Material arrangement in cover structure of package for light-emitting diode

Abstract

Disclosed is a material arrangement in a cover structure for a solid-state lighting device including a light-emitting diode (LED), more particularly for tunable LEDs. Disclosed is a material arrangement in a cover structure for a solid-state lighting device including a light-emitting diode (LED), more particularly for tunable LEDs. The material arrangement includes light-filtering particles or ionic species integrated within the material of a cover structure (14) that covers an LED chip within an LED package (10, 20, 30,...). The light-filtering material (16) is configured to selectively filter one or more portions of light provided by the LED chip (12) and / or the luminescent material (18) within the LED package. Dispersing the light-filtering material within the cover structure provides protection and mechanical support for the light-filtering material. Additionally, the arrangement and concentration of the light-filtering material within the cover structure can be varied horizontally and / or vertically to tune the light-emitting pattern of the corresponding LED package. The material arrangement includes light-filtering species incorporated at the atomic level within the cover structure. A further material arrangement may include photochromic particles configured to proportionally scatter light based on the relative intensity of the light from the LED chip.

Description

[Technical Field]

[0001]

[0001] The present invention relates to solid-state lighting devices including light-emitting diodes (LEDs), and more particularly to material arrangements in cover structures for LEDs. [Background technology]

[0002]

[0002] Solid-state light-emitting devices, such as light-emitting diodes (LEDs), are increasingly being used in both consumer and commercial applications. Advances in LED technology have resulted in light sources that are highly efficient, mechanically robust, and long-life. Modern LEDs are therefore enabling a variety of new display applications and are increasingly being used for general lighting applications, frequently replacing incandescent and fluorescent light sources.

[0003]

[0003] An LED is a solid-state device that converts electrical energy into light and typically contains one or more active layers (or active regions) of semiconductor material disposed between oppositely doped n-type and p-type layers. When a bias is applied across the doped layers, holes and electrons are injected into the active layer(s), where they recombine to produce light, such as visible or ultraviolet light. An LED chip typically contains an active region that may be fabricated from, for example, silicon carbide, gallium nitride, gallium phosphide, aluminum nitride, gallium arsenide-based materials, and / or organic semiconductor materials. Photons generated by the active region travel in all directions. A lumiphoric material may be disposed that converts at least a portion of the light generated from the active region of the LED chip to a different wavelength.

[0004]

[0004] LED packages have been developed to provide mechanical support, electrical connections, and encapsulation for the LED emitter and light-emitting material. As LED technology continues to advance, LED packages that emit high-quality colored light are needed for a variety of applications. Despite recent advances in LED package technology, challenges remain for producing high-quality light with desirable light-emitting characteristics while also providing high luminous efficacy in LED packages. Summary of the Invention [Problem to be solved by the invention]

[0005]

[0005] The art continues to seek improved LEDs and solid state light emitting devices with desirable lighting characteristics that can overcome the challenges associated with conventional LED devices. [Means for solving the problem]

[0006]

[0006] The present disclosure relates to solid-state lighting devices including light-emitting diodes (LEDs), and more particularly to a material arrangement in a cover structure for an LED that tailors light emission. The material arrangement includes light-filtering particles or ionic species integrated within the material of the cover structure that covers an LED chip within an LED package. The light-filtering material can be configured to selectively filter one or more portions of light provided by the LED chip and / or by the light-emitting material within the LED package. Incorporating the light-filtering material within the cover structure provides protection and mechanical support for the light-filtering material. Additionally, the arrangement and concentration of the light-filtering material within the cover structure may be varied horizontally and / or vertically to tailor the light emission pattern of the corresponding LED package. The material arrangement includes light-filtering species atomically integrated within the cover structure. A further material arrangement includes photochromic particles configured to proportionally scatter light based on the relative intensity of the light from the LED chip.

[0007] In one aspect, an LED package includes a submount; at least one LED chip on the submount, the at least one LED chip configured to generate light in a first peak wavelength range; and a cover structure on the at least one LED chip, the cover structure including a plurality of light filtering materials integrated therein, the light filtering materials configured to reduce emission of specific wavelengths from the cover structure. In certain embodiments, the plurality of light filtering materials include a plurality of light filtering particles. In certain embodiments, the plurality of light filtering materials include a plurality of light filtering ionic species incorporated within a host material of the cover structure. In certain embodiments, the light filtering materials are configured to reduce the amount of light within at least a portion of the first peak wavelength range from the cover structure without wavelength conversion of the light in the first peak wavelength range within the cover structure. In certain embodiments, the cover structure includes glass, and the plurality of light filtering materials are incorporated within the glass.

[0008] In certain embodiments, the LED package may further include a luminescent material between the cover structure and the at least one LED chip, the luminescent material configured to convert a portion of light in a first peak wavelength range to light in a second peak wavelength range. In certain embodiments, the light filtering material is configured to reduce the amount of light within at least a portion of the first peak wavelength range that exits the cover structure more than the amount of light within the second peak wavelength range. In certain embodiments, the light filtering material is configured to reduce the amount of light within at least a portion of the second peak wavelength range that exits the cover structure. In certain embodiments, the light filtering material is configured to reduce emission of light with wavelengths less than 400 nanometers that exits the cover structure. In certain embodiments, the light filtering material is configured to reduce emission of light with wavelengths greater than 700 nanometers that exits the cover structure. In certain embodiments, the LED package may further include luminescent material particles dispersed within the cover structure along with the light filtering material.

[0009] In certain embodiments, the light filtering material is disposed in a higher concentration near the peripheral edge of the cover structure than near the central portion of the cover structure. In certain embodiments, the light filtering material is disposed in a higher concentration along the central portion of the cover structure than near the peripheral edge of the cover structure. In certain embodiments, the light filtering material is disposed within the cover structure so that its concentration varies perpendicular to the LED chip. In certain embodiments, the light filtering material comprises at least a first filter type and a second filter type, the second filter type being configured to selectively filter a different wavelength range than the first filter type.

