High Luminous Flux Research Articles

Roll-to-roll printed and assembled large area LED lighting element

Novel continuous and mass customizable light-emitting diode (LED) lighting foil system, capable to produce adequate lighting levels for general lighting, was designed, processed, and characterized. Lighting element substrate was processed by roll-to-roll (R2R) printing using silver ink and automatic bonding of LEDs and current regulators on polyethylene terephthalate (PET) substrate using isotropic conductive adhesive (ICA). Demonstrator consisting of two basic lighting elements contained 98 LEDs and produced 860 lm when running with 25 mA operational current through the LEDs when using total electrical driving power of 8.4 W. Measured power conversion efficiency of the demonstrator was 31 % and efficacy 102 lm/W. Element produced 460 lx illumination level measured by an illumination level meter at element’s central axis at distance of 1 m. At a distance of 2 m, illumination level was 110 lx, respectively. Temperature measurements with T3Ster thermal characterization instrument showed that when driving LED with maximum nominal driving current of 100 mA, LED junction temperature was about 120 °C, when lighting element was in air in room temperature. Accelerated environmental stress tests consisting of 500 cycles from −40 … +80 °C in aging oven and 1000 h in +60 °C/95 % RH climate chamber were performed to test samples without any failures. In addition, over 700 bending cycles using 20 mm bending radius were performed to test samples without any failures, so bonding of LEDs were shown reliable according to these tests. Achieved results proved that thin, flexible, and large area high luminous flux lighting elements and systems can be processed based on plastic foil manufactured using R2R silver ink printing and R2R automatic bonding of LEDs and regulator components using ICA on that foil.

Saving Phosphor by 150% and Producing High Color-Rendering Index Candlelight LEDs Containing Composite Photonic Crystals

A technique that saved phosphor use by 150% was applied to warm white light-emitting diodes containing composite colloidal photonic crystals (c-CPhCs) to develop an electrical source of candlelight that exhibits a high luminous flux (52 lm) and a high color-rendering index (CRI; 94). This physiologically friendly light source, which was designed to mimic the color temperature of candlelight, provides at least eight-times more luminous flux than traditional candles do. Furthermore, a UV-based adhesive curing method for enhancing the adhesion properties of c-CPhCs was also developed. A novel, inexpensive technology was implemented to produce high-CRI candlelight LEDs for use as a residential light source.

Silicone hybrid materials useful for the encapsulation of light-emitting diodes

Novel ZrO2/silicone hybrid materials useful for the encapsulation of light-emitting diodes (LEDs) are synthesized by in situ sol–gel reaction of zirconium propoxide directly in a commercial-grade silicone resin. The domain size of the produced ZrO2 particles in the hybrid materials is controlled to be smaller than 350 nm based on SEM pictures to have a high optical transparency greater than 95% at 400 nm. The refractive index of the hybrid material increases from 1.52 to 1.62 when its ZrO2 content is increased from 1 to 15 wt.%. In addition, these hybrid materials are stable enough to tolerate the treatment of soldering at 260 °C for 2 min. For the hybrid materials with the ZrO2 content up to 7 wt.%, their weight-loss values are less than 0.25%. Finally, these hybrid materials are applied to encapsulate LEDs and their luminous flux is measured. The results showed that all the hybrid materials have higher luminous flux than the pristine silicone material. The luminous flux increased to a plateau value of 4.35 lm as the ZrO2 content in the hybrid material was increased to 3.0 wt.%. For all the hybrid materials studied here, the ZrO2/AB3 hybrid is considered to be the most suitable candidate as the encapsulating material for the LED used in this study.

