JP5178714B2 - Lighting device package - Google Patents

Description

  The present invention relates to light emitting devices, and more particularly to the design of optical components of lighting device packages.

  Light emitting diodes (LEDs) can be more efficient if the LED package is properly designed to efficiently extract light generated within the LED package in an operating situation. From the perspective of the device designer, effective light extraction is a challenge to improve the chance that light from the LED die can leave the LED package without having to go through unnecessary reflections inside the LED package. obtain. Multiple design considerations affect the optical path, such as the orientation and position of the optical interface, and the optical properties of the relevant components of the LED package, such as the type of material on either side of the optical interface. Can give. In addition, the propagation of light inside the LED package may include its wavelength, its intensity, LED die size and luminous efficiency, drive current, opacity of the LED package optical elements, temperature conditions inside the LED package, LED package component materials And the refractive index inside the environmental medium, as well as the temperature dependence of the refractive index of the relevant material, for example. Prior art LED packages have at least an LED die and an inclusion lens. In certain LED packages, the lens and encapsulating material are separate or made from different materials. As a result, the LED package can have a die-encapsulant optical interface, an encapsulant-lens optical interface, and a lens-air optical interface.

  In addition to changing the direction of propagation of light emitted by the LED die, the optical interface is a refraction of two media on either side of the optical interface, the wavelength of light, the angle of incidence at the optical interface, and the optical interface. Depending on the rate, the variable part of the light can be reflected and transmitted. Partial reflection and transmission at the optical interface of the LED package can cause a series of repeatedly reflected and transmitted light rays. As a result, certain reflections can stretch the optical path that can increase the likelihood of unwanted light absorption inside the LED package. Furthermore, light can experience total internal reflection (TIR) that can occur depending on the refractive index ratio at a particular angle of incidence. This effect can occur when light propagates through a medium having a first refractive index and strikes an optical interface having a sufficiently thick layer of another medium having a second refractive index less than the first refractive index. . Total internal reflection substantially completely suppresses transmission of light across and far beyond the optical interface. Still further, improper design of the refractive element causes the LED to emit light with potentially impractical spatial light emission characteristics that may include color irregularities or brightness in the light emission pattern due to monochromatic or chromatic aberration. Can be let.

  For example, even in the visible portion of the spectrum, the refractive index of the LED die can vary greatly. Most dies currently in use have a refractive index in the visible spectrum higher than about 1.6. In addition, for example, certain blue and green LED dies have a refractive index of about 2.6 to 2.7. For example, if the environmental medium is air with a refractive index of about 1.0, and if the refractive index of the die is 1.6, the maximum critical angle for total internal reflection can be about 39 degrees relative to the optical interface. However, for other wavelengths, the critical angle can be quite small. Any light that strikes the optical interface at a larger angle can be totally reflected internally.

  Known measures to reduce unwanted reflections are to cover the LED die with a material having a refractive index between the die and the refractive index of the air, or more generally a low refractive index ratio at the optical interface. Is to use a material that gives rise to For example, one or more LED dies can be placed in the center of a hemispherical lens, and the space between the die and the lens can be filled with a transparent encapsulating material. The material and lens for the encapsulating material, among other requirements, such that the common refractive index, for example 1.5, matches the refractive index of the environmental medium, which is stepwise 1.0, for example, the refractive index of the die, for example 2.65. Selected. However, this design requires a relatively large lens size when two or more LED dies are grouped together under one lens. However, for better color mixing, it may be desirable to have multiple LED dies in the same package.

  Some of these principles have been recognized in several publications. For example, US Pat. No. 6,610,598 describes a light emitting diode surface mount device (SMD LED) in which the component typically has a planar surface. According to Snell's law calculations, most of the light cannot be emitted directly from the component due to differences in the refractive index of the epoxy resin and the environment (the refractive index of light in the environment is 1 and the epoxy The refractive index of the resin is 1.5). Light emitting diode surface mount devices include several small or diffractive lenses on the planar surface of the SMD LED, and lenses that expand the critical angle can increase the chance of direct light emission from the light emitting chip, and Increase brightness.

  US Pat. Nos. 6,590,235 and 6,204,523 provide LED components having light emission in the green to near ultraviolet wavelength region. The light emitting semiconductor die is encapsulated using one or more silicone composites that include a hard outer shell, an inner gel or an elastic layer, or both. Silicone materials are stable over temperature and humidity ranges and against exposure to ambient ultraviolet radiation. As a result, LED components advantageously have a long life and do not have “yellowing” attenuation that can reduce the light output from green to near-ultraviolet light.

  US Pat. No. 6,639,360 provides a heat dissipation package for high power radiator devices and electronic components. The electronic component package includes a sealed chamber, a liquid or gel contained in the sealed chamber, at least one electronic component disposed in the sealed chamber in physical and thermal contact with the liquid or gel, and At least one electrical conductor electrically coupled to the electronic component and extending outside the sealed chamber. Electronic components may include one or more combinations of radiators, thermal or optical sensors, resistors, and microprocessors or other semiconductor components.