[0010] In another aspect, an LED package includes a submount, at least one LED chip on the submount, and a plurality of photochromic particles disposed on the at least one LED chip, the plurality of photochromic particles configured to variably scatter light from the at least one LED chip based on the relative intensity of the light from the at least one LED chip. In certain embodiments, the plurality of photochromic particles are configured to reduce scattering of light from the at least one LED chip when the intensity of light from the at least one LED chip decreases. The LED package may further include a cover structure over the at least one LED chip, the plurality of photochromic particles being dispersed within the cover structure. The LED package may further include light filtering particles dispersed within the cover structure. The LED package may further include luminescent material particles dispersed within the cover structure. In certain embodiments, the plurality of photochromic particles are configured to reduce scattering of light from the luminescent material particles when the intensity of light from the at least one LED chip decreases. In certain embodiments, the plurality of photochromic particles comprises one or more of an organic compound, a silicate photochromic glass containing silver halide microcrystals, and activated crystals of an alkali metal halide compound.

[0011] In other aspects, any of the foregoing aspects may be combined individually or together, and / or with various separate aspects and features described herein to provide additional advantages. Any of the various features and elements disclosed herein may be combined with one or more of the other disclosed features and elements, unless indicated to the contrary herein.

[0012] Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in conjunction with the accompanying drawings.

[0013] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure. [Brief explanation of the drawings]

[0013] [Figure 1]

[0014] FIG. 1A is a cross-sectional view of a light emitting diode (LED) package including an LED chip with a cover structure including a light filtering material according to an embodiment disclosed herein.

[0015] FIG. 1B is an exploded view of the LED package of FIG. 1A overlaid with a plot of the light spectrum illustrating exemplary filtering characteristics. [Figure 2]

[0016] 2 is a cross-sectional view of an LED package similar to that of FIG. 1 illustrating additional package elements. [Figure 3]

[0017] 3 is a cross-sectional view of an LED package similar to that of FIG. 2 for an embodiment in which the luminescent material is provided as luminescent particles dispersed within the cover structure along with a light filtering material. [Figure 4]

[0018] 3 is a cross-sectional view of an LED package similar to that of FIG. 2 for an embodiment in which the LED package does not include luminescent material. [Figure 5]

[0019] 3 is a cross-sectional view of an LED package similar to that of FIG. 2 for an embodiment in which the light filtering material is disposed with increased loading along the periphery of the cover structure compared to the central portion of the cover structure. [Figure 6]

[0020] 6 is a cross-sectional view of an LED package similar to that of FIG. 5 for an embodiment in which the light filtering material is disposed at an increased loading along a central portion of the cover structure compared to the periphery of the cover structure. [Figure 7]

[0021] 6 is a cross-sectional view of an LED package similar to that of FIG. 5 for an embodiment in which the light filtering material is concentrated near the top surface of the cover structure. [Figure 8]

[0022] 8 is a cross-sectional view of an LED package similar to that of FIG. 7 for an embodiment in which the light filtering material is concentrated near the bottom surface of the cover structure. [Figure 9]

[0023] 8 is a cross-sectional view of an LED package similar to that of FIG. 7 for an embodiment in which the light filtering material is concentrated vertically along the central portion of the cover structure. [Figure 10]

[0024] FIG. 10A is a cross-sectional view of an LED package similar to that of FIG. 3 and including photochromic particles according to embodiments disclosed herein.

[0025] FIG. 10B is a cross-sectional view illustrating the response of photochromic particles to increasing light intensity. [Figure 11]

[0026] FIG. 11A is a plot illustrating the typical luminous decay over the lifetime of a blue LED chip.

[0027] FIG. 11B is a cross-sectional view of a cover structure with photochromic particles receiving light from the most intense portion of the plot in FIG. 11A.

[0028] FIG. 11C is a cross-sectional view of the cover structure of FIG. 11B, with photochromic particles receiving light from the plotted portion of FIG. 11A at a reduced intensity compared to FIG. 11B.

[0029] FIG. 11D is a cross-sectional view of the cover structure of FIGS. 11B and 11C in which the photochromic particles receive light at a lower intensity from the plot portion of FIG. 11A compared to FIGS. 11B and 11C. DETAILED DESCRIPTION OF THE INVENTION

[0014]

[0030] The embodiments described below represent the information necessary to enable one skilled in the art to realize the embodiments and illustrate the best modes for achieving them. Upon reading the following description in conjunction with the accompanying drawings, one skilled in the art will understand the concepts of the present disclosure and will recognize applications of these concepts not specifically addressed herein. These concepts and applications should be understood to be within the scope of this disclosure and the appended claims.

[0015]

[0031] In this specification, terms such as first, second, etc. may be used to describe various elements, but it will be understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element, without departing from the scope of the present disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0016]

[0032] When an element such as a layer, region, or substrate is referred to as being "on" or extending "onto" another element, it will be understood that the element may be directly on or extending directly onto the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly on" or extending "directly onto" another element, there are no intervening elements. Similarly, when an element such as a layer, region, or substrate is referred to as being "on" or extending "onto" another element, it will be understood that the element may be directly on or extending directly onto the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly on" or extending "directly onto" another element, there are no intervening elements. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, the element may be directly connected or coupled to the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

[0017]

[0033] Relative terms such as "lower" or "above" or "upper" or "bottom" or "horizontal" or "vertical" may be used herein to describe the relationship of one element, layer, or region to another element, layer, or region, as illustrated in the figures. It will be understood that these terms, and those discussed above, are intended to encompass various orientations of the device in addition to the orientation depicted in the figures.

