Stable phosphor-converted LEDs and systems using same

Abstract

According to some embodiments, a method for manufacturing a semiconductor device includes: an enclosure defining an internal cavity, the cavity having a depth dimension; at least one LED chip; and a layer covering the at least one LED chip and disposed within the cavity, the layer including a blend of an encapsulant material and a phosphor composition, the phosphor composition comprising a yellow-green phosphor and a Mn 4+ and a doped complex fluoride phosphor, wherein Formula I is x [MF y ]:Mn 4+ (I), wherein A is Li, Na, K, Rb, Cs, NR4, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, a lower alkyl group, or a combination thereof; and x is [MF y ] is the absolute value of the charge of the ion, and y is 5, 6, or 7, and 4+ The doped complex fluoride phosphor has a d50 particle size of about 1 micrometer to about 10 micrometers, and the LED lighting device, when operated, emits visible light having a correlated color temperature (CCT) of about 2500 K to about 3700 K. Numerous other embodiments are also provided.

Description

[Technical field]

[0001] The present invention relates to stable phosphor-converted LEDs and systems using same. [Background technology]

[0002] The LED packaging industry values ​​narrow red emission from phosphor-converted LED packages. Obtaining improved red light down-conversion from blue light at a given luminous flux level from an LED source while improving damage resistance to high luminous flux is a challenge. Improved phosphor performance (e.g., higher conversion efficiency) and higher phosphor reliability (e.g., less material damage at higher LED luminous flux levels) are always sought when used in LED packages.

[0003] It would be desirable to provide a system and method for an improved phosphor-converted LED package. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Korean Patent Application Publication No. 10-2016-0085315 Summary of the Invention

[0005] According to some embodiments, an LED lighting device is provided, the LED lighting device comprising: an enclosure defining an internal cavity, the cavity having a depth dimension; at least one LED chip; and a layer including a blend of an encapsulant material and a phosphor composition, the layer covering the at least one LED chip and disposed within the cavity, the phosphor composition comprising a yellow-green phosphor and a Mn 4+ and a doped complex fluoride phosphor, wherein formula I is x [MF y ]:Mn 4+(I), wherein A is Li, Na, K, Rb, Cs, NR4, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, a lower alkyl group, or a combination thereof; and x is [MF y ] is the absolute value of the charge of the ion, y is 5, 6, or 7, and Mn 4+ The doped complex fluoride phosphor has a d50 particle size of about 1 micrometer to about 10 micrometers, and the LED lighting device emits visible light having a correlated color temperature (CCT) of about 2500K to about 3700K when operated.

[0006] According to some embodiments, a yellow-green phosphor and a Mn 4+ and a doped complex fluoride phosphor, wherein formula I is a phosphor precursor for a phosphor composition comprising: x [MF y ]:Mn 4+ (I), wherein A is Li, Na, K, Rb, Cs, NR4, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, a lower alkyl group, or a combination thereof; and x is [MF y is the absolute value of the charge of the ] ion, where y is 5, 6, or 7; producing a phosphor precursor for a phosphor composition of Formula I having a d50 particle size of about 1 micrometer to about 10 micrometers; producing a phosphor composition of Formula I from the produced phosphor precursor having a d50 particle size of about 1 micrometer to about 10 micrometers; constructing an LED lighting device with the produced phosphor composition; and emitting visible light having a CCT of about 2500K to about 3700K when the constructed LED lighting device is operated.

[0007] The present disclosure generally relates to red light emission from phosphor-converted LEDs. More specifically, the present disclosure relates to manganese-activated luminescent materials that are excited by blue or violet light (such as blue light emitted by an LED chip) and emit light in the red region of the visible spectrum, and LED packages that include such materials. Some technical effects of some embodiments disclosed herein include the same given Mn 4+ Improved lighting devices showing improved performance and reliability of Mn-activated red phosphors compared to conventional systems with different doping levels.

[0008] This and other advantages and features which will become apparent hereinafter, together with a more complete understanding of the nature of the present invention may be obtained by reference to the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1A] 1 is a scanning electron microscope (SEM) image of conventional large particle size PFS. [Figure 1B] 1 is an SEM image of a small particle size PFS according to some embodiments. [Diagram 2] FIG. 1 compares a conventional large particle size PFS with a small particle size PFS according to some embodiments. [Diagram 3] 1 is a process according to some embodiments. [Figure 4] 1 is a first non-exhaustive example of a lighting device according to some embodiments. [Diagram 5] 1 is a second non-exhaustive example of a lighting device according to some embodiments. [Figure 6] 1 is a third non-exhaustive example of a lighting device according to some embodiments. [Figure 7] 1 is a fourth non-exhaustive example of a lighting device according to some embodiments. [Figure 8] 1 is a fourth non-exhaustive example of a lighting device according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. However, it will be understood by those skilled in the art that the embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to obscure the embodiments.

