Patent Application
20150236221
The present invention relates to the emission methods of light emitting diodes and how intrinsic recombination semiconductor photons (i.e. 450 nanometre) eminent with wide band gap semiconductors designed for use as light emitting diodes, are converted by quantum secondary emission of high efficiency phosphors, to a usable range of white light. One of the problems with conventional phosphor methods is with gradual white colour temperature degradation due to ambient thermal fluctuations.
Within the next five years, it is likely that white light emitting diodes (WLEDs) will be used for all interior and external lighting functions, from homes, industry and even vehicles. Because of such wide scale potential use, WLEDs have attracted both scientific attention and commercial interest. Different approaches for white light generation such as multi-chip WLEDs, monolithic WLEDs and colour-conversion WLEDs have been extensively investigated. Among these, multi-chip white LEDs (and monolithic WLEDs, in principle, for the same matter) tend to exhibit higher electrical-to-light conversion efficiencies when compared with colour-conversion WLEDs, for the multi-chip WLEDs do not have additional energy losses caused by the Stokes shift and non-radiative recombination, unlike in the phosphor coating of colour-conversion WLEDs. Additionally, multi-chip WLEDs do not suffer ageing problems related to the phosphor, which affects the lifetime of colour-conversion WLEDs. However, for multi-chip WLEDs, the driving electric circuit is typically comparatively complex for general illumination purposes, leading to increased costs. As a result, the colour-conversion approach provides an advantage specifically in having simple circuits (and thus reduced cost) when compared to the multi-chip WLED approach.
Today, using the colour-conversion technique, phosphor based WLEDs have been widely commercialized and are currently in use. In phosphor-based colour conversion, however, difficulties in controlling granule size systematically, and mixing and depositing films uniformly pose the most fundamental disadvantages, which result in undesired visible colour variations.
As an alternative approach, quantum dots have recently been used for colour conversion in white light generation.
The novelty of the present invention teaches that there are other method means of producing white light utilizing quantum dots and/or high efficiency phosphors, in combination with micro/nano spheres and nano-particles of metal, silicon or similar semiconductor material from the IIIB and IVB Group of the Periodic Table in a photon transparent colloidal stationary suspension media means. The present invention also teaches that white-light LED devices based on single size, ultra-small cadmium selenide (CdSe) quantum dots that possess broadband emission (420-710 nm). When encapsulated in a polymer and coated on commercial UV LEDs, these quantum dots act as frequency down converters to produce high quality white light. These devices emit very pure white light with excellent CIE coordinates (0.35, 0.31) and a very high color rendering index of 93 when excited with a 365 nm LED.
What is utilized is a plurality of components in a GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER to increase the extraction efficiency and decrease UV light leakage from the device. This increases extraction efficiency by reflecting emitted white light out of the device that would normally be lost. Second, the tradeoff of color quality and efficiency that results from using blue LEDs for excitation: unabsorbed blue light will imbalance the white-light spectrum, but the conversion of blue to white light yields a lower Stokes loss than UV excitation light.