  US Pat. No. 6,867,929 describes a light source device that is safe for the human eye and that is switched at high speed. The light source device is one or more laser light sources that emit a monochromatic or polychromatic light beam, transmissive, reflective, or these for diffusing the light beam received directly from the laser light source or via an optical focusing system And a collimator that collimates the diffused light bundle emitted from the diffuser.

  U.S. Pat. No. 7,015,516 is a light emitting micro comprising a light emitting diode having a first region of a first conductivity type, a second region of a second conductivity type, and a light emitting pn junction between the first region and the second region. An electronic package is described. The light emitting diode defines a lower contact surface and a mesa projecting upward from the lower contact surface. A first region of the first conductivity type is disposed in the mesa and defines an upper surface of the mesa, and a second region of the second conductivity type defines a lower contact surface that substantially surrounds the mesa. The mesa includes at least one sidewall extending between the top surface of the mesa and the lower contact surface, the sidewall having a roughened surface that optimizes light extraction from the package.

  US Pat. No. 7,023,022 describes a light emitting package that includes a substantially transparent substrate having a first surface and a second surface including a lens. The package also includes a light emitting diode (LED) adapted to emit light having a predetermined wavelength, wherein the LED is secured on a first surface of a substantially transparent substrate. The second surface of the substrate defines the main light emitting surface of the package. The lens on the second surface has a grating pattern that matches a predetermined wavelength of light emitted from the LED to control the light emission shape of the light emitted by the package. The lattice pattern has a radial configuration including a series of concentric circles.

  US Pat. No. 6,921,929 describes a light emitting diode (LED) having an amorphous fluoropolymer encapsulant and a lens. The lens and encapsulating material are made from an amorphous fluoropolymer for LEDs such as UV LEDs or diode lasers. A semiconductor diode die is formed by growing a diode on a substrate layer such as sapphire. The diode die is inverted so that it emits light through the plane of the layer. The amorphous fluoropolymer encapsulant can be formed as a lens to encapsulate the emitting surface of the diode die and form an integral encapsulant / lens. Alternatively, an amorphous fluoropolymer lens can be connected to the encapsulant. Additional connected or individual lenses can also be used. The encapsulant / lens is transparent to ultraviolet light and infrared light. An encapsulation method is also provided.

  U.S. Pat. No. 7,026,657 describes a high brightness LED chip and a method of making it. The light emitting diode chip includes a radioactive region and a window layer. In order to increase the luminous efficiency, the cross-sectional area of the radioactive region is smaller than the cross-sectional area of the window layer available for separating light. The invention further relates to a method of manufacturing a lens structure on the surface of a light emitting component.

  US Pat. No. 6,903,380 describes a method and system for LED packages. The LED package may include a lead frame having an annular contact and a base contact. The LED die can be coupled to the annular and base contacts such that the P-type material portion is electrically connected to the annular contact and the N-type material portion is electrically connected to the base contact. Alternatively, the N-type material portion can be electrically connected to the annular contact and the P-type material portion can be electrically connected to the base contact. The lens can be coupled to the lead frame and the optical material can be located in a cavity defined by the lens, the base contact and the annular contact. The optical material can be a gel, grease, elastic material, non-elastic material, hard material, liquid material, or non-liquid material. The method and system may further include a mounting device, wherein the LED package is mechanically coupled to the mounting device in the form of a socket, bayonet, or screw. The method and system may further include a strip that includes an array of annular contacts that are utilized to form an array of LED packages and a carrier strip that includes a receiving device that receives the array of LED packages. The portion of the lens can be coated with or include a photoexcitable material, or the optical material can include a photoexcitable material such that the system emits white light.

  U.S. Pat. No. 6,480,389 discloses a light emitting diode (LED) comprising a heat dissipating structure that fills a heat dissipating fluid coolant in a sealed housing in which at least one LED chip mounted on a metal substrate is disposed. ). The heat dissipating structure is constructed with metal walls upstanding from the metal substrate used to hold the transparent cap of the sealed housing in place. Further, the upright wall surrounds in close proximity to the at least one LED chip so that Joule heat generated therefrom can be quickly spread to the upright wall via the heat dissipating fluid coolant, along the wall. Is diffused to a metal substrate that connects to a larger external heat sink that dissipates heat, thus preventing at least one LED from overheating. Another feature of the present invention is that the transparent cap of the sealed casing is made of a transparent material, and a convex portion that comes into contact with the heat dissipating fluid coolant is formed on the inner surface of the transparent cap. Therefore, when bubbles are present inside the casing due to insufficient filling, they do not exist in the line of sight due to buoyancy. Thus, the possibility of scattering LED light due to the presence of bubbles is prevented.

  U.S. Pat. No. 5,077,587 describes a light emitting diode including an antireflective layer optimization. Improved light output, such as from an LED, is obtained by modifying the combined thickness dimension of the transmissive diffusion mask layer and the anti-reflective coating layer around the window forming the light emitting region.