[0011] One or more specific embodiments of the present invention are described below. In order to provide a concise description of these embodiments, not all features of an actual implementation may be described herein. As with any engineering or design project, it should be understood that in the development of such an actual implementation, numerous implementation-specific decisions may be made to achieve the developer's particular objectives, such as compliance with system-related and business-related constraints that may vary from implementation to implementation. It should further be understood that such a development effort may be complex and time-consuming, but would nevertheless be considered to be no more than a routine undertaking of design, fabrication, and manufacture for those of ordinary skill in the art having the benefit of this disclosure.

[0012] The approximation language used herein throughout the specification and claims is applicable to modify any quantitative expression that can be reasonably varied without causing a change in the basic function involved. Thus, a value modified by one or more terms such as "about" is not limited to the exact value specified. In some cases, the approximation language may correspond to the precision of the instrument that measures the value. For example, the term "about" used in the context of a wavelength value may refer to a wavelength value up to ±20 nm of the specified wavelength value, and is applicable to all occurrences of the term "about" used herein with respect to wavelength values ​​throughout the specification.

[0013] As used herein, the term "phosphor" or "phosphor material" or "phosphor composition" can be used to refer to both a single phosphor composition and a blend of two or more phosphor compositions. As used herein, the term "lamp" or "illumination device" or "illumination system" refers to any source of visible and / or ultraviolet light that can be produced by at least one light-emitting element (e.g., a phosphor material) that produces light emission when excited by a light-emitting diode.

[0014] As mentioned above, the present disclosure relates to manganese-activated luminescent materials that are excited by blue or violet light (such as blue light emitted by an LED chip) and emit light in the red region of the visible spectrum, and LED packages containing such materials. Such luminescent materials are referred to in the present disclosure as Mn-activated red phosphors of formula I, Mn 4+ Activator, or Mn 4+ Also referred to as doped complex fluoride phosphors, where Formula I is as follows: A x [MF y ]:Mn 4+ (I) wherein A is Li, Na, K, Rb, Cs, NR4, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, a lower alkyl group, or a combination thereof; and x is [MF y y is the absolute value of the charge of the ion, and y is 5, 6, or 7. A "lower" alkyl group is typically a hydrocarbyl group having from 1 to about 4 carbon atoms.

[0015] One non-exhaustive example of Mn-activated red phosphors is PFS (K2SiF6:Mn 4+ ) phosphor. This material is available to LED manufacturers for incorporation into LED packages.

[0016] The present disclosure relates to a system that uses Mn-activated red phosphor in an LED package, 4+ A system is described that exhibits improved performance and reliability of red phosphor compared to conventional systems with the same given doping level of activator. Some embodiments can utilize red phosphor particles that are significantly smaller (about 5 micrometers) compared to typical Mn-activated red phosphor particle sizes (about 30 micrometers). By incorporating smaller particle size Mn-activated red phosphor into the resin that encapsulates the LED package, the resulting LED package can exhibit improved red phosphor conversion efficiency and reduced susceptibility to damage from high luminous flux.

[0017] As used herein, a characteristic parameter of an LED package is often referred to as "red phosphor conversion efficiency" and sometimes also as "red-blue output ratio". Either name can refer to the ratio of the integrated power (e.g., units of measurement are radiant watts) under the emission curve in the red region of a resin-encapsulated red phosphor under blue LED excitation to the power under blue light excitation at a constant content of Mn activator in the host matrix. As a non-limiting example, the blue output can be measured by integrating the radiant output from the package in the range of 400 nm to 477 nm, while the red output can be measured by integrating the radiant output from the package in the range of 550 nm to 700 nm (note, however, that the exact wavelength range of integration is selected to ensure that all measured red and blue outputs are taken into account in the calculation. These specific ranges depend on the source and emission spectrum, as will be well understood by those skilled in the art). K2SiF6:Mn 4+ In the case of Mn-activated red phosphors that are Mn-activated red phosphors (i.e., PFS), the LED packages of one or more embodiments that use small particle size PFS encapsulated in resin have a Mn to K2SiF6 ratio. 4+It can show higher red phosphor conversion efficiency compared to the same LED package using PFS with the same molar content but larger particle size. Of course, other host matrices are possible, as suggested by the range of formula I above (e.g., K2TiF6:Mn 4+ red phosphor K2TiF6, etc.