The evolution of wide band gap semiconductors such as InGaAs and InGaN for utilization in high brightness white or single colour light emitting diodes has advanced with prior art focusing in areas of improved yield rate (binning), improvements in thermal removal appliques, and colour range stabilization; not to mention thermal effects on colour shift and light output efficiency. The focus on colour output by utilizing high photon output phosphors remains the industry standard for low forward current LED dies (3×10̂2 Amperes) and high forward current LED dies (2.5×10̂1 Amperes and greater). Current drawbacks are with thermal fluctuations over time with high efficiency phosphors and brightness output efficiency. Little or no attention, as indicated from the lack of prior art, has been paid to concept of optical lens systems being a more important issue than just placing a small quantity of phosphor over the LED die and covering it over with a small amount of transparent epoxy or polymer plastic. The present invention teaches that careful analysis of the action of photon conversion from the intrinsic 450 (average) nanometre photons propagating from the LED die-to-phosphor atoms are a result of Raman Scattering. Raman Scattering is inelastic and therefore total kinetic energy is not conserved, which results in the scattered photons not possessing the same frequency and wavelength as the incident photons from the a LED die. The conclusion is simply that the light output, as a result of this simple quantum mechanical process, is the combination of the secondary Raman scattered photons and the incident 450 nanometre photons from the LED die. This is the methodology means of producing white light, and the colour temperature range of this white light varies as to the chemical composition of the phosphor utilized. That remains the conclusion for the interest and investigation of the LED industry currently. There has been to date, across the board focus on increasing the lumens per watt by either refinement of the LED die selection by binning or by incorporating a plurality of LED dies in various cascoding, or cascading, or combinations of both. The present invention teaches that instead of Raman Scattering solely being responsible for the light output of fabricated LEDs currently; a novel combination approach utilizing Rayleigh Scattering, Mie Scattering, Stokes Scattering, quantum dots, nano-particles of metal, silicon or similar semiconductor material from the IIIB and IVB Group of the Periodic Table and micro or nano transparent spheres of glass or polymer plastic. This novel approach takes advantage of utilizing incident photons emitted from an LED die to excite said quantum dots that are tuned to a specific narrow pass-band; by definition quantum dots are semiconductors whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. Quantum dot electronic characteristics are closely related to the size and shape of the individual crystal. Generally, the smaller the size of the crystal, the larger the band gap, the greater the difference in exiton energy between the highest valence band and the lowest conduction band becomes, therefore more energy is needed to excite the dot, and concurrently, more energy is released when the crystal returns to its resting state. For example, in fluorescent dye applications, this equates to higher frequencies of light emitted after excitation of the dot as the crystal size grows smaller, resulting in a color shift from red to blue in the light emitted. In addition to such tuning, a main advantage with quantum dots is that, because of the high level of control possible over the size of the crystals produced, it is possible to have very precise control over the conductive properties of the material. Quantum dots of different sizes can be assembled into a gradient multi-layer nano-film. Typical sizes of quantum dots range from 2 to 10 nm (1-50 atoms) in diameter, and by band gap engineering techniques can be finely tuned to a wide spectrum of individual narrow band gap Gaussian distribution curves for optimized photon output. With quantum dots in the range of 2 to 10 nm the highly tuned colour range of monochromatic photon release is well defined and stable with temperature variations and are much more efficient that phosphors by at least 30% increase, but an unusual phenomena occurs when the quantum dot becomes less than 1.7 nm in diameter.
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections that undergo scattering are often called diffuse reflections and unscattered reflections are called specular (mirror-like) reflections
The types of non-uniformities that cause scattering, sometimes known as scatterers or scattering centers, are too numerous to list, but a small sample includes particles, bubbles, droplets, density fluctuations in fluids, crystallites in polycrystalline solids, defects in monocrystalline solids, surface roughness, cells in organisms, and textile fibers in clothing. The effects of such features on the path of almost any type of propagating wave or moving particle can be described in the framework of scattering theory.
Dominant areas where scattering and scattering theory are significant include radar sensing, medical ultrasound, semiconductor wafer inspection, polymerization process monitoring, acoustic tiling, free-space communications, and computer-generated imagery.
The types of scattering utilized with the present invention are Rayleigh Scattering, Mie Scattering, and Stokes Scattering.
Rayleigh Scattering is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. The particles may be individual atoms or molecules. It can occur when light travels through transparent solids and liquids. Rayleigh scattering is a function of the electric polarizability of the particles.
Rayleigh scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the blue color of the sky and the yellow tone of the sun itself.
Scattering by particles similar to or larger than the wavelength of light is typically treated by the Mie theory, the discrete dipole approximation and other computational techniques. Rayleigh scattering applies to particles that are small with respect to wavelengths of light, and that are optically “soft” (i.e. with a refractive index close to 1). On the other hand, Anomalous Diffraction Theory applies to optically soft but larger particles.
The size of a scattering particle is parameterized by the ratio x (eq. 1) of its characteristic dimension r and wavelength λ:
Rayleigh scattering can be defined as scattering in the small size parameter regime x<<1. Scattering from larger spherical particles is explained by the Mie theory for an arbitrary size parameter x. For small x the Mie theory reduces to the Rayleigh approximation.