  US Patent Application Publication No. 2006/0083000 describes a lens for a light emitting diode formed using a material having a refractive index of n, the lens comprising a base portion and a first extending from the base portion. A curved outer peripheral surface, a curved central edge surface extending from the first curved outer peripheral surface, and a curved innermost surface extending from the curved central edge surface. The base portion includes a groove portion that receives the light emitting chip. In the lens, the distance from the center of the base to the point on the curved central edge surface is always smaller than the radius of curvature for the points on the curved central edge surface. The curved centermost surface has a concave shape with respect to the base portion. In addition, the obtuse angle formed between the main axis of the lens and the tangent of the point on the curved central surface is A1, and a straight line connecting the center of the base to the point on the curved central surface and the main axis of the lens And the acute angle is A2, the lens satisfies the formula: A1 + A2 <90 + 1 / since (1 / n).

  US Patent Application Publication No. 2005/0221519 describes a semiconductor light emitting device including a light emitting conversion element and a method for packaging the device. A method of packaging a semiconductor light emitting device includes dispensing a first quantity of encapsulant material into a cavity containing the light emitting device. The first quantity of encapsulant material in the cavity is processed to form a cured upper surface having a selected shape. A luminescence conversion element is provided on the upper surface of the first quantity to be treated of the encapsulating material. The luminescence conversion element includes a wavelength converting material and has a greater thickness in the middle region of the cavity than the portion adjacent to the sidewall of the cavity.

  US Patent Application Publication No. 2004/0079957 describes a high power surface mount light emitting die package. The die package includes a substrate, a reflector plate, and a lens. The substrate can be made from a thermally conductive but electrically insulating material or a material that is both thermally and electrically conductive. In embodiments where the substrate is made from an electrically conductive material, the substrate further includes an electrically insulating and thermally conductive material formed in the electrically conductive material. The substrate has traces that connect to light emitting diodes (LEDs) at the mounting pads. The reflector plate is connected to the substrate and substantially surrounds the mounting pad. The lens substantially covers the mounting pad. In operation, the heat generated by the LED is extracted from the LED by both the substrate (acting as the bottom heat sink) and the reflector plate (acting as the top heat sink). The reflector plate includes a reflective surface for directing light from the LED in a desired direction.

  US Patent Application Publication No. 2004/0041222 describes a high power surface mount light emitting die package. The die package includes a substrate, a reflector plate, and a lens. The substrate is thermally conductive but can be made from an electrically insulating material. The substrate has traces that connect an external electrical power source to a light emitting diode (LED) at the mounting pad. The reflector plate is connected to the substrate and substantially surrounds the mounting pad. The lens is free to move relative to the reflector plate and can be lifted or lowered by an encapsulating material that wets and adheres the lens and is positioned at an optimal distance from the LED chip. The lens can be covered with an optical system that includes an optochemical material that affects the performance of the device. In operation, the heat generated by the LED is extracted from the LED by both the substrate (acting as the bottom heat sink) and the reflector plate (acting as the top heat sink). The reflector plate includes a reflective surface for directing light from the LED in a desired direction.

  International Patent Application Publication No. 2006/021837 describes a light emitting diode system that includes a semiconductor diode disposed in cooperation with electrical contacts, mounting provisions, and optical coupling, where the optical coupling includes at least a Fresnel lens. Yes. The Fresnel lens is further coupled to additional optical elements such as concave or “negative” lenses, and further to reflectors that operate on the principle of total internal reflection. Both the concave lens and the reflector are non-spherical in a preferred form. A single piece plastic cover element is formed in the mounting process, and all three of these optical elements, the Furanel lens, the negative lens and the reflector, are formed in a single plastic piece. In addition, the plastic piece may be configured to include auxiliary systems such as an array index and securing means and a hanger peripheral configuration.

  International Patent Application Publication No. 2005/107420 includes a light source that emits light, a down-conversion material that receives the emitted light and converts the emitted light into transmitted light and backward transmitted light, and backward transmitted light A light emitting device is described that includes an optical device configured to receive and transmit rear transmitted light to the outside of the optical device. The light source is a semiconductor light emitting diode that may include a light emitting diode, a laser diode, or a resonant cavity light emitting diode. Downconversion materials include one of a phosphor or other material that absorbs light in one spectral region and emits light in another spectral region. The optical device or lens includes a light transmissive material.

  However, it is not disclosed how undesirable internal reflections in the lighting device package are reduced. Accordingly, there is a need for new package designs that overcome some of the known design drawbacks.

  This background information is provided to publish information believed by the applicant to be relevant to the present invention. No admission that any of the above information constitutes prior art to the present invention is necessarily intended and should not be so construed.

  An object of the present invention is to provide a lighting device package.