[0018] When a certain small particle size of Mn-activated red phosphor is included in the resin encapsulating the LED package, a more robust red phosphor-containing LED package can be obtained that can operate more efficiently and at higher luminous flux levels compared to conventional LED packages that include larger particle size Mn-activated red phosphor. The performance improvement can be most significant when the particle size of the phosphor is reduced from about 30 μm to about 5 μm, although other values ​​are possible. As discussed above, LED packages made according to the present disclosure can convert significantly more red light when excited by a blue LED. Without being limited by theory, it is believed that (due to the small particle size of the Mn-activated red phosphor) the red phosphor can remain better dispersed in the resin encapsulation material (e.g., industry standard silicone epoxy) that is commonly used to manufacture white LEDs. Such improved dispersion can allow for less damage to the red phosphor at higher luminous flux. It is noted that similar results can be obtained with other types of encapsulation materials, such as silicone resins, epoxy resins, acrylate resins, or combinations thereof.

[0019] The system of the present disclosure can be used to construct warm white LED packages, cool white LED packages, or any other suitable LED packages having robust Mn-activated red phosphors for indoor or outdoor lighting or display applications.

[0020] Red phosphor "Red phosphor of the present disclosure" means a Mn-doped red phosphor of Formula I. A non-exhaustive example of such a red phosphor is PFS, i.e., K2SiF6:Mn.

[0021] Small particle size red phosphor The small particle size red phosphors of the present disclosure (having a particle size of 10 microns or less) may be made by any suitable method, for example, by a wet milling system as described in Beers' US Patent Application Publication No. 20160289553, which illustrates the achievement of red phosphors of formula I in the size range of 1 micron to 30 microns and is incorporated herein by reference in its entirety for all purposes. As described therein, the phosphor precursor is milled into particles, and the milled particles are then treated to improve the performance and stability of the resulting manganese-doped red phosphor, and the milled and treated phosphor precursor particles are further treated to provide the final manganese-doped red phosphor. The phosphor precursor is milled (or ground) to reduce the particle size for the desired properties. The milling or grinding of the particles of the phosphor precursor of formula I may be performed for a selected period of time at a rotary milling speed that depends in part on the size of the particles before milling and the desired size of the particles obtained after milling. Other methods for achieving the small sizes described by the present disclosure are also possible.

[0022] In some embodiments, the particles can be treated before or after milling to enhance the performance and stability of the resulting small particle size Mn-doped red phosphor. As part of the above-mentioned performance and stability enhancement treatment, in one embodiment, the milled particles can be contacted with a gaseous fluorine-containing oxidizing agent at high temperature. Other methods for improving performance and stability may also be possible. In some embodiments (but not in other embodiments), the small particle size red phosphor of the present disclosure can be subjected to a color stabilization treatment, such as by annealing in a fluorine-containing oxidizing atmosphere at high temperature, as disclosed in prior commonly owned US Patent Application Publication No. 20150361335 and US Patent No. 9698314, both of which are incorporated herein by reference in their entirety for all purposes.

[0023] Particle size measurement As used in this disclosure, the determination of particle size of Mn-doped red phosphor having a nominal diameter of about 10 microns or less is performed via image analysis. That is, laser light scattering techniques are not usually used to determine the particle size of Mn-doped red phosphor when the nominal diameter is about 10 microns or less. Instead, microscopic image analysis is usually performed using SEM (scanning electron microscopy). Those skilled in the art will understand how to use scanning electron microscopy to determine the average particle size of primary particles, i.e., non-agglomerated particles. For example, a scanning electron microscope image of a powder sample can be obtained at a magnification of 1500 times. This image can be post-processed, where image processing is applied to enhance the edges of the particles and convert the image into a binary image. Particle statistics can then be collected and a volume-based particle size distribution report can be extracted to arrive at a particle size index called d50, where 50% of the particles in the sample are larger than the d50 value and 50% of the particles in the sample are smaller than the d50 value. This is essentially the method defined in this disclosure for finding the particle size of PFS phosphors with a nominal diameter of 10 microns or less. In general, the distribution can be normalized to either the total number of particles or the total volume of particles. However, to be consistent with industry standard reporting (e.g., diffraction-based measurement systems), it is reported here on a volume basis. In summary, an image is acquired and, at a given magnification, the average size of the primary particles is determined.