The amount of Rayleigh scattering that occurs for a beam of light depends upon the size of the particles and the wavelength of the light. Specifically, the intensity of the scattered light varies as the sixth power of the particle size, and varies inversely with the fourth power of the wavelength.
The intensity/of light scattered by a single small particle from a beam of unpolarized light of wavelength A and intensity I0 is given by (eq. 2):
where R is the distance to the particle, θ is the scattering angle, n is the refractive index of the particle, and d is the diameter of the particle.
The Rayleigh scattering coefficient (eq. 3) for a group of scattering particles is the number of particles per unit volume N times the cross-section. As with all wave effects, for incoherent scattering the scattered powers add arithmetically, while for coherent scattering, such as if the particles are very near each other, the fields add arithmetically and the sum must be squared to obtain the total scattered power.
Rayleigh scattering also occurs from individual molecules. Here the scattering is due to the molecular polarizability α, which describes how much the electrical charges on the molecule will move in an electric field. In this case, the Rayleigh scattering intensity for a single particle is given by (eq. 4)
The amount of Rayleigh scattering from a single particle can also be expressed as a cross section a. For example, the major constituent of the atmosphere, nitrogen, has a Rayleigh cross section of 5.1×10-31 m2 at a wavelength of 532 nm (green light). This means that at atmospheric pressure, about a fraction 10−5 of light will be scattered for every meter of travel.
The strong wavelength dependence of the scattering (˜λ−4) means that shorter (blue) wavelengths are scattered more strongly than longer (red) wavelengths. This results in the indirect blue light coming from all regions of the sky. Rayleigh scattering is a good approximation of the manner in which light scattering occurs within various media for which scattering particles have a small size parameter.
Shorter wavelengths are scattered more intensely than longer wavelengths. This means that blue light has a higher probability of being scattered than red light.
This is the reason the sky appears to be blue. Sunlight, which is made up of a continuous spectrum of wavelengths, scatters from atmospheric particles. Since the particle size is much smaller than the wavelengths of light, the shorter wavelength blue light is scattered more intensely.
A portion of the light coming from the sun scatters off molecules and other small particles in the atmosphere. It is this scattered light that gives the sky its brightness and its color. As previously explained, Rayleigh scattering is inversely proportional to the fourth power of wavelength, so that shorter wavelength violet and blue light will scatter more than the longer wavelengths (yellow and especially red light). The resulting color, which appears like a pale blue, actually is a mixture of all the scattered colors, mainly blue and green. Violet, though strongly scattered, is a minor component of the solar spectrum and is less efficiently detected by the human eye. Conversely, glancing toward the sun, the colors that were not scattered away—the longer wavelengths such as red and yellow light—are directly visible, giving the sun itself a slightly yellowish hue. Viewed from outer space, however, the sky is black and the sun is white.
The reddening of sunlight is intensified when the sun is near the horizon, because the volume of air through which sunlight must pass is significantly greater than when the sun is high in the sky. The Rayleigh scattering effect is therefore increased, removing virtually all blue light from the direct path to the observer. The remaining unscattered light is mostly of a longer wavelength, and therefore appears to be orange.
The scattering of light from larger particles is known as Mie Scattering; the Mie solution to Maxwell's equations (also known as the Lorenz-Mie solution, the Lorenz-Mie-Debye solution or Mie scattering) describes the scattering of electromagnetic radiation by a sphere. The solution takes the form of an analytical infinite series. The larger particles scatter the light in the forward direction. The larger a particle, the more intense the light scattered in the forward direction. Mie Scattering is not strongly wavelength dependent. It also produces a white glare around the particle. This is the reason fog or mist appears to be white and why the sky appears to be white near the horizon during a clear day.
Rayleigh scattering is strongly dependent upon the size of the particle and the wavelengths. The intensity of the Rayleigh scattered radiation increases rapidly as the ratio of particle size to wavelength increases. Furthermore, the intensity of Rayleigh scattered radiation is identical in the forward and reverse directions.
