• 한국세라믹학회지
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• 제53권4호
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• pp.381-385
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• 2016

Recently, white LEDs, especially, warm white LEDs have been intensively investigated due to outstanding optical properties, long term stability and low power consumption. In this study, mixed type and patterned type of remote phosphors were prepared by screen printing process employing green and red phosphor. Each type of remote phosphor exhibited distinctive photoluminescence spectrum. For example, the mixed type of remote phosphor exhibited unique spectrum, while the patterned type showed expectable spectrum depending on the concentration of phosphors. This indicates that a small amount of red phosphor dramatically reduced the green photoluminescence in the case of mixed-type remote phosphor, whereas the effect was negligible in the patterned-type remote phosphor. The possibility of undesirable chemical reaction was further investigated by using scanning electron microscopy and X-ray diffraction.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.636-639
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• 2004

We have synthesized a $Eu^{2{\cdot}}$ -activated $Sr_3MgSi_2O_8$ blue phosphor and $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$ yellow phosphor investigated an attempt to develop white LEDs by combining it with a GaN blue LED chip. Three distinct emission bands from the GaN-based LED and the ($Sr_3MgSi_2O_8$:Eu + $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$:Eu) phosphor are clearly observed at 405nm, 455 nm and at around 540 nm, respectively. These three emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (405 nm chip)-based ($Sr_3MgSi_2O_8$:Eu + $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$:Eu) exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1338-1342
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• 2005

We have synthesized an $Eu^{2+}$-activated $Sr_3MgSi_2O_8$ blue phosphor and $Ba_2SiO_4$ green phosphor and $Ba^{2+}$ co-doped $Sr_3SiO_5$ red phosphor investigated an attempt to develop white LEDs by combining it with a GaN blue LED $chip(\lambda_{em}=405 nm)$. Three distinct emission bands from the GaN-based LED and the $(Sr_3MgSi_2O_8:Eu\; +\; Ba_2SiO_4:Eu\; +\; Ba^{2+}\; co-doped\; Sr_3SiO_5:Eu)$ phosphor are clearly observed at 460nm, 520 nm and at around 600 nm, respectively. These three emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (405 nm chip)-based $(Sr_3MgSi_2O_8:Eu\; +\; Ba_2SiO_4:Eu\; +\; Ba^{2+}\; co-doped\; Sr_3SiO_5:Eu) exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.

• Current Optics and Photonics
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• 제1권2호
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• pp.118-124
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• 2017

Color rendering index (CRI) and luminous efficacy (LE) are two key performance factors of white LEDs (WLED). While most recent works in optics focus on methodology to improve these factors, little attention has been dedicated to chemical composition of materials. This paper studies the effect of $Sr_{2.4}1F_{2.59}B_{20.03}O_{74.8}:Eu_{0.12},Sm_{0.048}$ phosphor (SrSm), in terms of concentration and particle size on CRI and LE of 8500 K - WLEDs. Importantly, the molar mass of the componential ions in SrSm are calculated to shed light on the connection between the chemical composition of the material of interest and the performance of WLEDs. Results show that CRI can be improved to a value of around 86 by boosting red-light components in WLEDs, for all 3 major configurations: conformal, in-cup, and remote phosphor. CRI value tends to decrease with larger size of particles, while LE value goes in the reverse direction. On the other hand, both CRI and LE appear to be reduced at higher concentration of SrSm. This light attenuation is analyzed by using the Lambert-Beer law and Mie-scattering theory.

• 한국통신학회논문지
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• 제37권7B호
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• pp.606-612
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• 2012

가시광 통신은 반도체 LED를 이용하여 정보를 브로드캐스트 하며, 백색광 LED는 조명과 광무선 통신을 하나의 광원을 사용하여 제공할 수 있다. 본 논문에서는 단일칩 백색광 LED를 활용하여 조명과 통신에 적합한 조명기구를 제안한다. 백생광 LED 조명기구의 구조에 따른 수평 조도특성, 무선채널 대역특성, 심볼간 간섭현상, 신호대 잡음비 및 비트 에러율을 분석함으로써 장애물이 있는 경우 제안한 LED 조명이 기존의 조명보다 우수한 조명 및 통신 채널을 제공함을 보이고자 한다.