[0018]

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, it will be understood that the terms "comprises," "comprising," "including," and / or "comprising," as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0019]

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Furthermore, it will be understood that terms used herein should be interpreted as having a meaning consistent with the meaning in the context of this specification and the related art, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0020]

[0036] Embodiments are described herein with reference to schematic diagrams of embodiments of the present disclosure. As such, actual dimensions of layers and elements may vary, and variations from the shapes of the schematic diagrams are expected, for example, as a result of manufacturing techniques and / or tolerances. For example, regions illustrated or described as square or rectangular may have rounded or curved features, and regions depicted as straight lines may have irregularities. Accordingly, regions illustrated in the drawings are schematic, and their shapes are not intended to illustrate the exact shape of a region of a device or to limit the scope of the present disclosure. Additionally, the size of structures or regions may be exaggerated relative to other structures or regions for illustrative purposes and, therefore, are provided to illustrate the general structure of the present subject matter and may or may not be drawn to scale. Elements common between figures may be illustrated with common element numbers herein and may not be described again later.

[0021]

[0037] The present disclosure relates to solid-state lighting devices including light-emitting diodes (LEDs), and more particularly to a material arrangement in a cover structure for an LED that tailors light emission. The material arrangement includes light-filtering particles or ionic species integrated within the material of the cover structure that covers an LED chip within an LED package. The light-filtering material can be configured to selectively filter one or more portions of light provided by the LED chip and / or by the light-emitting material within the LED package. Dispersing the light-filtering material within the cover structure provides protection and mechanical support for the light-filtering material. Additionally, the arrangement and concentration of the light-filtering material within the cover structure may be varied horizontally and / or vertically to tailor the light emission pattern of the corresponding LED package. The material arrangement includes light-filtering species incorporated at the atomic level within the cover structure. A further material arrangement includes photochromic particles configured to proportionally scatter light based on the relative intensity of the light from the LED chip.

[0022]

[0038] Before delving into the specific details of various aspects of the present disclosure, an overview of the various elements that may be included in an exemplary LED package of the present disclosure is provided for context. An LED chip typically comprises an active LED structure or region that may have a number of different semiconductor layers arranged in different ways. The fabrication and operation of LEDs and their active structures are generally known in the art and will only be briefly discussed herein. The layers of the active LED structure can be fabricated using known processes, with a suitable process being fabrication using metal organic chemical vapor deposition. The layers of the active LED structure can comprise many different layers, and typically comprise an active layer sandwiched between n-type and p-type oppositely doped epitaxial layers, all of which are formed successively on a growth substrate. It is understood that the active LED structure may also include additional layers and elements, including, but not limited to, buffer layers, nucleation layers, super lattice structures, undoped layers, cladding layers, contact layers, current-spreading layers, light extraction layers, and elements. The active layer may comprise a single quantum well, multiple quantum wells, a double heterostructure, or a super lattice structure.

[0023]

[0039] The active LED structure can be fabricated from different material systems, some of which are Group III nitride-based. Group III nitrides refer to semiconductor compounds formed from nitrogen (N) and elements from Group III of the periodic table, usually aluminum (Al), gallium (Ga), and indium (In). Gallium nitride (GaN) is a common binary compound. Group III nitrides also refer to ternary and quaternary compounds such as aluminum gallium nitride (AIGaN), indium gallium nitride (InGaN), and aluminum indium gallium nitride (AlInGaN). Other material systems include silicon carbide (SiC), organic semiconductor materials, and other III-V systems such as gallium phosphide (GaP), gallium arsenide (GaAs), and related compounds. The active LED structure can be grown on a growth substrate, which can include many materials, such as sapphire, SiC, aluminum nitride (AlN), and GaN.

[0024]

[0040] Different embodiments of the active LED structure can emit light of different wavelengths, depending on the configuration of the active layer, n-type layer, and p-type layer. In some embodiments, the active LED structure emits blue light with a peak wavelength range of approximately 430 nanometers (nm) to 480 nm. In other embodiments, the active LED structure emits green light with a peak wavelength range of 500 nm to 570 nm. In other embodiments, the active LED structure emits red light with a peak wavelength range of 600 nm to 650 nm. Other wavelength ranges include the ranges of 400 nm to approximately 430 nm and / or the ranges of 480 nm to 500 nm, or any wavelength in the range of 400 nm to 750 nm, among others. In certain embodiments, the active LED structure can be configured to emit light outside the visible spectrum, including one or more portions of the ultraviolet (UV) spectrum. The UV spectrum is typically divided into three wavelength range categories, designated by the letters A, B, and C. Thus, UV-A light is typically defined as having a peak wavelength range of 315 nm to 400 nm, UV-B is typically defined as having a peak wavelength range of 280 nm to 315 nm, and UV-C is typically defined as having a peak wavelength range of 100 nm to 280 nm. UV LEDs are of particular interest for applications related to disinfection of microorganisms, especially in air, water, and on surfaces. In other applications, UV LEDs may also be provided with one or more luminescent materials to provide the LED package with an aggregate emission having a broad spectrum and improved color quality for visible light applications.

[0025]

[0041] As used herein, a layer or region of a light-emitting device may be considered "transparent" if at least 80% of the emitted radiation impinging on that layer or region passes through that layer or region and exits. Additionally, as used herein, a layer or region of an LED may be considered "reflective" or embody a "mirror" or "reflector" if at least 80% of the emitted radiation impinging on that layer or region is reflected. In some embodiments, the emitted radiation comprises visible light, such as blue and / or green LEDs, with or without luminescent materials. In other embodiments, the emitted radiation may comprise non-visible light. For example, in the context of GaN-based blue and / or green LEDs, silver (Ag) may be considered a reflective material (e.g., at least 80% reflective). For UV LEDs, appropriate materials may be selected to achieve desirable, in some embodiments, high reflectivity and / or desirable, in some embodiments, low absorption. In certain embodiments, a "light-transmitting" material may be configured to transmit at least 50% of the emitted radiation of a desired wavelength.