  According to one aspect of the invention, a lighting device package is a composite lens having one or more light emitting elements operably coupled to a substrate and a surface facing the one or more light emitting elements, The compound lens includes at least an internal lens element and an external lens element, the internal lens element has a first refractive index, the external lens element has a second refractive index, and the first refractive index is a second refractive index. An encapsulating material that fills at least a portion of the space, the compound lens defining a space between which the compound lens, the one or more light emitting elements, and the substrate are closed, And an encapsulating material having a third refractive index equal to or greater than the first refractive index.

  According to another aspect of the present invention, a lighting device package, wherein the lighting device package interacts with one or more light emitting elements operably coupled to a substrate and light emitted by the one or more light emitting elements. A compound lens disposed, the compound lens including at least an inner lens element and an outer lens element, the inner lens element having a first refractive index, and the outer lens element having a second refractive index; At least a portion of the space, wherein the first index of refraction is greater than a second index of refraction and the compound lens, the one or more light emitting elements and the substrate define a space closed between them; An illumination device package is provided that includes an encapsulating material to be filled, the encapsulating material having a third refractive index equal to or greater than the first refractive index.

Definitions The term “light emitting element” (LEE) is used in the electromagnetic spectrum, for example in the visible, infrared and / or ultraviolet region, when activated, for example by applying a potential difference across it or passing an electric current. A device that emits radiation in a region or combination of regions. Thus, the light emitting elements can have the properties of monochromatic, pseudo-monochromatic, multicolored, or broadband spectral emission. Examples of light-emitting elements are semiconductor, organic or polymer / polymer light-emitting diodes, optically-excited phosphor-coated light-emitting diodes, optically-excited nanocrystalline light-emitting diodes, or other similar, as can be readily appreciated by those skilled in the art Including equipment. Furthermore, the term light emitting element is used to define a particular device that emits radiation, such as an LED die.

  As used in this document, the term “about” refers to a +/− 10% variation from the rated value. It should be understood that such variations are always included in any value provided in this document, whether specifically referenced or not.

  Unless defined otherwise, all technical and scientific terms used in this document have the same meaning as commonly understood in the technical field to which this invention belongs.

  The present invention is a lighting device package comprising one or more light emitting elements operably coupled to a substrate and, for example, directly via a lens surface facing the one or more light emitting elements, or A compound lens arranged to interact with light emitted by the one or more light emitting elements, such as indirectly through one or more optical elements such as reflectors, diffusers and windows; A lighting device package is provided.

  In general, a composite lens can be formed from one or more lens elements, for example, each element can be a lens layer of an appropriate thickness having a uniform or non-uniform thickness. The refractive index of the outermost lens element of the compound lens is usually less than the refractive index of the innermost lens element, ie, the lens element closest to the light emitting element. The encapsulating material fills a closed space between the compound lens, the substrate and the one or more light emitting elements. The encapsulating material is selected to have a refractive index that is equal to or greater than the innermost lens element of the compound lens, but less than the refractive index of the light emitting element. In general, the refractive index decreases with the distance of each component from the light emitting element to reduce the opportunity for (total) internal reflection of light emitted by the light emitting element in the light emitting element package.

  The present invention may provide a lighting device package with reduced total internal reflection (TIR) when compared to existing package design techniques. In order to promote small total internal reflection, the illuminator package has a number of optical components made of materials that provide the appropriate refractive index. The optical component may generally be formed and arranged to control the propagation of light within the lighting device package, and specifically to control the propagation of light emitted by the light emitting element. A light emitting element package may have one or more light emitting elements, such as LED dies, that emit light under operating conditions. The light emitting elements can be of various types and emit light that can differ in appearance in color and brightness. In accordance with the present invention, the configuration of the lighting device package determines how light from one or more light emitting elements is directed outside the light emitting element package.

  Many light emitting elements such as LED dies, for example, can be made from synthetic materials that can have a high refractive index. In one embodiment, one approach for efficiently guiding light from a light emitting element to an environmental medium outside the light emitting element package is a series of materials, with relatively small discontinuities between the refractive indices of the materials. The light is continuously propagated through a series of materials having: The closer the refractive index of the adjacent material at the optical interface, the smaller the solid angle at which total internal reflection can occur at this interface.

  Light propagation in the lighting device package can also be affected by the type of light emitting element, such as, for example, how the LED die is mechanically and electrically connected to the substrate. It is noted that the light emitting elements can be arranged and operatively connected using a number of different technologies known in the art. For example, the light emitting elements can be wire bonded from the top of the substrate or surface mounted using a ball grid for flip chip. Also, for example, there may be one or more LED dies within a light emitting element.

  As described above, total internal reflection at each optical interface can be reduced, for example, if the refractive index profile across the elements of the compound lens is characterized by a small discontinuity or a small slope. The same considerations apply to the refractive index profile along the entire optical path from one or more light emitting elements to the environmental medium. The compound lens has a plurality of elements, each element having a different refractive index, where the refractive index varies with the distance from the light emitting element to reach the refractive index of the environmental medium. For many embodiments, the environmental medium has a refractive index close to 1.0, such as that of air. If the refractive index of the environmental medium is lower than the refractive index of the light emitting element, the element of the composite lens can be designed to have a refractive index that decreases as the distance from the light emitting element increases.