The Rayleigh scattering model breaks down when the particle size becomes larger than around 10% of the wavelength of the incident radiation. In the case of particles with dimensions greater than this, Mie's scattering model can be used to find the intensity of the scattered radiation. The intensity of Mie scattered radiation is given by the summation of an infinite series of terms rather than by a simple mathematical expression. It can be shown, however, that Mie scattering differs from Rayleigh scattering in several respects; it is roughly independent of wavelength and it is larger in the forward direction than in the reverse direction. The greater the particle size, the more of the light is scattered in the forward direction.
This present invention and novel improvement over prior art, relates to a plurality of novel embodiments for creating white light output or single colour light output with light emitting diodes by utilizing a novel permanent or removable GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER system means for efficient and enhanced photon conversion, disposed and in communication with a light emitting diode system means.
It is the intention of the present invention to teach through said plurality of novel embodiments that improves white light output efficiency or single colour light output efficiency in light emitting diodes, which are thermally stabilized and exist with a narrow pass-band of photon emission from quantum dots compared to conventional phosphors; resulting from utilizing the embodiments.
Another intention of the present invention is to utilize “heavy metal free” quantum dots, but not limited to “heavy metal free” quantum dots as a component of a plurality of components in a GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER.
It is another intention of the invention to utilize nano-particles of metal, silicon or similar semiconductor material from the IIIB and IVB Group of the Periodic Table, but not limited to said nano-particles of silicon or similar semiconductor material from the IIIB and IVB Group of the Periodic Table as a component that by Rayleigh Scattering, acts as a mirror or reflective optical antenna to scatter photons within the volume of the GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER.
It is another intention of the invention to utilize micro or nano transparent spheres of glass or polymer plastic a component that by Mie Scattering, acts as a mirror or reflective optical antenna to scatter photons within the volume of the GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER.
Another intention of the invention is for utilize a Gaussian curvilinear surface volume comprised of a photon transparent epoxy or polymer plastic embodiment that contains and is in communication with the quantum dots, nano-particles, and micro or nano spheres.
It is also the intention the present invention to have the photon transparent epoxy or polymer plastic embodiment mounted over the effective light emitted region of the light emitting diode assembly so that any and all incident photons released as a result of forward biasing the light emitting diode assembly, will travel throughout said photon transparent epoxy or polymer plastic embodiment for quantum interaction with the quantum dots, nano-particles, and nano/micro spheres to establish a designed white colour temperature expressed in degrees Kelvin or with a designed single colour temperature expressed in degrees Kelvin.
Further, another intention of the present invention is to utilize a plurality of varying sizes of quantum dots in order to create a white light emitting diode removable lens system means; and to utilize a plurality of single narrow band quantum dots to create a monochromatic light emitting diode removable lens system means.
Another novel intention of the present embodiment of said present invention is for the creation of a “white light” removable lens system means that utilizes a plurality of ultra small quantum dots of atomic diameters less than 2 nanometres; and by their broadband emission (420-710 nm) throughout most of the visible light spectrum, while not suffering from self absorption, produce “white light” from a single size group of the ultra small quantum dots less than 2 nanometres in atomic diameter.
Further it is another intention of the present invention to utilize the GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER as a removable lens system method means to make available a plurality of changeable lens options during or after production of LEDs for purposes of changing the colour output of any light emitting diode simply by inserting a changeable and easily removable surface lens means.
With reference to
Another embodiment of said present invention, and relating to
A specific quantum dot arrangement of at least one or a plurality combination arrangement for a specific desired colour that is formed into the GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER, as illustrated in
In accord with quantum mechanics, each silicon mirror 104 will resonate when excited by soft UV (˜450 nm) light to establish a standing wave emanating within. The precise wave pattern is determined by the wavelength that the incident light has in silicon, which is about one-third of its value in air. Each silicon mirror 104 essentially behaves like an antenna, absorbing light and re-emitting it in a form possessing the symmetry of the standing wave inside the flat silicon nano-structures 104, with said light from said silicon mirrors 104 interfering constructively or destructively, depending on the direction of the incident light.