[0026]

[0042] The present disclosure may be useful for LED chips having various geometries, including flip-chip geometries. The flip-chip structure of an LED chip typically includes anode and cathode connections provided from the same side or face of the LED chip. The anode and cathode sides are typically structured as the mounting face of the LED chip for flip-chip mounting to another surface, such as a printed circuit board. In this regard, the anode and cathode connections on the mounting face serve to mechanically and electrically bond the LED chip to the other surface. When flip-chip mounted, the opposite side or face of the LED chip coincides with the light-emitting surface oriented in the intended direction of light emission. In certain embodiments, when flip-chip mounted, the growth substrate of the LED chip may form and / or be adjacent to the light-emitting surface. During chip fabrication, active LED structures may be epitaxially grown on the growth substrate.

[0027]

[0043] According to aspects of the present disclosure, an LED package may include one or more elements, such as a cover structure with a wavelength-converting luminescent material or phosphor, an encapsulant, a light-altering material, a lens, and electrical contacts, among others, provided with one or more LED chips. In certain aspects, the LED package may include a support structure or member, such as a submount or lead frame. A support structure may refer to a structure of the LED package that supports one or more other elements of the LED package, including, but not limited to, the LED chip and the cover structure. In certain embodiments, the support structure may include a submount on which the LED chip is mounted. Suitable materials for the submount include, but are not limited to, ceramic materials such as aluminum oxide or alumina, AlN, or organic insulators such as polyimide (PI) or polyphthalamide (PPA). In other embodiments, the submount may comprise a printed circuit board (PCB), sapphire, Si, or any other suitable material. For PCB embodiments, different types of PCBs can be used, such as standard FR-4 PCBs, metal core PCBs, or any other type of PCB. In still further embodiments, the support structure may embody a leadframe structure. Aspects of the present disclosure are provided in the context of a support structure for LED chips that may emit light in any number of wavelength ranges, including wavelengths within the UV and / or visible light spectrum.

[0028]

[0044] Light-modifying materials can be disposed inside an LED package to reflect or otherwise redirect light from one or more LED chips into a desired emission direction or pattern. As used herein, light-modifying materials can include many different materials, including light-reflecting materials that reflect or redirect light, light-absorbing materials that absorb light, and materials that act as thixotropic agents. As used herein, the term "light-reflective" refers to materials or particles that reflect, refract, scatter, or otherwise redirect light. For light-reflecting materials, the light-modifying material may include at least one of fused silica, fumed silica, titanium dioxide (TiO2), or metal particles suspended in a binder such as silicone or epoxy. For light-absorbing materials, the light-modifying material may include at least one of carbon, silicon, or metal particles suspended in a binder such as silicone or epoxy. Light-reflecting and light-absorbing materials may comprise nanoparticles. In certain embodiments, the light-modifying material may generally comprise a white color to reflect and redirect light. In other embodiments, the light-modifying material may generally have an opaque or black color to absorb light and enhance contrast.

[0029]

[0045] The LED chip may also be coated or otherwise positioned to emit light toward one or more luminescent materials (also referred to herein as lumiphores), such as phosphors, such that at least a portion of the light from the LED chip is absorbed by the one or more lumiphores and converted to one or more different wavelength spectra according to the characteristic emission from the one or more lumiphores. In this regard, the at least one lumiphore, which receives at least a portion of the light generated by the LED source, may re-emit light having a different peak wavelength than the LED source. The LED source and one or more luminescent materials may be selected so that their combined output results in light having one or more desirable characteristics, such as color, color point, intensity, etc. In certain embodiments, the overall emission of the LED chip, optionally in combination with one or more luminescent materials, may be arranged to provide cool white, neutral white, or warm white light, for example, within a color temperature range of 2500 Kelvin (K) to 10,000 K. In certain embodiments, luminescent materials having peak wavelengths of cyan, green, amber, yellow, orange, and / or red may be used. In some embodiments, the combination of the LED chip and one or more lumiphores (e.g., phosphors) generally emits a combination of white light. The one or more phosphors may be yellow (e.g., YAG:Ce), green (e.g., LuAg:Ce), and red (e.g., Ca i-x-y Sr x EU y AlSiN3) light-emitting phosphors, and combinations thereof.

[0030]

[0046] The luminescent materials described herein may be or include one or more of phosphors, scintillators, luminescent inks, quantum dot materials, day glow tape, and the like. The luminescent materials may be provided by any suitable means, such as, for example, dispersion in a host material or an encapsulant material. In certain embodiments, the luminescent materials may be downconverting or upconverting, or a combination of both downconverting and upconverting materials may be provided. In certain embodiments, multiple different (e.g., compositionally different) luminescent materials arranged to produce different peak wavelengths may be arranged to receive the emitted light from one or more LED chips. In certain embodiments, one or more luminescent materials may be arranged in a substantially uniform manner on or above one or more surfaces of the LED chip. In other embodiments, one or more luminescent materials may be arranged in a non-uniform manner with respect to one or more of material composition, concentration, and thickness on or above one or more surfaces of the LED chip. In certain embodiments, the fill percentage of one or more luminescent materials may vary relative to one or more outer surfaces of the LED chip. In certain embodiments, one or more luminescent materials may be patterned relative to one or more surfaces of the LED chip to include one or more stripes, dots, curves, or polygonal shapes. In certain embodiments, multiple luminescent materials may be disposed in different discrete regions or layers on or above the LED chip.