Compound Lens The compound lens is positioned relative to the substrate so that the compound lens can effectively optically interact with light emitted by one or more light emitting elements. In certain embodiments, the compound lens may be arranged to interact with the emitted light directly, ie through the surface of the lens facing one or more light emitting elements. In certain embodiments of the invention, the compound lens is arranged to interact indirectly with the emitted light, i.e. through one or more reflectors, diffusers, windows and other such elements. Can be done. In certain embodiments of the present invention, the compound lens may be arranged to interact directly and indirectly with the emitted light.

  A compound lens may be formed from two or more elements of materials having different refractive indices. The refractive index of the outermost element of the compound lens is usually less than the refractive index of the material of one or more inner elements.

  In certain embodiments according to the present invention, the composite lens comprises one or a combination of solid, gel, liquid material, encapsulating material, or the like.

  In certain embodiments of the present invention, the outer surface of the light emitting element package has a hemispherical shape and can be defined by a compound lens. Compared to a monolithic structure optical element of similar size and shape but with a uniform composition or uniform optical properties, such a compound lens relates to a lighting device package having two or more light emitting elements. Or, for large area light emitting elements such as LED dies, may provide better light extraction. As a result, improved light extraction may allow lighting device packages with higher light emitting element density.

  In one embodiment of the invention, a hemispherical lens can be used to manufacture a lighting device package that can emit light having a Lambertian radiation pattern. If it is desired that the illuminator package can emit light having other than a Lambertian radiation pattern, the optical components of the compound lens are appropriately formed, or the thickness or relative distance between the optical components is spherical. Are appropriately sized to provide a different optical interface.

  In some embodiments of the invention, the internal radius of the lens cavity is a circular region in which one or more light emitting elements are disposed to obtain an approximate normal incidence angle with respect to light impinging on the internal surface of the internal element of the compound lens. Can be approximately three times the size of In certain embodiments of the present invention, the hemispherical lens may be positioned relative to the substrate such that the light emitting element is positioned near the sphere center of the inner hemispherical lens cavity.

  Conventional lenses and encapsulating materials with the appropriate refractive index typically absorb little visible light and only certain ultraviolet (UV) light, such as PMMA, polycarbonate, nylon, COC, BK7 glass, and silicone And so on. Some of these types of materials can provide resistance to discoloration under prolonged exposure to UV light and an appropriate refractive index range.

  The compound lens can be manufactured in a number of different ways, for example by shot forming or other suitable manufacturing process known to those skilled in the art.

  In certain embodiments of the present invention, two, three, or more element lenses can be manufactured using a multi-stage shot forming process. For example, two-stage shot forming can be used to manufacture components that provide additional mechanical engagement elements. The engagement element can be formed in a mold forming process and provides subsequent mechanical stability by locking the two components of the compound lens with respect to each other. The type of engagement can be either destructive or non-destructively releasable joints depending on the shape of the engagement element, the nature of the material used and the nature of the molding process.

  Generally, shot-formed components increase the geometric complexity of component parts or subcomponents when formed. As is well known, factors such as delamination or other undesirable stress-inducing effects in manufacturing, for example due to different coefficients of thermal expansion between mold materials, can determine the outcome of another manufacturing. In order to provide individual components with the desired refractive index, compound lenses can be manufactured from varying grades of the same type of material, such as, for example, a particular silicone.

  As is known, the manufacture of composite optical components requires control of the inclusion of undesirable types and quantities in the composite element and at the interface between elements.

  It is noted that other types of mold forming processes can also be used to produce individual parts that can be assembled into composite components or bonded together using, for example, optically clear adhesives. The adhesive can be selected to provide a specific refractive index. The refractive index of the adhesive can be, for example, between the refractive indices of the directly adjacent portions.

  A typical composite lens material suitable for a lighting device package can have a refractive index of approximately 1.4 or higher, although materials with other refractive indices can also be used.

Encapsulation Material
The encapsulating material fills all or part of the space between the one or more light emitting elements and the compound lens. In accordance with the present invention, the encapsulating material is selected to have a refractive index that is equal to or greater than the refractive index of the innermost lens element of the composite lens, but less than the refractive index of the light emitting element. Typically, the encapsulating material can have a refractive index of approximately 1.55.

  Total internal reflection can be reduced, for example, when no undesirable voids are included at the interface or within the encapsulant. In certain embodiments, the encapsulant material can have a refractive index similar to that of one of the light emitting elements. An encapsulating material having a suitable refractive index slightly lower than the refractive index of the light emitting element can reduce the chance that light undergoes total internal reflection at the optical interface between the light emitting element and the encapsulating material.