Benefits of glass fibers in solar fiber optic lighting systems

The transmission properties and coupling of solar light have been studied for glass core multimode fibers in order to verify their benefits for a solar fiber optic lighting system. The light transportation distance can be extended from 20 m with plastic fibers to over 100 m with the kind of glass fibers studied here. A high luminous flux, full visible spectrum, as well as an outstanding color rendering index (98) and correlated color temperature similar to the direct sun light outside have been obtained. Thus the outstanding quality of solar light transmitted through these fibers would improve the visibility of all kinds of objects compared to fluorescent and other artificial lighting. Annual relative lighting energy savings of 36% in Uppsala, Sweden, and 76% in Dubai were estimated in an office environment. The absolute savings can be doubled by using glass optical fibers, and are estimated to be in the order of 550 kWh/year in Sweden and 1160 kWh/year in Dubai for one system of only 0.159 m(2) total light collecting area. The savings are dependent on the fiber length, the daily usage time of the interior, the type of artificial lighting substituted, the system light output flux, and the available time of sunny weather at the geographic location.

Illumination performance and energy saving of a solar fiber optic lighting system

The illumination performance and energy savings of a solar fiber optic lighting system have been verified in a study hall--corridor interior. The system provides intensive white light with a high luminous flux of 4500 lm under 130000 lx direct sun radiation at a 10 m fiber distance from the sun-tracking light collector. The color temperature that describes the light color perceived is 5800 ± 300 K, i.e. close to the direct sunlight outside, and the color rendering index (86), that describes how well colors are rendered under the light source, is higher for the solar lights than for the supplementary fluorescent lights (77). Thus this high quality solar lighting improves the visibility of all kinds of objects compared to the fluorescent lights. Annual lighting energy savings of 19% in Uppsala, Sweden and 46% in southern Europe were estimated for a study hall interior, as well as 27% and 55% respectively in an interior illuminated 16 h per day all days of a year.

Ceramic Phosphors for Light Conversion in LEDs

In the present article we briefly review some materials research aspects related to ceramic phosphors and discuss both typical characteristics as well as unique features of such optical converters. Devices with more efficiency and/or higher luminous flux that are based on converting the pump light crucially enable the use of LEDs in white and single color illumination schemes for many applications. Advantages of generating white light with ceramics versus powder-in-silicone are discussed. High performance of single color conversion LEDs in terms of efficacy and external quantum efficiency for the visible region boost the output in data or home cinema projection and automotive signaling but more applications are appearing.

Layer Encapsulation of Quantum Dots on Chip on Board Type White LEDs

The chip on board (COB) types LED modules were fabricated by using metal core printed circuit board (mcPCB), aluminium oxide (Al2O3) and aluminium nitride (AlN) as submounts of LED chips. The radiant flux of the LEDs exhibited slight difference in terms of the LED chip bonding process in which eutectic bonding gave higher radiant flux than Ag epoxy bonding in both AlN and Al2O3 substrates. However the LED modules fabricated on AlN ceramic substrate exhibited higher radiant flux than the one on Al2O3 substrate at high current due to more effective heat dissipation in case of AlN substrate. The WLED modules encapsulated with YAG phosphor and red QD by layer-by-layer mode showed both high total luminous flux and high color rendering index.

Gender-related differences in physiologic color space: a functional transcranial Doppler (f TCD) study

Simultaneous color contrast and color constancy are memory processes associated with color vision, however, the gender-related differences of 'physiologic color space' remains unknown. Color processing was studied in 16 (8 men and 8 women) right-handed healthy subjects using functional transcranial Doppler (fTCD) technique. Mean flow velocity (MFV) was recorded in both right (RMCA) and left (LMCA) middle cerebral arteries in dark and white light conditions, and during color (blue and yellow) stimulations. The data was plotted in a 3D quadratic curve fit to derive a 'physiologic color space' showing the effects of luminance and chromatic contrasts. In men, wavelength-differencing of opponent pairs (yellow-blue) was adjudged by changes in the RMCA MFV for Yellow plotted on the Y-axis, and the RMCA MFV for Blue plotted on the X-axis. In women, frequency-differencing for opponent pairs (blue-yellow) was adjudged by changes in the LMCA MFV for Yellow plotted on the Y-axis, and the LMCA MFV for Blue plotted on the X-axis. The luminance effect on the LMCA MFV in response to white light with the highest luminous flux, was plotted on the (Z - axis), in both men and women. The 3D-color space for women was a mirror-image of that for men, and showed enhanced color constancy. The exponential function model was applied to the data in men, while the logarithmic function model was applied to the data in women. Color space determination may be useful in the study of color memory, adaptive neuroplasticity, cognitive impairment in stroke and neurodegenerative diseases.