[0031]

[0047] In certain embodiments, one or more luminescent materials may be provided as at least a part of a wavelength converting element or cover structure of an LED package. The wavelength converting element or cover structure may include a phosphor-in-glass or phosphor-in-ceramic arrangement. A phosphor-in-glass or phosphor-in-ceramic arrangement may be formed by mixing phosphor particles with glass frit or ceramic material, pressing the mixture into a planar shape, and firing or sintering the mixture to form a hardened structure that can be cut or separated into individual wavelength converting elements. For certain phosphor-in-glass arrangements, multiple sheets of precursor material, such as glass frit and a corresponding binder, may be stacked and fired together. The wavelength converting element may be attached to one or more LED chips, for example, using a layer of transparent adhesive. In certain embodiments, the layer of transparent adhesive may include silicone having a refractive index in the range of about 1.3 to about 1.6, which is less than the refractive index of the LED chip on which the wavelength converting element is disposed.

[0032]

[0048] Aspects of the present disclosure may include specific arrangements of materials that can be provided within a cover structure of an LED package to modify and / or improve light-emitting characteristics. Such a cover structure may include a rigid and mechanically robust structure disposed over one or more LED chips within the LED package. The cover structure may be formed from a host material, such as glass or ceramic, glass frit and / or laminated sheets of glass frit, or various ceramic materials. As further described with respect to certain embodiments, the luminescent material may be provided as a separate layer on the cover structure, or the luminescent material may be embedded within the cover structure. The cover structure may be configured to protect underlying portions of the LED package from environmental exposure, thereby providing a more robust LED package suitable for applications requiring high output with improved light intensity, contrast, and reliability, such as automotive interior and exterior applications. Light-filtering materials for modifying and / or improving light-emitting characteristics may include light-filtering particles or ionic species configured to selectively filter specific wavelengths of light. In various aspects, the light-filtering material may include, but is not limited to, inorganic materials, dielectric materials, and metallic materials. Exemplary light-filtering materials may embody molecules, ions, particles, and / or scattering particles of various materials. In yet another example, light-filtering ionic species are incorporated into the material of the cover structure at the atomic level. Light-filtering ionic species may include chromium-based materials, cadmium-based materials, and / or cobalt-based materials, among others.

[0033]

[0049] As used herein, light filtering materials and / or particles may include various distributions, particle sizes, and / or configurations with refractive index differences from the surrounding cover structure material, which collectively provide the ability to pass certain wavelengths of light while reflecting, redirecting, or absorbing other wavelengths of light. In various configurations, light filtering materials as described herein may form one or more of a bandpass filter, a highpass filter, a lowpass filter, and a notch or bandstop filter for light passing through the corresponding cover structure. A bandpass filter may be configured to pass wavelengths within a certain range and reflect wavelengths outside of a certain range. A lowpass filter may pass wavelengths below a certain value and reflect wavelengths above that value. A highpass filter may pass wavelengths above a certain value and reflect wavelengths below that value. Finally, a notch or bandstop filter may reflect wavelengths within a certain range and pass wavelengths outside of a certain range. Specific placement of light filtering material within the LED package is disclosed that can reflect unconverted light (e.g., light from the LED chip) back to the luminescent material, thereby improving light conversion efficiency and potentially reducing the thickness of the luminescent material. Such reduction in thickness and corresponding amount of luminescent material can further help reduce heat generation from the luminescent material during operation.

[0034]

[0050] 1A-9 are discussed below in the general context of light-filtering materials. The disclosed principles are similarly applicable to any light-filtering material, such as light-filtering ionic species and / or light-filtering particles, that may be incorporated within the cover structure. In this regard, the locations of light-filtering materials described below with respect to FIGS. 1A-9 may represent the locations of light-filtering ionic species within a host material or matrix, such as a glass or ceramic, of the cover structure, or the locations of light-filtering particles that may be dispersed within the cover structure. In yet another embodiment, the light-filtering materials described below with respect to FIGS. 1A-9 may include multiple types of filtering materials and / or particles configured to provide different filtering characteristics from one another.

[0035]

[0051] FIG. 1A is a cross-sectional view of an LED package 10 including an LED chip 12 with a cover structure 14 including a light-filtering material 16 according to embodiments disclosed herein. As illustrated, the light-filtering material 16 is embedded or integrated within the host material of the cover structure 14. For example, the base material of the cover structure 14 may include glass, with the light-filtering material 16 dispersed throughout the glass. By incorporating the light-filtering material 16 within the cover structure 14 rather than as a separate film or coating, the material of the cover structure 14 may effectively provide encapsulation and environmental protection for the light-filtering material 16. In certain embodiments, the LED package 10 may further include a light-emitting material 18 disposed in a light-receiving position relative to the LED chip 12. The light-emitting material 18 may be provided as a coating or layer on the cover structure 14, such as a silicone layer embedded with one or more types of phosphor particles. In other embodiments, the light-emitting material 18 may embody a preformed and cured structure attached to the LED chip 12 and / or the cover structure 14. Such pre-formed structures may include phosphor plate-in-glass or ceramic phosphor plate arrangements.

[0036]

[0052] FIG. 1B is an exploded view of the LED package 10 of FIG. 1A with an overlaid light spectrum plot illustrating exemplary filtering characteristics. The LED chip 12 is configured to generate light at a first peak wavelength 12′ or in a first peak wavelength range. A superimposed arrow of the first peak wavelength 12′ and a corresponding spectral plot with only the first peak wavelength 12′ are provided above the LED chip 12 to indicate the light propagation direction and the corresponding spectrum of the light before reaching the luminescent material 18. After passing through the luminescent material 18, a portion of the first peak wavelength 12′ is converted to light at a second peak wavelength 18′ or in a second peak wavelength range. Therefore, the size of the superimposed arrow of the first peak wavelength 12′ is reduced above the luminescent material 18, and another arrow representing the second peak wavelength 18′ is shown. Additionally, the corresponding spectral plot above the luminescent material 18 illustrates the reduced intensity of the first peak wavelength 12′ along with the presence of the second peak wavelength 18′. In this example, the light filtering material 16 of the cover structure 14 is configured to selectively filter light of the first peak wavelength 12′. Thus, the light exiting the cover structure 14 may be primarily in the second peak wavelength range 18′, such as at least 95%, at least 97%, or at least 99% of the total light emission. Such an LED package 10 may be referred to as a saturated emitter package, in which the total light emission is primarily provided by converted light from the light-emitting material 18. For a range of values ​​for the first peak wavelength, the light filtering material 16 may filter the entire first peak wavelength range or a portion, or subset, of the first peak wavelength range. In a specific example, the first peak wavelength may be in the range of 430 nm to 480 nm, and the second peak wavelength is in the range of 500 to 650 nm.