  In certain embodiments of the present invention, the encapsulating material may assist in the control of thermally induced stress at or near the optical interface to move the undesirable effects of different coefficients of thermal expansion and varying thermal operating conditions. For example, it can be made of fluid or highly elastic material. The fluid encapsulating material additionally provides thermal diffusion by convection.

  In certain embodiments of the invention, a flexible or fluid encapsulating material or optical silicone can be sealed, for example, between adjacent solid optical components such as a composite lens and other elements such as a substrate. It may be noted that the encapsulating material may or may not be in direct thermal contact with one or more light emitting elements.

  Typical encapsulating materials include, for example, certain silicones and elastomers or gels that contain low ionization impurities such as Cl, K, Na. Multiple encapsulating materials are well known in the art and are available under brand names such as Dow Corning, Nye, or Nusil.

Substrate One or more light emitting elements are operably coupled to the substrate. The substrate can be a ceramic plate, such as AlN, metallized PC substrate, LTCC in metal ceramic, mounting pads for inserting molded leadframe LEDs, and the like known to those skilled in the art. The surface of the substrate facing the cavity, or a specific region thereof, can be, for example, diffusive or specular. Reflective properties can arise, for example, from the application of aluminum or silver coatings and, for example, reflective films.

に従い選択され得る。全内部反射を低減させる屈折率の組み合わせは、非平面及び非並行光学的界面に関する異なる式によって支配され得る。例えば、理想的な平面並行光学的界面に関して、Ａ及びＣの屈折率に基づき媒体Ｂに関して得られる屈折率は、非平面又は非並行界面に関しても媒体Ｂの屈折率に関して合理的な推定を提供し得る。 Refractive Index Evaluation In one embodiment of the invention, the refractive indices n _A , n _B , and n _C of a series of materials A, B, and C allow light to traverse two adjacent planar parallel optical interfaces AB and BC. In order to reduce the possibility of total internal reflection when proceeding,

Can be selected according to The combination of refractive indices that reduce total internal reflection can be governed by different equations for non-planar and non-parallel optical interfaces. For example, for an ideal planar parallel optical interface, the refractive index obtained for medium B based on the refractive indices of A and C provides a reasonable estimate for the refractive index of medium B for non-planar or non-parallel interfaces. obtain.

  Other logical or empirical methods for determining the refractive index of the encapsulating material from the compound lens and the light emitting element based on the refractive index of the surrounding material can be readily understood by those skilled in the art. It can also be appreciated that the refractive index and other parameters of the components of the illuminator package may be selected to optimize one or more optical properties that may include, for example, spectral and spatial radiation distribution.

Coating In some embodiments of the present invention, reflections within the lighting device package can be further reduced by using a thin anti-reflection coating on specific surfaces of specific components of the lighting device package. Such coatings can include multiple layers or films having different optical properties. Each additional coating provides a separate optical interface and can be tuned to improve the optical transmission characteristics at this interface and throughout the lighting device package. Usually, coatings that can suppress unwanted reflections are characterized by a uniform thickness. The thickness is smaller but can be on the order of the wavelength of the light used. Each film can have a suitable refractive index. For example, the outer surface of the composite lens may be coated with a thin layer of material that has a refractive index that is less than the refractive index of the material forming the outermost layer, but higher than the refractive index of the ambient air. Coating materials usually require high permeability, resistance to discoloration, and proper adhesion to the coated component.

  In certain embodiments of the invention, a light emitting element, such as an LED die, has a refractive index between the refractive index of the medium surrounding the film and the refractive index of the light emitting element, eg, an anti-reflective conformal coating. coating) or the like. Similarly, the coating material has particularly good transparency with respect to visible light, resistance to discoloration, and adequate adhesion to the light emitting element.

  The anti-reflective coating can include one or more layers of different materials, or can be microscopically patterned as is well known. Furthermore, many coatings can be designed to provide optimal utilization for light of a particular wavelength or polarization, and for example for a particular angle of incidence. However, it is noted that a properly designed multilayer film can provide high transmission over a wide range of incident angles.

  The invention is described below with reference to specific examples. It will be understood that the following examples are intended to illustrate embodiments of the invention and are not intended to limit the invention in any way.

Example Example 1:
FIG. 1 schematically illustrates a cross-sectional view of an LED package 100 according to one embodiment of the present invention. The LED package has a two-layer lens 110 that defines a cavity 120, which has a hemispherical inner and outer surface and a hemispherical interface between the two layers 132, 134. It will be appreciated that the inner and outer surfaces, as well as the bilayer interface, may have other shapes, and the shapes of the inner and outer surfaces may be different for different embodiments.

  LED dies 190 and 191 are disposed on the substrate 140 and face the cavity. It is noted that a different number of LED dies can be placed inside the package. The cavity 120 can be filled using an encapsulating material. The substrate 140 may be a ceramic plate, such as AlN, FR4, or other printed circuit (PC) substrate, metallized PC substrate, LTCC in metal ceramic, and mounting pads for inserting molded leadframe LEDs. The surface of the substrate 140 facing the cavity, or a specific area of the substrate adjacent to the dies 190 and 191 may be, for example, diffusive or specular. The reflective property can arise from, for example, an aluminum or silver coating.