[0024] High light flux stability As mentioned above, when used as part of a phosphor composition dispersed in a polymer matrix, and when containing an appropriately small particle size (i.e., 10 microns or less), the phosphor composition of the present disclosure may suffer less damage due to high light flux. This is typically measured by laser damage upon exposure to a blue laser for a specified time period. Laser damage is a proxy for the accelerated aging or degradation that the phosphor composition would suffer when exposed to blue LED light for extended periods of time as part of an LED package during use. As an example, a conventional PFS phosphor of a conventional size may typically suffer a laser damage value of 2% after 24 hours of exposure to a test blue laser light. This refers to a 2% decrease in the luminous output of the phosphor after treatment with a laser for a specified time period. However, a Mn-activated red phosphor with a specified small particle size (i.e., 10 microns or less) of the present disclosure (when dispersed in a polymer encapsulation matrix and used in accordance with the claimed invention) may exhibit only half the laser damage of a conventional PFS phosphor.

[0025] The laser damage accelerated aging test can typically be performed according to the following general procedure: A small particle size phosphor composition is dispersed in an encapsulated polymer resin and formed into a tape. A blue semiconductor laser is then effectively placed at the bottom of the tape similar to where the LED chip would be in an LED package. A laser diode emitting at 445 nm is coupled into an optical fiber with a collimator on the other end. The power output can be about 280 mW and the beam diameter at the sample can be 600 microns. This results in a beam size of about 100 W / cm2 at the sample surface. 2is equivalent to a luminous flux of 10 ...

[0026] Without being limited by theory, the reason for the less laser damage and therefore less degradation over time in this small particle size PFS phosphor is due to a more favorable configuration distributed in the encapsulating resin compared to conventional PFS blends suspended in the encapsulating resin.

[0027] Phosphor Composition An embodiment of the present invention relates to an LED package comprising a blue semiconductor light source radiatively coupled to a resin encapsulant containing a phosphor blend or composition. Radiatively coupled means that the elements are associated with each other so that radiation from one element is transmitted to the other element. The phosphor composition includes the small particle size Mn-doped red phosphors (e.g., PFS) described above, as well as yellow-green phosphors such as YAG (yttrium aluminum garnet) or LAG (lanthanum aluminum garnet), or any effective yellow-green phosphor that can produce the BSY effect (blue-shifted yellow), in order to produce light that appears white in certain embodiments. In some preferred embodiments, the d50 value of the particle size of the Mn-doped red phosphor is about or substantially 5 micrometers in diameter. The phosphor composition in the LED package of the embodiment of the present disclosure may further include one or more of additional red phosphors or quantum dots (narrow or wide), additional yellow phosphors or quantum dots, additional green phosphors (e.g., beta-sialon) or quantum dots, blue phosphors or quantum dots, or orange phosphors or quantum dots. It may further include one or more luminescent quantum dots of these luminescent colors (quantum dots are luminescent inorganic semiconductor particles of a specific size, typically with nanometer-scale dimensions). In some embodiments, the yellow-green phosphor may be partially or entirely replaced with a beta-sialon phosphor, such as a europium (II)-doped β-SiAlON phosphor. In some embodiments, the additional red phosphor may include a red europium-doped silicon nitride phosphor (e.g., SCASN or CASN).

[0028] Particle size range: selection and effects Exemplary embodiments of particle sizes for small particle size Mn-doped red phosphors of the present disclosure include the use of 5 micron sized particles (d50) and 10 micron sized particles. Increasing particle size monotonically decreases the red to blue luminous output ratio. For Mn-doped red phosphors with a size of about 20 microns, the red to blue luminous output ratio is not significantly different from that observed for conventional 30 micron sized particles. According to embodiments of the present disclosure, the d50 particle size may be in the range of about 1 micron to about 10 microns. More specifically, the d50 particle size may be in the range of about 5 microns to about 10 microns. Below about 1 micron, the difficulties in handling such small particle size Mn-doped phosphors may become too great. Above about 20 microns, the improvement in the red to blue luminous output ratio over conventional 30 micron particle size Mn-doped phosphors becomes less or non-existent.

[0029] It should be noted that the red / blue ratio can also be estimated from the color point, more specifically, the chromaticity (ccx, ccy) value from the 1931 CIE chromaticity diagram. Furthermore, by comparing the ccx value of the light emitted by an LED package using a small particle size PFS with a similar LED package having a conventional larger particle size, one skilled in the art can estimate the improvement of the red / blue ratio.