• 한국광학회지
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• 제32권4호
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• pp.163-171
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• 2021

조명에 사용되는 일반적인 백색 발광 다이오드는 청색 발광 다이오드 위에 황색 형광체를 입힌 구조가 보편적이나 발광 스펙트럼상 짙은 적색 성분이 부족해서 조명의 연색성이 떨어지는 문제가 있다. 본 연구에서는 백색 발광 다이오드의 연색 특성을 개선하기 위해 적색 양자점 조명을 백색 조명의 확산판에 적용한 후 광학 시뮬레이션을 이용해 광구조를 최적화하고자 하였다. 양자점의 평균 자유 행정 및 확산판 내 TiO₂ 입자의 농도를 조절해 연색지수, 휘도 등 광특성을 조사했다. 대부분의 조건에서 연색지수는 90을 넘었고 이는 적색 양자점 필름의 적용이 일반적인 백색 발광 다이오드의 연색 특성을 개선하는 데 효과적인 방법임을 보여준다. 색좌표의 각도 의존성은 확산판과 조명 하단의 반사판 사이에 형성되는 광학적 공동 구조를 활용함으로써 제거할 수 있었는데 이는 공동 내 위치한 양자점 필름을 통한 빛의 다중 투과가 시야각에 따른 광경로의 차이를 줄였기 때문으로 해석된다.

• Journal of Species Research
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• 제6권1호
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• pp.68-75
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• 2017

We investigated the effects of sodium hypochlorite (NaOCl) and culture medium on embryo swelling and germination of Calanthe discolor Lindl., and established a method for determining the swelling and protocorm formation of C. discolor seeds via in vitro examination of immature seeds. Treatment of immature seeds with NaOCl greatly enhanced the extent of embryo swelling and protocorm formation of immature zygote embryos compared to seeds without NaOCl treatment. The effects of the culture media were also evaluated with regard to embryo swelling and protocorm formation of in vitro cultured seeds with and without NaOCl treatment. Additionally, the effects of white fluorescent light and red and blue LEDs lights on seedling growth in in vitro culture were examined. The most suitable condition for seedling growth after 12 weeks of culture was the red LEDs light with POM medium. These results show effective asymbiotic germination and growth of C. discolor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.375-376
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• 2007

In this work, we have simulated a 42-inch LED BLU which was based on 300 RGB LEDs. We have done an adjustment of LEDs' strip distance and a height of the top of the LED to the back of the LCD to get white color uniformity. So, we have changed simultaneously the distance between the top of the LEDs and the back of the LCD. Moreover, we set a fixed position for the horizontal of LED's pitch. And then, we have experimented and compared to our simulation data.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.22-26
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• 2013

The author analyzes the luminous efficiency of the phosphor-conversion white light-emitting diode (LED) that consists of a blue LED chip and a yellow phosphor. A theoretical model is derived to find the relation between luminous efficiency (LE) of a white LED, wall-plug efficiency (WPE) of a blue LED chip, and the phosphor absorption ratio of blue light. The presented model enables to obtain the theoretical limit of LE and the lower bound of WPE. When the efficiency model is applied to the measured results of a phosphor-conversion white LED, the limit theoretical value of LE is obtained to be 261 lm/W. In addition, for LE of 88 lm/W at 350 mA, the lower bound of WPE in the blue LED chip is found to be ~34%. The phosphor absorption ratio of blue light was found to have an important role in optimizing the luminous efficiency and colorimetric properties of phosphor-conversion white LEDs.

• 한국산학기술학회논문지
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• 제17권11호
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• pp.368-375
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• 2016

본 연구는 식물에 대한 LED 광색별 성장을 실험하여 효율적인 식물공장 광원에 대한 기준을 제시하기 위하여 수행되었다. 실험은 Red-LED와 Blue-LED, White-LED 광환경에서 식물의 성장과 이산화탄소 감소를 측정하여 확인하였다. 식물의 성장은 Red-LED에서 성장이 가장 높게 나타났다. White-LED는 Red-LED와 유사한 경향을 보였지만, 시간이 경과 할수록 Red-LED의 성장이 높은 경향을 보였다. Blue-LED는 가장 낮은 성장을 보였다. 그리고 혼합광과 단색광의 광합성정도를 확인한 결과 Red-LED와 Blue-LED를 조합한 광원에서 이산화탄소 감소가 높게 나타났으며 적색광이 많을수록 이산화탄소의 감소도 높게 나타났다. 이와 같은 실험 결과 토대로 혼합광과 백색광에서의 성장을 비교 측정한 결과, 적색 4개, 청색 2개의 비율의 광원에서 식물의 성장이 높게 나타났다. 따라서 식물공장에서 식물의 효율을 높이고 성장을 촉진하기 위해서는 백색의 단색광을 사용하는 것 보다 적색광을 사용하거나, 적색과 청색을 혼합하여 사용하여 파이토크롬 효과를 높이는 것이 바람직하다는 것이 확인되었다. 특히 백색광만 사용하는 경우 성장 초기에는 한해서 사용해야 하며 성장이 잎이 커짐에 따라 적생광이 강한 광을 사용하는 것이 효과적이다.