に従い選択され得る。例えば、レンズ層１３４の屈折率が1.40であり、封入材料１２０の屈折率がおおよそ1.55である場合、レンズ層１３２に関する材料は、おおよそ1.47（＝1.40及び1.55の平方根）を提供するべきである。 The lens 110 includes two layers of material that provide different refractive indices. For example, the outer layer 134 of the lens can be made to have a lower refractive index than the inner layer 132. Inner layer 132 forms an inner hemispherical lens cavity. The lens may have an appropriate wall thickness for the overall size of the package, for example, between approximately 0.2 mm and approximately 1 mm thickness per layer. To assist in obtaining an approximate normal angle of incidence for light impinging on the inner surface of the lens, the inner radius of the hemispherical lens cavity can be approximately three times or more the size of the circular region in which the LED die is placed. The LED die should be positioned so that it is close to the sphere center of the inner hemispherical lens cavity. As described above, the refractive indices n _A , n _B , and n _C of the series of materials A, B, and C are such that the total interior in the case where light travels across two adjacent planar parallel optical interfaces AB and BC. To reduce the possibility of reflection,

Can be selected according to For example, if the refractive index of the lens layer 134 is 1.40 and the refractive index of the encapsulating material 120 is approximately 1.55, the material for the lens layer 132 should provide approximately 1.47 (= 1.40 and the square root of 1.55).

  A two-layer lens can be manufactured in a multi-stage shot forming process. For example, two-step shot formation can be used to process a two-layer compound lens. Two-stage shot formation can be used to manufacture components that provide additional engagement elements. FIG. 1 illustrates an example of a two-layer lens having an engagement element 150. The engagement element may be formed in a mold forming process and provides subsequent mechanical stability by locking the two components relative to each other. The type of engagement can be either destructive or non-destructively releasable joints depending on the shape of the engagement element, the nature of the material used and the nature of the molding process. Generally, shot-formed components increase the geometric complexity of component parts or subcomponents when formed. For example, it may be easier to form the lens layer 132 and then dispose the lens layer 134 in the second formation shot.

Example 2:
FIG. 2 schematically illustrates a cross-sectional view of an LED package 200 according to another embodiment of the present invention. This embodiment is similar to the embodiment illustrated in FIG. 1, but has a compound lens 210 having a solid hemispherical inner lens element 232 covered by an outer lens layer 234. The outer lens layer 234 is attached to the solid hemispherical inner lens element 232 by the engagement element 250.

  In order to house the LED dies 290 and 291 under the compound lens, they are placed in a recess 220 in the substrate 240. The recess defines a cavity between the compound lens 210 and the substrate 240. The surface of the solid hemispherical inner lens element in the vicinity of the LED die is essentially flat, but can be surface processed or structured to improve light penetration from the cavity to the lens element. The cavity can be filled with an encapsulant having an appropriate refractive index.

  In this embodiment, different considerations regarding the refractive index apply compared to the previous embodiment due to the different shape and arrangement of the encapsulant / lens interface. For example, the encapsulating material can have a refractive index of approximately 1.55, and the solid hemispherical inner lens element can have a refractive index of approximately 1.55. Depending on the emission characteristics of the LED die, an inappropriate choice between the solid hemispherical inner lens element of the LED package 200 and the refractive index of the encapsulating material can result in undesirable total internal reflection. The overall light extraction efficiency of the LED package 200 can be improved, for example, when the encapsulating material and the solid hemispheric internal lens element provide equal refractive index.

  In certain embodiments, the formation of a desired radiation pattern, such as, for example, a batwing radiation pattern, can be achieved by placing one or more LED dies adjacent to a suitably formed reflector element (not shown). Can be promoted. For example, the surface of the substrate facing the recess in FIG. 2 or the cavity in FIG. 1 can be coated with a highly reflective material to form a reflector element, or additional reflective elements can be placed in the cavity. . Any of the above components or other additional components that can act as a number of reflector elements can be used in an LED package. The reflector element may be formed outside of a component that is suitably coated or formed, such as, for example, in a metal heat diffuser, in a substrate, or in a lead frame. Alternatively, the reflector element can also be achieved using a material that provides a refractive index that can cause a total internal reflection of a large amount of light.

  Obviously, the above-described embodiments of the present invention can be modified in many ways. Such present or future changes should not be construed as departing from the spirit and scope of the present invention, and all such modifications as will be apparent to those skilled in the art are included within the scope of the appended claims. It is intended to be included in the scope.

FIG. 1 schematically illustrates a cross-sectional view of a lighting device package according to an embodiment of the present invention. FIG. 2 schematically illustrates a cross-sectional view of a lighting device package according to another embodiment of the present invention.