[0030] By using the particular small particle size range of Mn-doped red phosphor disclosed in one or more embodiments, an LED package can be provided (e.g., constructed or achieved) that can emit light with a correlated color temperature (CCT) in the range of about 2500 Kelvin to about 3500 Kelvin (e.g., about 3000K). Because of the small particle size, an improved red output can be achieved even with a lower weight percentage of phosphor loading of the Mn-doped red phosphor. As a result, a relatively low weight percentage of the Mn-doped red phosphor can be used to achieve the desired CCT even at typical depths of the LED package cavity. It is noted that while it may be possible to achieve a CCT of about 2500K to 3500K without using small particle size Mn-doped red phosphor, it would require excessively large phosphor loadings or extremely high levels of Mn dopant. The inventors of the present invention have determined that an excessively large weight percentage of manganese-doped red phosphor in the encapsulated blend can lead to reliability issues. Therefore, it may be advantageous to keep the phosphor loading level relatively low. However, even with the constraint of low phosphor loading, high red output can help achieve color temperature correlated color temperatures in the range of 2500 Kelvin to 3500 Kelvin. The small particle size manganese doped red phosphor of one or more embodiments is a solution to this tradeoff, since it can emit the required amount of red from its emission even when present at acceptable phosphor loading levels.

[0031] As a non-exhaustive example, the phosphor loading level of one or more embodiments may be less than about 50 weight percent, i.e., less than about 50 grams of total phosphor for every 100 grams of combined mass of encapsulation resin and total phosphor. Other suitable amounts may be used. Due to the higher red output of the small particle size phosphor of one or more embodiments, LED packages may be reliably constructed at moderate color temperatures, such as 2500K to 3500K.

[0032] In some embodiments, the LED packages of the present disclosure can be configured as warm white LED packages (CCT of 2500K-3500K) in a mid-power configuration and achieve an L90 of greater than 36000 hours (i.e., 90% of the lumens are retained after 36000 hours). In other embodiments, the LED packages of the present disclosure can be configured as cool white LED packages (CCT of 3500K-5000K) in a mid-power configuration and achieve an L90 of greater than 36000 hours at greater than 100mA for a mid-power LED package of about 1W.

[0033] 1A and 1B, SEM images of representative samples of large grain PFS 102 (FIG. 1A) and small grain PFS 104 (FIG. 1B), respectively, are presented. In FIG. 1A, the large grain size (d50 grain size of about 28 micrometers) is typical of many conventional PFS phosphors. In this example, the PFS of FIG. 1A had a Mn doping level of 1.5 atom%, an initial red / blue ratio (at 100 W / cm2) of 3.6, and a laser damage level of 2%. In contrast, FIG. 1B is typical of the small grain PFS of the present disclosure, which has a grain size of 5 micrometers (d50) and a Mn dopant level of 1.4%, yet when incorporated into silicone resin and encapsulated in an LED package, had an initial red / blue ratio of about 6.0 and laser damage of only 1.0%. EXAMPLES

[0034] FIG. 2 shows experimental results 200 for the use of the disclosed 5 micron grain PFS phosphor against a conventional 30 micron grain PFS phosphor with various manganese dopant levels in the PFS. The solid dots 202 in FIG. 2 refer to 30 micron PFS phosphors that are encapsulated in silicone resin and form part of an LED package. The various solid dots 202 are located at various content levels of tetravalent manganese in the doped PFS phosphor. For example, the bottom left dot 202 is for a 30 micron PFS phosphor with a manganese doping level of about 1.46% (relative to the central Si atom in the host). The use of such phosphors shows a red / blue output ratio of less than 3.5. Increasing the manganese level to about 1.77% manganese does not increase the red / blue ratio beyond about 4.5. However, the use of PFS phosphors with particle size (average d50) of 5 microns dispersed in a silicone encapsulant can enable achievement of red / blue output ratios of greater than 5.5, as shown by the open dot 204 in the upper left corner of Table I. Note that references to manganese content determined by X-ray fluorescence spectroscopy refer to the determination of the atomic percentage of manganese dopant in the Mn-doped red phosphors. EXAMPLES

[0035] Table I below shows experimental results for PFS phosphors of various nominal particle sizes. [Table 1]

[0036] The particle size, measured as the d50 particle size, is given in the first column of Table I. The LD (laser damage parameter) is given in the subsequent columns of the table, and the red / blue power ratio is given in the right-most column of the table. With a nominal particle size of 30 microns (a conventional particle size and not part of this invention) and an atomic percentage of manganese of 1.47% measured by X-ray fluorescence, the laser damage and red / blue ratio values ​​are not acceptable. In one implementation, the laser damage was 1.6% (after irradiation with a blue power of 100 watts per square centimeter). For this same sample, the red / blue power ratio was 3.48. In another implementation, the laser damage was 2.0% and the red / blue ratio was 3.56, measured by the same method. However, when a 5 micron PFS phosphor was used with a similar manganese content (i.e., 1.54%), the laser damage was only 1.0% and the red / blue ratio improved to 6.25.