Said silicon mirrors 104 resonate like an electric dipole when excited by soft uV light at ˜450 nm. As said silicon mirrors 104 are arranged in a pseudo-random arrangement, emissions from each dipole 104 interfere constructively when light of this wavelength is used and a single beam of light emerges from the same side of the normal as the incoming beam in what is known as negative transmission.
When 450 nm light hits the silicon mirrors 104, an isotropic standing wave is formed and radiation exits in four orthogonal directions. This in effect increases the amount of photon emission propagated from the quantum dots contained within the said GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER 102 as illustrated in
As shown in
In one embodiment of said present invention as shown in
Another embodiment of the present invention is illustrated in
It should be obvious and understood by those steeped in the art that any embodiment of the present invention is not limited by utilizing a plurality combination of more than one type size of quantum dot; and whereby the size of a quantum dot determines its characteristic monochromatic spectra emission due to incident photon absorption emanating from the intrinsic photon emission of a wide band gap semiconductor fabricated as a light emitting diode. The plurality of a combination of more than one type size of quantum dot is utilized to produce “white” light emitted and propagated from a fabricated light emitting diode, and any selection of a desired “white” colour temperature range given in degrees Kelvin is controlled by careful ratio selection of a plurality of red to green quantum dots. Thus it is established by some prior art that a stand-alone chemical colloidal suspension combination of different size diameter quantum dots, in the range of 2 to 10 nanometres, can produce multi-chromatic colour resultants or that by utilizing a combination of red, green and blue quantum dots a “white” colour will result.
However, another approach and intention of the present invention is to utilize ultra-small quantum dots 123 (shown in
Michael A. Schreuder (Dept. of Chemistry at Vanderbilt University) and Sandra J. Rosenthal (Department of Electrical Engineering and Computer Science and Chemistry Dept. at Vanderbilt University) report in a 2010 article titled: “White Light-Emitting Diodes Based on Ultra-small CdSe Nano-crystal Electroluminescence”[1] that white light-emitting diodes fabricated with ultra-small CdSe nanocrystals, which demonstrate electroluminescence from a size of nanocrystals (<2 nm) previously thought to be unattainable. These LEDs have excellent color characteristics, defined by their pure white CIE color coordinates (0.333, 0.333), correlated colour temperatures of 5461-6007 K, and color rendering indexes as high as 96.6. The effect of high voltage on the trap states responsible for the white emission is also described.
The illustration and graph of
Another embodiment of the present invention is in the utilization of a disposed layered combination of a stationary colloidal suspension volume 500 as shown in
The first disposed strip of a red photon transparent stationary colloidal epoxy suspension volume segment 502R contains said plurality of red quantum dots, the nano-particles and said glass or polymer micro spheres; the second disposed strip blue photon transparent stationary colloidal epoxy suspension volume segment 504B contains the plurality of blue quantum dots, the nano-particles and said glass or polymer micro spheres; and a third disposed strip green photon transparent stationary colloidal epoxy suspension volume segment 503G contains the plurality of green quantum dots, said nano-particles and the glass or polymer micro spheres. Disposed and in electrical and mechanical communication with the each individual red strip member means 502R, blue strip segment 504B, and green strip 503G are three disposed individual and electrically separate electrically conductive metallic connexions to the outside world; one said connexion for said red strip 502RC, one said connexion for said blue strip 504BC, and one connexion for said green strip 503GC. Also disposed and in common electrical connexion with all said red 502R, blue 504B, and green 503G strip segments is electrically conductive metallic strip (ground) member means 501Gnd that is the electrical common ground connexion to the outside world.
