a light source capable of emitting primary light; and a wavelength conversion plate comprising: a plurality of converters, each converter comprising a ceramic material capable of converting incident primary light into secondary light, and each converter comprising a different ceramic material or having a different activator concentration, and the converters having the shape of nested concentric cylinders; a reflector coupled to at least one of the plurality of converters, wherein the reflector comprises a ceramic material capable of reflecting secondary light emitted by the converter, and wherein the reflector material is different from the converter materials; and an interface between the converter and the reflector, wherein the reflector surrounds an outer edge of the at least one converter, and wherein the reflector material is in contact with over at least about 50% of the interface. [26] The device of claim 25, wherein the converter materials comprise at least one oxide phosphor, oxynitride phosphor, nitride phosphor, or a combination thereof. [27] The device of claim 25, wherein the reflector material is selected from aluminum oxide (Al2O3), yttrium aluminum garnet (YAG), titanium dioxide (TiO2), barium aluminate (BaAl2O4), yttrium oxide (Y2O3), and combinations thereof. [28] The device of claim 25, wherein the reflector reflects more than or equal to about 80% of the secondary light. [29] The device according to claim 25, wherein the reflector comprises at least one through-hole or at least one recess and the converters are arranged within the at least one through-hole or the at least one recess. [30] The device of claim 29, wherein the reflector mechanically engages the converter to retain the converter within the at least one through-hole or the at least one recess. [31] The device of claim 25, wherein the reflector has a thermal conductivity in the range of about 8 to about 35 W / mK. [32] The device according to claim 25, wherein the light source comprises at least one light-emitting diode (LED) or laser diode.

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