[0037] It should be noted that the LED package is an LED lighting device of the present disclosure and can be adopted for general lighting applications such as lamps for general lighting, etc. However, the LED package of the present disclosure may also be used for signage, backlighting for displays, outdoor lighting, indoor equipment, signals, televisions, portable devices, decorative lighting, or any other applications in which the LED package can be appropriately used.

[0038] 3-7, examples of lighting devices 40 (FIGS. 4, 5, 6, 7) and operation according to some embodiments are shown. In particular, FIG. 3 shows a flow diagram of a process 300 according to some embodiments. Process 300, and any other processes described herein, may be performed using any suitable combination of hardware (e.g., circuitry), software, or manual means. Examples of these processes are described below with respect to system embodiments, but the embodiments are not limited thereto. The flow diagrams described herein do not imply a fixed order of steps, and embodiments of the invention may be performed in any order that is feasible.

[0039] With particular reference to FIG. 3, a process for making a small particle size phosphor composition for use in a lighting device 40 is provided. First, in S310, a phosphor precursor is received. Then, in S312, the phosphor precursor is processed. In one or more embodiments, the phosphor precursor can be processed to obtain a desired particle size. As mentioned above, as a non-exhaustive example, the processing can include grinding the phosphor precursor. In some embodiments, the particle size can be measured, for example, by scanning electron microscopy (SEM) to determine whether the particle size after grinding is the desired size (i.e., small particle size). Furthermore, in one or more embodiments, the phosphor precursor can be processed before or after grinding to enhance the performance and stability of the resulting small particle size red phosphor. As a non-exhaustive example, the phosphor precursor can be contacted with a gaseous fluorine-containing oxidizing agent at high temperature and can be subjected to a color stabilization treatment, such as by annealing in a fluorine-containing oxidizing atmosphere at high temperature. Then, in S314, a phosphor is produced using the phosphor precursor via any suitable phosphor production process. The resulting small particle size red phosphor is then used to construct a lighting device in S316. In one or more embodiments, the lighting device, when activated, emits visible light having a CCT of about 2500 K to about 3700 K. In some embodiments, the lighting device, when activated, emits visible light having a CCT of about 2500 K to about 3500 K.

[0040] With reference to FIG. 4, a lighting device 40 is provided that includes a phosphor material radiatively coupled to a light source according to some embodiments of the present disclosure. As used herein, the terms "lighting device," "illumination device," "light emitting assembly," and "lamp" may be used interchangeably. The lighting device 40 includes an enclosure (e.g., an envelope / shell / encapsulant 18) within which a cavity 10 is defined, the cavity 10 having a depth dimension of about 200 microns to about 800 microns. The lighting device 40 includes a semiconductor radiation source, shown as a light emitting diode (LED) chip 42, and leads 44 electrically attached to the LED chip 42. The leads 44 may be thin wires supported by a thicker lead frame 46, or the leads may be self-supporting electrodes and the lead frame may be omitted. The leads 44 provide current to the LED chip 42, causing it to emit radiation. Although the examples of FIGS. 4-6 show one LED chip, any other suitable number of LED chips may be included in the lighting device 40.

[0041] The lighting device 40 can include any semiconductor blue or ultraviolet light source capable of producing white light when the emitted radiation is directed towards the small particle size red phosphor of the present disclosure. In one embodiment, the semiconductor light source is a blue light emitting LED. The LED chip 42 can comprise a semiconductor diode based on any suitable III-V, II-VI, or IV-IV semiconductor layers and having an emission wavelength of about 250 nm to 550 nm. The LED chip 42 can be, for example, a semiconductor diode of the formula In having an emission wavelength greater than about 250 nm and less than about 550 nm. i Ga j Al kN, where 0≦i, 0≦j, 0≦k, and i+j+k=l. More specifically, the LED chip 42 may be a near UV or blue emitting LED having a peak emission wavelength of about 350 nm to about 500 nm. The radiation source is described herein as an LED for convenience. However, as used herein, the term is intended to encompass all semiconductor radiation sources, including, for example, semiconductor laser diodes. Furthermore, while the general discussion of the exemplary structures of the invention discussed herein is directed to inorganic LED-based light sources, it should be understood that, unless otherwise indicated, the LED chip can be replaced with another radiation source, and reference to semiconductor, semiconductor LED, or LED chip is merely representative of any suitable radiation source, including, but not limited to, organic light emitting diodes.

