Korean Journal of Optics and Photonics (한국광학회지)

Optical Society of Korea (한국광학회)
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Antireflective Film Design to Improve the Optical Efficiency of Organic Light-emitting Diode Displays

유기발광다이오드 디스플레이의 광효율 향상을 위한 반사방지필름 설계

  • Kim, Kiman (Department of Advanced Organic Materials Engineering, Chonbuk National University) ;
  • Lim, Young Jin (Applied Materials Institute for BIN Convergence, Department of BIN Convergence Technology and Department of Polymer-Nano Science and Technology, Chonbuk National University) ;
  • Doan, Le Van (Department of Electronics Engineering, Dong-A University) ;
  • Lee, Gi-Dong (Department of Electronics Engineering, Dong-A University) ;
  • Lee, Seung Hee (Department of Advanced Organic Materials Engineering, Chonbuk National University)
  • 김기만 (전북대학교 유기신물질공학과) ;
  • 임영진 (전북대학교 BIN융합공학과 및 고분자나노공학과, 미래형BIN융합응용소재사업단) ;
  • 레 반 도안 (동아대학교 전자공학과) ;
  • 이기동 (동아대학교 전자공학과) ;
  • 이승희 (전북대학교 유기신물질공학과)
  • Received : 2018.09.07
  • Accepted : 2018.10.15
  • Published : 2018.12.25
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Abstract

In this paper, we designed a new antireflective film to improve the optical efficiency of organic light-emitting diode displays (OLEDs). The reflection characteristics in the normal and side viewing directions of OLEDs with the antireflective film were calculated, depending on the degree of polarization and transmittance of the currently used polarizer when used in the antireflective film of an OLED. The results showed that when the polarization degree of the commercial polarizer (99.990~99.995%) is lowered to 99.900%, the average reflectance of the antireflective film is increased by about 0.1% (2.5% in terms of rate of increase) which is difficult to notice with the human eye, while the transmittance is increased by 1.63~3.34% (4.2~8.2% in terms of rate of increase). This study provides an optimal design for high-light-efficiency OLEDs with good antireflection properties.

본 논문에서는 유기발광다이오드 디스플레이(OLED)의 광 효율을 향상시키기 위해 방사방지필름을 새롭게 디자인하였다. 현재 상용화되고 있는 편광판의 편광도와 투과율을 변화시켜 OLED 반사방지필름에 사용하였을 경우 정면과 측면방향의 반사특성을 계산하였다. 그 결과 편광도가 99.995%나 99.990%인 상용화된 편광판의 편광도를 99.9% 수준으로 떨어뜨릴 경우, 반사방지필름의 평균 시감반사율은 사람의 눈으로 알아차리기 힘든 약 0.1% (증가율 환산 2.5%) 상승한 반면, 투과율은 기존보다 약 1.63~3.34%(증가율 환산 4.2~8.2%) 상승하였다. 이 결과는 기존 OLED에서 저반사율을 유지하면서 광효율을 상승시킬 수 있는 광학설계 조건을 제시하였다.

Keywords

KGHHBU_2018_v29n6_262_f0001.png 이미지

Fig. 2. Optical structure of three commonly used antireflection films: (a) Normal λ/4 film using COP, (b) reverse λ/4 film using WRS, and (c) Wideband λ/4 film using COP.

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Fig. 3. R0 and Rth characteristics of three commonly used retardation films according to the wavelength.

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Fig. 4. Measured spectral transmission curves of five types of polarizers with different Ts and DOP values in MD and TD directions (xx.xx_xx.xxx means Ts and DOP values, respectively).

KGHHBU_2018_v29n6_262_f0004.png 이미지

Fig. 5. Spectral reflectance of three commonly used antireflection films.

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Fig. 6. Normalized average luminous reflectance of three commonly used antireflection films according to the viewing angle.

KGHHBU_2018_v29n6_262_f0006.png 이미지

Fig. 7. Average luminous reflectance of five types with different Ts and DOP values according to three commonly used antireflection films in normal direction.

KGHHBU_2018_v29n6_262_f0007.png 이미지

Fig. 8. Average luminous reflectance of five types with different Ts and DOP values according to three commonly used antireflection films in (a) 15°, (b) 30°, and 45° viewing angle directions.

KGHHBU_2018_v29n6_262_f0008.png 이미지

Fig. 1. (a), (c) Position and (b), (d) role of polarizer in LCD and OLED, respectively.

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