In this embodiment of the present invention shown in
Another novel embodiment according to the invention is shown in
In addition, this preferred embodiment of the invention utilizes a microcontroller that is in communication with an enable and intensity level circuit 704, and microcontroller sends a command signal on an enable/disable line 704EL to a logic control circuit 704En that is in communication with a buffer output stage 704B and whereby buffer output stage 704B is in communication with blue quantum dot strip 504B by blue signal line 704BL. Further, said microcontroller 701 controls on/off enabling and intensity colour levels by sending a programmed enable/disable logic decision signal on its control line 704EL and sends an intensity level command by a control line 704CL to a intensity level circuit (like a digital to analogue converter) 704Int and this signal level is isolated by buffer stage 704B and sent along blue signal line 704BL and is in communication with blue quantum dot strip 504B; to control the on and off and colour intensity of said blue quantum dot strip 504 as determined by an algorithm.
In addition, this preferred embodiment of the invention utilizes a microcontroller that is in communication with an enable and intensity level circuit 703, and microcontroller sends a command signal on an enable/disable line 703EL to a logic control circuit 703En that is in communication with a buffer output stage 703B and whereby buffer output stage 703B is in communication with green quantum dot strip 503R by green signal line 703RL. Further, said microcontroller 701 controls on/off enabling and intensity colour levels by sending a programmed enable/disable logic decision signal on its control line 703EL and sends an intensity level command by a control line 703CL to a intensity level circuit (like a digital to analogue converter) 703Int and this signal level is isolated by buffer stage 703B and sent along green signal line 703RL and is in communication with green quantum dot strip 503R; to control the on and off and colour intensity of said green quantum dot strip 503 as determined by an algorithm.
Thus from having said microcontroller 701 given instructions from an algorithm, and with a LED that contains ultra-small quantum dots 123 (as shown in
Another preferred embodiment of the invention is illustrated by an exploded view in
A red quantum dot strip 502R is disposed on uV filter film 501uV and is in electrical communication with a red conductive electrically isolated control channel 502RC; a blue quantum dot strip 504B is disposed on uV filter film 501uV and is in electrical communication with a blue conductive electrically isolated control channel 504BC; a green quantum dot strip 503G is disposed on uV filter film 501uV and is in electrical communication with a green conductive electrically isolated control channel 503GC.
Another embodiment of said present invention is illustrated by two views in
In
Another preferred embodiment of the present invention is shown in the electrical diagram 800 of
Another embodiment of said present invention is for such action of said circuit component 200R to exist with several optional methods or apparatus of utilizing a current limit method or apparatus, but not limited to current limiting alone; and it can exist with such action utilizing the voltage enabling, but not limited to only voltage enabling means; and it can exist with such action utilizing intensity colour control, but not limited to only intensity colour control. Any or all feature of current limiting, voltage enabling and intensity colour control can exist by selective design features of a preprogrammed algorithm or by a specific fabrication design feature selection. Each said dual channel cascaded LED array system means 900 that is disposed with two COB LED array 200 on a common heat sink base substrate can be electrically connected to operate in parallel from a 120 VAC power mains source such as exists in the US and Japan or connected in series to operate from a 240 VAC power mains source such as exists in the UK and EU; and the parallel or series combination selection can be connected in either design as selected internally during fabrication or can be connected externally by a consumer.
An embodiment is an implementation or example of said invention. References in the specification to “an embodiment,” “another embodiment,” “one embodiment,” “some embodiments,” or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments of the present invention. The various appearances of “an embodiment,” “one embodiment,” or “some embodiments” are not necessarily all referring to the same embodiments.
If the specification states a component, feature, structure, or characteristic “may,” “might,” “can,” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included. If the specification or claim refers to “a” or “an” element, that does not mean there is only one of the element. If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional element.
The present invention is not restricted to the particular details described herein. Indeed, many other variations of the foregoing description and drawings may be made within the scope of said present invention. Accordingly, it is the following claims including any amendments thereto that define the scope of the present invention.
The present invention is a Divisional application by the same inventor of patent application entitled A GAUSSIAN SURFACE LENS QUANTUM PHOTON CONVERTER AND METHODS OF CONTROLLING LED COLOUR AND INTENSITY, filed 7 May 2012, Ser. No. 13/465,604.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13465406 | May 2012 | US |
| Child | 14657149 | US |