[0042] In the lighting device 40, a layer 22 including a blend of the encapsulant material 20 and the small particle size red phosphor of the present disclosure is overlaid on at least one LED chip 42 disposed within a cavity. Note that in some embodiments, such as FIG. 4, the overlaid layer 22 may directly contact the at least one LED chip 42, but in some embodiments, such as FIG. 5 and FIG. 6, the overlaid layer 122, 222 may not directly contact the at least one LED chip 42. The layer 22, 122, 222 may be disposed within the cavity 10. The layer 22 radiatively couples to the chip 42. The layer 22 may be deposited on the LED 42 by any suitable method known in the art. For example, an aqueous suspension of phosphor may be formed and applied to the LED surface as a phosphor layer. In one such method, a silicone slurry with randomly suspended phosphor particles is disposed around the LED. This method is merely exemplary of a possible arrangement of the layer 22 and the LED 42. Thus, layer 22 can be coated over or directly onto the light emitting surface of LED chip 42 by coating and drying a phosphor suspension onto LED chip 42. In the case of a silicone-based suspension, the suspension is cured at an appropriate temperature.

[0043] In one or more embodiments, the LED chip 42 may be at least partially covered by an envelope 18 or lens 19 (FIG. 8) that surrounds the LED chip 42 and an encapsulant 20. Both the envelope 18 and the encapsulant 20 must be transparent to allow the emitted light to pass through these elements. The envelope 18 may be, for example, glass or plastic. The LED chip 42 may be encapsulated by the encapsulant 20. The encapsulant 20 may be at least one of low temperature glass, thermoplastic, thermosetting polymer, and resins known in the art, such as silicone resin or epoxy resin. In an alternative embodiment, the lighting device 40 may include only the encapsulant 20 without the envelope 18 to form the cavity 10. It is noted that the same type of encapsulant may be used for both the blend layer 22, 122, 222 and the encapsulant 20 that forms the cavity 10.

[0044] Various configurations of lighting device 40 are known in the art. For example, in some embodiments, small particle size red phosphor 22 of the present disclosure (which in one embodiment is disposed on the surface of chip 42 in FIG. 4) may alternatively be interspersed within encapsulant 120 as shown as 122 in FIG. 5 instead of being disposed directly on LED chip 42. Corresponding numbers in FIGS. 4-6 (e.g., 22 in FIG. 4 and 122 in FIG. 5) refer to corresponding structures in each figure unless otherwise noted. Small particle size red phosphor 122 of the present disclosure (in the form of a powder) may be interspersed within a single region of encapsulant 120 or throughout the entire volume of the encapsulant. The radiation emitted by the LED chip (not shown in FIG. 4, but shown as 126 and 226 in FIG. 5 and FIG. 6, respectively) mixes with the light emitted by the small particle red phosphor 22 / 122 / 222 of the present disclosure to produce the desired light emission (shown by arrow 24 in FIG. 4, arrow 124 in FIG. 5, and arrow 224 in FIG. 6). When the small particle red phosphor material 122 is interspersed within the material of the encapsulant 120, the small particle red phosphor powder of the present disclosure can be added to a polymer or silicone precursor, and the mixture can then be cured to solidify the polymer or silicone material. Examples of polymer precursors include thermoplastic or thermosetting polymers or resins, such as epoxy resins. Other known methods of interspersing phosphors, such as transfer loading, can also be used.

[0045] In some other embodiments, the small particle red phosphor of the present disclosure may be coated on the surface of the envelope 218 as shown in FIG. 6. The small particle red phosphor 222 of the present disclosure is preferably coated on the inner surface of the envelope 218, but the small particle red phosphor of the present disclosure may be coated on the outer surface of the envelope 218 if desired. The small particle red phosphor of the present disclosure may be coated on the entire surface of the envelope or only on the upper part of the surface of the envelope. The radiation emitted by the LED chip 42 mixes with the light emitted by the small particle red phosphor of the present disclosure, and the mixed light appears as white light 224. Of course, the structures of FIGS. 4-6 can be combined, and the small particle red phosphor of the present disclosure may be placed in any two or all three locations, or in any other suitable location, such as separate from the shell or integrated into the LED. Additionally, different phosphor blends may be used in different parts of the structure.

