Blue Laser Diode와 고출력 LED에 적용 가능한 Phosphors in Glass 제조 및 이중반사형 해상용 LED 등명기 광학 설계

Abstract

Light emitting diodes(LEDs) have been developed as a major light source in diverse application of illumination and are still investigated widely for improving their high power and high efficiency. As a part of development of light source, blue laser diodes(LD) based white lights source becomes a next generation light source in illumination and display applications. Generally, white light can be generated from yellow emitting phosphors irradiated by blue emitting devices. However, the present LD based white light source technique has a significant problem, thermal quenching of the phosphor. Therefore, improving phosphor stability under high temperature is a rising question. To solve this problem, synthetic inorganic materials including phosphor in glasses (PiGs) have been suggested as alternative proximate phosphor types. In this study, we synthesized PiGs composed of the tellurite glasses (TeO2–ZnO–B2O3–BaO) and Ce:YAG phosphor, and evaluated stability of these PiGs. The procedure of PiG synthesis consists of two steps, (1) preparation of mixture of tellurite glasses and Ce:YAG phosphor, and (2) fabrication of PiG via remelting the mixture. In the first step, to produce matrices, the tellurite glasses (TeO2–ZnO–B2O3–BaO) were prepared by melting the mixtures of raw materials in alumina crucibles at 1000 °C for 30 min using the combinatorial melting system. The melts were quenched on a copper plate. The synthesized glasses were crushed for obtaining the cullet with the size below 100 μm. Collected cullet were mixed with Ce:YAG phosphor. The second step is to re-melt the phosphors-mixed glass cullet at low temperature in order to prevent degradation of the phosphors during melting. Synthesized PiGs were polished at the desired thickness. PiG samples ware showed good visible transparency. The photoluminescence excitation and emission spectra of PiG samples were similar to those of Ce:YAG phosphors. The white LEDs which were fabricated by blue LED chip(460 nm) and 2.5 mm thickness of PiG(Ce:YAG 10 wt.%) exhibited the CIE 1931 chromaticity coordinates of 0.217,0.205. PiG samples were irradiated to 1.5 W blue laser. The white light intensity slightly decreased up to 10 min, and then was stabilized. Marine lanterns are installed on light buoys for safe navigation of ships. Marine lanterns used oil in the beginning of 1900 and the light bulb in the 1950s. Since 2003, the LED marine lantern has been developed. However, only ordinary bulbs are replaced with LEDs, but the installation and configuration remain the same. Fresnel lenses are used for transmitting light in parallel. Fresnel lenses are difficult to design and require high cost. Therefore we replaced the Fresnel lens to a reflector in the marine lantern. Illumination optics design program(LightTools) was used for simulation the light distribution according to the LED-200 standard for marine lantern. The LED module of cross type using 5 LED chips with 3 W was calculated as 441.7 cd in the simulation that satisfied the average horizontal brightness of the LED-200 standard. The LED module using 4 LED chips with 13 W was calculated as 672.3 cd. As a result, the power consumption of the simulated LED module using 3 W LED chip in was 78.3% lower than 24 W of LED-200 standard. And the power consumption of the Simulated LED module using 13 W LED chip in was 56.7% lower than 24 W of LED-200 standard.