Performance of High-luminous Efficacy White LEDs

The performance of InGaN/YAG white LEDs for lighting applications is reviewed. Advanced small-chip-technology has achieved high-luminous efficacy white LED of almost 200lm/W by improving internal efficiency, extraction efficiency and electrical resistance. In addition, high-luminous flux device of 10,000lm by flip-chip array has been also developed by large-chip-technology.

Review on Development and Application of Interference Imaging Spectrometry

Interference imaging spectrometry is in the frontier and hotspot of remote sensing technology and application.It has enormous application potential for its characteristics such as high luminous flux,high spectral resolution,and high-stability of imaging.We introduce the basic principles of interference imaging spectrometer.We will also give an overview of data processing technologies including spectrum reconstruction,calibration and atmospheric correction.Some representative spectrometers and their applications are reviewed in brief.Finally,it is pointed out that the effective approach to promote the development of interference imaging spectrometry shall be carrying out some research and applications based on HSI instrument loaded on HJ-1A satellite in our country.

White light emitting diodes with super-high luminous efficacy

We fabricated three types of high luminous efficacy white light emitting diodes (LEDs). The first was a white LED with a high luminous efficacy (ηL) of 249 lm W−1 and a high luminous flux (ϕv) of 14.4 lm at a forward-bias current of 20 mA. This ηL was approximately triple that of a tri-phosphor fluorescent lamp (90 lm W−1). The blue LED used as the excitation source in this white LED had a high output power (ϕe) of 47.1 mW and a high external quantum efficiency (ηex) of 84.3%. The second was a high-power white LED, fabricated from the above high-power blue LED, and had a high ϕe of 756 mW at 350 mA. ϕv and ηL of the high-power white LED were 203 lm and 183 lm W−1 at 350 mA, respectively. The third was a high-power white LED fabricated from four high-power blue LED dies. ϕv and ηL of the high-power white LED were 1913 lm and 135 lm W−1 at 1 A, respectively. The white LED had a higher flux than a 20 W-class fluorescent lamp and 1.5 times the luminous efficacy of a tri-phosphor fluorescent lamp (90 lm W−1).

25.4: High‐Brightness Large‐Area White OLED Fabricated by Meniscus Printing Process

AbstractWe demonstrated high‐brightness large‐area, white organic light‐emitting diode (OLED) consisting of printing‐processed organic semiconductor layers. Meniscus printing process was applied to the substrate with 2 μm‐high stripe‐shape auxiliary electrodes. The OLED panel showed white emission all over the whole emitting area of 58 mm × 52 mm, high average luminance of 10,000 cd/m2, luminance uniformity of 40 %, and high luminous flux of 95 lm.

Superior Illuminant Characteristics of Color Rendering and Luminous Efficacy in Multilayered Phosphor Conversion White Light Sources Excited by Near-Ultraviolet Light-Emitting Diodes

We have demonstrated that a phosphor conversion (PC) white light-emitting diode (LED) light source composed of multi-layered (ML) red, green, and blue (RGB) phosphors with a near-ultraviolet (n-UV) LED as an excitation source shows excellent color rendering, luminous efficacy, and luminous flux. The ML-phosphor structure consists of vertically stacked layers and could significantly reduce cascade excitation loss compared with a mixed RGB PC white LED. A high luminous efficacy of 82 lm/W with a high color-rendering index (CRI) of over 90 was achieved using a ML-RGB PC white LED. The ML-RGB structure also enables a white LED with an ultrahigh CRI of 99 and a high luminous efficacy comparable to that of a high CRI fluorescent lamp. We have also fabricated a high-power ML-PC white LED excited by an n-UV LED. In one package, a high luminous flux of 61 lm at a high CRI of 94 was obtained.