Claims (21)

A lighting device package,
a) one or more light emitting elements operably coupled to the substrate;
b) a compound lens having a surface facing the one or more light emitting elements, the compound lens comprising at least an inner lens element and an outer lens element, the inner lens element having a first refractive index, An external lens element has a second refractive index, the first refractive index is greater than the second refractive index, and defines a cavity in which the compound lens, the one or more light emitting elements and the substrate are closed between them. A compound lens,
c) an encapsulating material filling at least a portion of said cavity, said or equal greater than the first refractive index, have a and encapsulating material having a refractive index lower than the third refractive index of the light emitting element ,
A lighting device package, wherein the inner lens element includes a latching element that engages the outer lens element . A lighting device package,
a) one or more light emitting elements operably coupled to the substrate;
b) a compound lens having a surface facing the one or more light emitting elements, the compound lens comprising at least an inner lens element and an outer lens element, the inner lens element having a first refractive index, An external lens element has a second refractive index, the first refractive index is greater than the second refractive index, and defines a cavity in which the compound lens, the one or more light emitting elements and the substrate are closed between them. A compound lens,
c) an encapsulating material filling at least a portion of the cavity, wherein the encapsulating material has a third refractive index equal to or greater than the first refractive index and smaller than the refractive index of the light emitting element. ,
A lighting device package, wherein the outer lens element includes a latching element that engages the inner lens element. 3. A lighting device package according to claim 1 or claim 2, wherein the encapsulating material is made from a fluid or highly elastic material that can assist in controlling thermally induced stress at or near the optical interface. Lighting device package. 3. A lighting device package according to claim 1 or claim 2 , wherein the substrate has a reflective surface on at least the light emitting element side in proximity to the light emitting element. 5. The lighting device package according to claim 4 , wherein the substrate has a reflective coating disposed at least in proximity to the light emitting element on the light emitting element side. 3. A lighting device package according to claim 1 or claim 2 , wherein the compound lens is at least partially spherical. 3. The lighting device package according to claim 1 or 2 , wherein the compound lens includes a plurality of elements having a refractive index that decreases with increasing distance from the light emitting element. 8. The lighting device package of claim 7 , wherein the plurality of elements have a refractive index that decreases discontinuously. 8. A lighting device package according to claim 7 , wherein the plurality of elements have a continuously decreasing refractive index. The lighting device package according to claim 1 or 2 , wherein the compound lens is manufactured by shot formation. The lighting device package according to claim 1 or 2 , wherein the compound lens is manufactured by multi-stage shot formation. 3. A lighting device package according to claim 1 or 2 , wherein the surface of the inner lens element is coplanar with the side of the substrate having the light emitting element. 3. A lighting device package according to claim 1 or 2 , wherein the surface of the external lens element is coplanar with the side of the substrate having the light emitting elements. 3. A lighting device package according to claim 1 or 2 , wherein the surface of the compound lens element is coplanar with the side of the substrate having the light emitting elements. The lighting device package according to claim 1 or 2 , wherein the light emitting element is disposed in a recess of the substrate. 3. The lighting device package according to claim 1 , wherein an interface between the encapsulating material and the inner lens element is substantially flat, and the third refractive index is set to the first refractive index. Almost equal, lighting device package. 3. The lighting device package according to claim 1 , wherein the third refractive index is larger than the first refractive index. 4. A lighting device package,
a) one or more light emitting elements operably coupled to the substrate;
b) a compound lens arranged to interact with light emitted by the one or more light emitting elements, the compound lens comprising at least an inner lens element and an outer lens element, wherein the inner lens element is The external lens element has a second refractive index, the first refractive index is greater than the second refractive index, and the compound lens, the one or more light emitting elements and the substrate are A compound lens defining a closed cavity in between;
c) an encapsulating material filling at least a portion of said cavity, said or equal greater than the first refractive index, have a and encapsulating material having a refractive index lower than the third refractive index of the light emitting element ,
A lighting device package, wherein the inner lens element includes a latching element that engages the outer lens element . A lighting device package,
a) one or more light emitting elements operably coupled to the substrate;
b) a compound lens arranged to interact with light emitted by the one or more light emitting elements, the compound lens comprising at least an inner lens element and an outer lens element, wherein the inner lens element is The external lens element has a second refractive index, the first refractive index is greater than the second refractive index, and the compound lens, the one or more light emitting elements and the substrate are A compound lens defining a closed cavity in between;
c) an encapsulating material filling at least a portion of the cavity, wherein the encapsulating material has a third refractive index equal to or greater than the first refractive index and smaller than the refractive index of the light emitting element. ,
A lighting device package, wherein the outer lens element includes a latching element that engages the inner lens element. 20. A lighting device package according to claim 18 or claim 19 , wherein the compound lens has a surface facing the one or more light emitting elements, thereby being emitted by the compound lens and the light emitting element. A lighting device package that provides direct interaction between the light. 21. A lighting device package according to claim 20 , wherein the compound lens is arranged to interact indirectly with light emitted by the light emitting element via one or more optical elements. Equipment package.

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