[0046] Another structure (particularly for backlighting applications) is a surface mounted device ("SMD") type light emitting diode 700, for example as shown in FIG. 7. The SMD is "side-emitting" and has a light emitting window 702 in the protruding portion of the light guide 704. The SMD package can include an LED chip as described herein and a small particle size red phosphor of the present disclosure. Other backlighting devices include, but are not limited to, televisions, computers, and handheld devices such as smartphones and tablet computers.

[0047] In any of the above structures, the lighting device 40 may further include a plurality of particles (not shown) for scattering or diffusing the emitted light. These scattering particles are typically embedded in the encapsulation material 20 / 120 / 220. The scattering particles may include, for example, particles made of alumina (Al2O3) or titanium dioxide (TiO2). The scattering particles may effectively scatter the light emitted from the LED chip 42, preferably with negligible absorption.

[0048] While only certain features of the invention have been illustrated and described herein, numerous modifications and changes will occur to those skilled in the art, and it is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. [Explanation of symbols]

[0049] 10 Cavity 18 Enclosures, envelopes and encapsulating materials 19 Lenses 20 Encapsulating Materials 22 Blend layer, layer, red phosphor 24 Arrow 40 Lighting Equipment 42 LED chips 44 Lead 46 Lead Frame 120 Encapsulating Materials 122 Blend layer, layer, red phosphor 124 Arrow 200 Experimental Results 218 Envelope 220 Encapsulating Materials 222 Blend layer, layer, red phosphor 224 White light, arrow 300 processes 700 Surface Mount Device ("SMD") Light Emitting Diode 702 Illuminating window 704 Light guide member

Claims

1. 1. A method comprising: A yellow-green phosphor and Mn of formula I ４＋ and a doped complex fluoride phosphor, the phosphor precursor having formula I A ｘ [MF ｙ ]:Mn ４＋ (I) wherein A is Li, Na, K, Rb, Cs, NR4, or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, a lower alkyl group, or a combination thereof; and x is [MF ｙ ] ion, and y is 5, 6, or 7; providing a phosphor precursor for said phosphor composition having a d50 particle size of 1 micrometer to 10 micrometers; forming said phosphor composition from said formed phosphor precursor having a d50 particle size of 1 micrometer to 10 micrometers; constructing an LED lighting device (40) with the produced phosphor composition; emitting visible light having a CCT of 2500K to 3700K when the constructed LED lighting device (40) is operated; Including, forming a phosphor precursor for said phosphor composition having a d50 particle size of 1 micrometer to 10 micrometers, grinding said phosphor precursor to a d50 particle size of 1 micrometer to 10 micrometers; Including, The method comprises: obtaining a scanning electron microscope image of said ground phosphor precursor; processing the scanning electron microscope image to enhance grain edges; determining from the processed scanning electron microscope image that the ground phosphor precursor has a d50 particle size of 1 micrometer to 10 micrometers; The method further comprising:

2. The step of constructing the LED lighting device (40) comprises: Providing an enclosure (18) defining a cavity (10); Producing a layer (22) comprising a blend of an encapsulant material (20) and the produced phosphor composition; applying the produced layer (22) to at least one LED chip (42) of the LED lighting device (40); 2. The method of claim 1, further comprising: wherein the at least one LED chip (42) is disposed within the cavity (10).

3. The method of claim 2, wherein the CCT is between 2500K and 3500K.

4. The method of claim 2, wherein the depth dimension of the cavity (10) is between 200 microns and 800 microns.

5. The method of claim 2 , wherein the encapsulating material (20) is at least one of a low temperature glass, a thermoplastic, a thermoset polymer, and a resin.

6. The method of claim 5 , wherein the resin is one of a silicone resin or an epoxy resin.

7. The method of claim 2 , wherein the LED chip (42) and the layer (22) are partially covered by the enclosure (18).

8. The method of claim 2 , wherein the encapsulating material (20) forms the enclosure (18).

9. The method of claim 2 , wherein the LED chip (42) and encapsulant (20) are at least partially covered by a lens (19).

10. The method of claim 2 , wherein the layer (22) comprising a blend of the encapsulant material (20) and a phosphor composition is radiatively coupled to the LED chip (42).

11. The method of claim 2 , wherein the layer (22) radiatively couples to the at least one LED chip (42).

12. grinding for a selected period of time at a rotational grinding speed that depends in part on the size of the phosphor precursor before grinding and the desired size of the ground phosphor precursor. The method of claim 1 further comprising:

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