[0037]

[0053] In other embodiments, the LED package 10 may not embody a so-called saturated emitter package. Instead, the light filtering material 16 may be applied to selectively dim the overall light emission, particularly for end applications where the light intensity needs to be below a threshold brightness level. In this manner, the light filtering material 16 may be provided at a reduced loading compared to saturated emitter embodiments, thereby filtering only a controlled portion of the overall light. In such an example, the light filtering material 16 may be configured to filter a specific percentage of the first peak wavelength 12′, a specific percentage of the second peak wavelength 18′, or both.

[0038]

[0054] In other embodiments, the light filtering material 16 may be configured to filter only a subset, i.e., a portion, of the first peak wavelength range and / or the second peak wavelength range. For example, the first peak wavelength may be in the range of 430 nm to 480 nm, with the corresponding edge of the emission spectrum extending below 400 nm and into the UV emission. In certain embodiments, the light filtering material 16 may be configured to selectively filter wavelengths below 400 nm while passing other wavelengths. In another example, the light filtering material 16 may be configured to selectively filter wavelengths above 700 nm.

[0039]

[0055] In other embodiments, the light filtering material 16 may embody multiple filtering types that selectively filter different peak wavelength ranges. For example, the light filtering material 16 may include a first filtering type that selectively filters wavelengths below 400 nm and a second filtering type that selectively filters wavelengths above 700 nm. In another example, the first and / or second filtering types may selectively filter specific wavelength bands within a broader range from 400 nm to 700 nm.

[0040]

[0056] Figure 2 is a cross-sectional view of an LED package 20 similar to the LED package 10 of Figure 1, illustrating additional package elements. In Figure 2, the LED chip 12 has a flip-chip orientation such that the anode contact 22 and the cathode contact 24 are accessible from the same side of the LED chip 12 for flip-chip mounting to a submount 26. The submount 26 typically includes corresponding electrical traces for routing electrical connections to the LED chip 12. Although a single LED chip 12 is illustrated, multiple LED chips 12 can be mounted on the submount 26, each with its own cover structure 14, or under a common cover structure 14 for multiple LED chips.

[0041]

[0057] As illustrated in FIG. 2 , a light-modifying layer 28 can be provided on the submount 26 and on the side edges surrounding the LED chip 12. The light-modifying layer 28 may include a light-reflecting and / or light-refractive material that effectively redirects laterally propagating light toward a desired light emission direction, such as through the cover structure 14. In certain embodiments, the light-modifying layer 28 may surround the side edges of the light-emitting material 18. In this manner, the cover structure 14 forms the light-emitting surface of the LED package 20, and light propagating laterally from either the LED chip 12 or the light-emitting material 18 may be redirected for interaction with the light-filtering material 16 of the cover structure 14. In yet another embodiment, the light-modifying layer 28 may surround the side edges of the cover structure 14 to form an emission pattern exiting the LED package 20. As illustrated, a portion of the cover structure 14 may be positioned to protrude above the light-modifying material 28. In this manner, clearance may be provided to account for manufacturing variations and to avoid accidentally forming the light-modifying material 28 on the top surface of the cover structure 14. For light-reflecting embodiments, light modifying layer 28 may have a predominantly white color. Alternatively, light modifying material 28 may be provided with a predominantly black color to enhance the contrast of light passing through cover structure 14. In certain embodiments, light modifying material 28 described with respect to FIG. 2 may be implemented with any of the following embodiments described with respect to FIGS. 3-10A.

[0042]

[0058] 3 is a cross-sectional view of an LED package 30 similar to LED package 20 of FIG. 2 for an embodiment in which luminescent material 18 is provided as luminescent particles dispersed within cover structure 14 along with light-filtering material 16. In this manner, particles of luminescent material 18 and light-filtering material 16 may be simultaneously embedded and mixed together within cover structure 14. In certain embodiments, such an arrangement may avoid the need for a separate layer or structure for luminescent material 18. Accordingly, cover structure 14 may embody a phosphor-in-glass structure that also exhibits light-filtering properties.

[0043]

[0059] 4 is a cross-sectional view of an LED package 30 similar to the LED package 20 of FIG. 2 for an embodiment in which the LED package 30 does not include a light-emitting material. Accordingly, a cover structure 14 comprising a light filtering material 16 may be provided over the LED chip 12 to filter a portion of the light generated by the LED chip 12. For example, the light filtering material 16 may filter the edges of the emission spectrum below 400 nm or above 700 nm, depending on the embodiment. In other embodiments, the light filtering material 16 may be disposed at a fill amount that reduces the brightness of the emitted peak wavelength, effectively dimming the LED chip 12 to a target brightness.

[0044]

[0060] 5-9 illustrate various embodiments in which the placement of light filtering material 16 within cover structure 14 is varied horizontally or vertically to provide various light emission patterns. According to aspects disclosed herein, light filtering material 16 can be dispersed or embedded within cover structure 14, thereby varying the local concentration of light filtering material 16 within cover structure 14 to tailor the light emission to a target application. In the case of glass for the base material of cover structure 14, a precursor sheet of glass frit may be disposed with different localized regions of light filtering material 16 and / or with a sheet of different glass frit with varying concentrations of light filtering material 16. In the case of ceramic, the base material of cover structure 14 employs a precursor sheet of ceramic material.