Analysis on the high luminous flux white light from GaN-based laser diode

We fabricated a phosphor-conversion white light using an InGaN laser diode that emits 445 nm and phosphor that emits in the yellow region when excited by the blue laser light. At 500 mA injection current the luminous flux and the luminous efficacy were 113 lm and 44 lm/W, respectively. The relationship of the luminous flux and the luminous efficacy of the white light with an injection current were discussed. Based on the evaluation method for luminous efficacy of light sources established by the Commission International de I’Eclairage (CIE) and the phosphor used in this experiment, a theoretical analysis of the experiment results and the maximum luminous efficacy of this white light fabrication method were also presented.

Successful fabrication of white light emitting diodes by using extremely high external quantum efficiency blue chips

AbstractWe fabricated three types of high luminous efficiency white light emitting diodes (LEDs). The first is the white LED, which had a high luminous efficiency (ηL) of 161 lm/W with the high luminous flux (ϕv) of 9.89 lm at a forwardbias current of 20 mA. The blue LED had a high power (ϕe) of 42.2 mW and high external quantum efficiency (ηex) of 75.5%. The second is the high luminous efficiency white LED with a low voltage (Vf) of 2.80 V, which was almost equal to the theoretical limit. ηL and wall‐plug efficiency (WPE) is 169 lm/W and 50.8%, respectively, at 20 mA. They are approximately twice higher than those of a tri‐phosphor fluorescent lamp (90 lm/W and 25%). The third is the high power white LED fabricated from the high power blue LED with high ϕe of 651 mW at 350 mA. ϕv, ηL and WPE of the high power white LED are 145 lm, 134 lm/W and 39.6% at 350 mA, respectively. Moreover, at 1 A, ϕv and ηL were 361 lm and 97 lm/W, respectively. Thus ϕv is equivalent to that of a 30 W‐class incandescent lamp. And, ηL is slightly higher than that of a tri‐phosphor fluorescent lamp. Moreover, we fabricated the high power near ultra‐violet, bluish‐green and green LEDs, whose ϕe at 350 mA were 675 mA, 325 mW, and 236 mW, respectively. ϕv of the green LED was 128 lm at 350 mA. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Development of Light Sources by Large-Scale Integrated Light-Emitting Diodes

We have demonstrated large-scale integrated light-emitting diodes (LSILEDs) by using direct flip-chip bonding (DFCB) technique on a size of 30 × 40 mm2 ceramic package. Radiant flux measured at DC current of 9.1 A and forward voltage of 4.0 V was 3.3 W. Luminous flux, luminous efficacy and color-rendering index of white LED fabricated with the LSILED as the excitation source measured at DC current of 9.1 A and forward voltage of 4.0 V was 766 lm, 21.0 lm/W, and 82, respectively. The LSILED is very promising as a compact, high dense and high luminous flux white light source.

Prediction Formula of Luminous Flux Maintenance for Fluorescent Lamps with Thicknesses of Phosphor Layer and Protection Film

Minimizing our negative on the environment is a global topics of interest. Achievement of high luminous flux. Maintenance is needed for the manufacture of environmentally friendly fluorescent lamps. At first, using multiple linear regression analysis, the relation of phosphor and protective layer thickness with the luminance flux maintenance is clarified. Next, the prediction formula of luminous flux maintenance is made and it is shown that a prediction formula agree with experimental results.

Optical Simulation of Light Source Devices Composed of Blue LEDs and YAG Phosphor

The optical structures and luminous properties of light source devices composed of blue LEDs and YAG phosphor were examined using optical simulation. Results showed that the reflection-type light source device had a high luminous flux over 1.5 times greater than the transmission-type light source device. This suggests that using light reflected from the phosphor is an effective way of obtaining high output from light sources composed of LEDs and phosphor.

37.2: A Mercury‐Free Cold Cathode Fluorescent Lamp for LCD Backlighting

AbstractA mercury‐free cold cathode fluorescent lamp which is suitable for the backlighting of a car‐navigation display, has been developed. This lamp consists of one inner electrode and one outer electrode. By optimizing the structure of the electrode and the driving condition, a high luminous flux and a wide dimming control were achieved. The total luminous flux of this lamp reached to about 50% as much as that of a conventional Hg‐type CFL.

高光東電球形蛍光ランプ用の新形発光管

高光東電球形蛍光ランプ用の新形発光管