[0045]

[0061] FIG. 5 illustrates a cross-sectional view of an LED package 34 similar to the LED package 20 of FIG. 2 for an embodiment in which the light filtering material 16 is disposed at an increased loading along the periphery of the cover structure 14 compared to the central portion of the cover structure 14. Such an arrangement can help reduce color mixing nonuniformity resulting from light from the LED chip 12 passing through a decreasing amount of the light emitting material 18 along the periphery of the LED package 34. In certain embodiments, the central region of the cover structure 14 is free of the light filtering material 16, which can promote increased light emission in the desired direction of light emission. As illustrated, the cover structure 14 may have a graded distribution of the light filtering material 16 from the periphery to the central region. For example, if the light filtering material 16 comprises a light filtering ionic species, the ionic species can diffuse during formation of the cover structure 14, so that a distinct boundary need not necessarily exist. Additionally, a graded distribution of light filtering particles can also be provided. In other embodiments, a distinct boundary of the light filtering material within the cover structure 14 can be defined.

[0046]

[0062] FIG. 6 is a cross-sectional view of an LED package 36 similar to the LED package 34 of FIG. 5 for an embodiment in which the light filtering material 16 is disposed with increased packing along the central portion of the cover structure 14 compared to the periphery of the cover structure 14. Such an arrangement may be implemented to reduce the intensity of the overall light emission of the LED package 36 by spatially reducing the areas of highest light intensity. In addition, the light filtering material 16 may be absent from areas at or near the periphery of the cover structure 14. Similar to what was described above with respect to FIG. 5, the light filtering material 16 may form a graduated distribution or a distinct boundary within the cover structure 14.

[0047]

[0063] FIG. 7 is a cross-sectional view of an LED package 38 similar to the LED package 34 of FIG. 5 for an embodiment in which the light filtering material 16 is concentrated near the top surface of the cover structure 14. In this manner, a portion of the cover structure 14 that does not include the light filtering material 16 is disposed between the light filtering material 16 and the LED chip 12. Such an arrangement can be advantageous for directing heat generated by the light filtering material 16 away from the LED chip 12. As described above, stacking sheets of precursor material to form the cover structure 14 can vary the concentration of the light filtering material 16 vertically. While FIG. 7 illustrates the luminescent material 18, the luminescent material 18 may be omitted in certain embodiments.

[0048]

[0064] FIG. 8 is a cross-sectional view of an LED package 40 similar to LED package 38 of FIG. 7 for an embodiment in which light filtering material 16 is concentrated near the bottom surface of cover structure 14. In FIG. 8, light filtering material 16 is disposed near LED chip 12. Similar to that described above with respect to FIG. 5, light filtering material 16 can form a graduated distribution or a distinct boundary within cover structure 14. In certain embodiments, light emitting material 18 of FIG. 3 may be integrated within cover structure 14.

[0049]

[0065] 9 is a cross-sectional view of an LED package 42 similar to LED package 38 of FIG. 7 for an embodiment in which light filtering material 16 is vertically concentrated along a central portion of cover structure 14. Similar to that described above with respect to FIG. 5, light filtering material 16 can form a graduated distribution or a distinct boundary within cover structure 14. In certain embodiments, light emitting material 18 of FIG. 3 may be integrated within cover structure 14.

[0050]

[0066] According to certain aspects of the present disclosure, photochromic particles may be incorporated into the LED package. The photochromic particles are arranged to apply flux-dependent photoactivated chemistry based on the relative intensity of light emitted from the LED chip. For example, when the light from the LED chip is at a high relative intensity, the photochromic particles may be configured to scatter a greater amount of light. Conversely, when the light from the LED chip is provided at a lower relative intensity, the photochromic particles may be configured to scatter a smaller amount of light. Increased scattering may decrease the relative amount of light emitted from the LED package, while decreased scattering may increase the relative amount of light emitted from the LED package. In this way, the intensity of the LED chip will decrease over its lifetime, but the effect of the photochromic particles may level off or reduce the rate of this decrease. Exemplary photochromic materials for the photochromic particles include organic compounds such as spiropyrans and metal dithizonates, silicate photochromic glasses containing silver halide microcrystals, such as silver bromide (AgBr) or silver chloride (AgCl), and activated crystals of alkali metal halide compounds.

[0051]

[0067] FIG. 10A is a cross-sectional view of an LED package 44 including photochromic particles 46 according to aspects disclosed herein, similar to the LED package 30 of FIG. 3 . In certain embodiments, the photochromic particles 46 may be dispersed or otherwise embedded within the cover structure 14. However, in other embodiments, the photochromic particles 46 may be present in other portions of the LED package 44, such as within the encapsulant, if the cover structure 14 is omitted. As described above, the photochromic particles 46 may be configured to scatter light from the LED chip 12 in proportion to the intensity of light provided by the LED chip 12. In certain embodiments, particles of the luminescent material 18 may also be incorporated within the cover structure 14 along with the photochromic particles 46. In this manner, the photochromic particles 46 may scatter light from the luminescent material 18 in proportion to the intensity of light from the LED chip 12. FIG. 10B is a cross-sectional view illustrating the response of the photochromic particles 46 to increasing light intensity. In Figure 10B, the photochromic particles 46 on the left are illustrated as circles to represent no or minimal light scattering. An increase in light intensity is represented by arrows 48. As light intensity increases, the photochromic particles 46' increase scattering. For purposes of illustration, the photochromic particles 46' with increased scattering are represented as stars in Figure 10B.

[0052]

[0068] FIG. 11A is a plot illustrating typical light attenuation over the lifetime of a blue LED chip. The y-axis represents percent luminous flux, and the x-axis represents time in hours. As illustrated, at an initial time of 1,000 hours, the percent luminous flux is nearly 100%. The luminous flux gradually decays, dropping below about 95% near 10,000 hours and decaying more rapidly between 10,000 and 100,000 hours. By providing photochromic particles 46 that variably scatter light based on their relative intensity, the attenuation associated with the LED chip, as illustrated in FIG. 11A, can be mitigated in the overall LED package emission. FIG. 11A includes markers overlaid on the images in FIGS. 11B, 11C, and 11D, each representing an exemplary response of photochromic particles 46, 46′ within the cover structure 14 to various light intensities. FIG. 11B corresponds to the portion of the plot in FIG. 11A with the highest intensity or luminous flux. FIG. 11C corresponds to the portion of the plot in FIG. 11A where the intensity is reduced relative to FIG. 11B. Finally, FIG. 11D corresponds to the portion of the plot in FIG. 11A where the intensity is reduced compared to FIGS. 11B and 11C. Thus, the photochromic particles 46, 46' exhibit the highest amount of light scattering in FIG. 11B, reduced light scattering in FIG. 11C, and little or no light scattering in FIG. 11D. Thus, as the light intensity from the LED chip attenuates, the photochromic particles 46, 46' respond by scattering less light, thereby allowing more light to pass through the cover structure 14 without being backscattered. In various embodiments, the photochromic particles 46, 46' may be provided alone or in combination with the light filtering material 16 described above with respect to FIGS. 1A through 9.

[0053]

[0069] It is contemplated that any of the foregoing aspects and / or various separate aspects and features described herein may be combined to further advantage. Any of the various embodiments disclosed herein may be combined with one or more of the other disclosed embodiments, unless indicated to the contrary herein.

[0054]

[0070] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure, and all such improvements and modifications are considered to be within the scope of the concepts disclosed herein and the following claims.

Claims

1. 1. A light emitting diode (LED) package comprising: A submount and at least one LED chip on the submount, the at least one LED chip configured to produce light in a first peak wavelength range; a cover structure on the at least one LED chip, the cover structure comprising a plurality of light filtering materials integrated therein, the light filtering materials configured to reduce light emissions of specific wavelengths exiting the cover structure; and An LED package comprising:

2. 10. The LED package of claim 1, wherein the plurality of light filtering materials comprises a plurality of light filtering particles.

3. 10. The LED package of claim 1, wherein the plurality of light-filtering materials comprises a plurality of light-filtering ionic species incorporated within a host material of the cover structure.

4. 10. The LED package of claim 1, wherein the light filtering material is configured to reduce the amount of light within at least a portion of the first peak wavelength range that exits the cover structure without wavelength-converting the light in the first peak wavelength range within the cover structure.

5. 10. The LED package of claim 1, wherein the cover structure comprises glass, and the plurality of light filtering materials are embedded inside the glass.

6. 10. The LED package of claim 1, further comprising a luminescent material between the cover structure and the at least one LED chip, the luminescent material being configured to convert a portion of the light in the first peak wavelength range into light in a second peak wavelength range.

7. 7. The LED package of claim 6, wherein the light filtering material is configured to reduce the amount of light within at least a portion of the first peak wavelength range that exits the cover structure more than the amount of light within the second peak wavelength range.

8. 7. The LED package of claim 6, wherein the light filtering material is configured to reduce the amount of light within at least a portion of the second peak wavelength range that exits the cover structure.

9. 10. The LED package of claim 1, wherein the light filtering material is configured to reduce light emissions at wavelengths less than 400 nanometers that exit the cover structure.

10. 10. The LED package of claim 1, wherein the light filtering material is configured to reduce light emissions at wavelengths greater than 700 nanometers that exit the cover structure.

11. 10. The LED package of claim 1, further comprising luminescent material particles dispersed within the cover structure along with the light filtering material.

12. 10. The LED package of claim 1, wherein the light filtering material is disposed in a higher concentration near a periphery of the cover structure than in a central portion of the cover structure.

13. 10. The LED package of claim 1, wherein the light filtering material is disposed in a higher concentration along a central portion of the cover structure than near a periphery of the cover structure.

14. 10. The LED package of claim 1, wherein the light filtering material is disposed within the cover structure so that its concentration varies in a direction perpendicular to the LED chip.

15. 10. The LED package of claim 1, wherein the light filtering material comprises at least a first filter type and a second filter type, the second filter type configured to selectively filter a different wavelength range than the first filter type.

16. 1. A light emitting diode (LED) package comprising: A submount and at least one LED chip on the submount; a plurality of photochromic particles disposed on the at least one LED chip, the plurality of photochromic particles configured to variably scatter light from the at least one LED chip based on a relative intensity of light from the at least one LED chip; An LED package comprising:

17. 17. The LED package of claim 16, wherein the plurality of photochromic particles are configured to reduce scattering of the light from the at least one LED chip when the intensity of the light from the at least one LED chip decreases.

18. 17. The LED package of claim 16, further comprising a cover structure on the at least one LED chip, the plurality of photochromic particles being dispersed inside the cover structure.

19. 20. The LED package of claim 18, further comprising light filtering particles dispersed within the cover structure.

20. 20. The LED package of claim 18, further comprising luminescent material particles dispersed within the cover structure.

21. 21. The LED package of claim 20, wherein the plurality of photochromic particles are configured to reduce scattering of the light from luminescent material particles when the intensity of the light from the at least one LED chip decreases.

22. 17. The LED package of claim 16, wherein the plurality of photochromic particles comprises one or more of an organic compound, a silicate photochromic glass containing silver halide microcrystals, and an activated crystal of an alkali metal halide compound.

Images