Current Optics and Photonics

Optical Society of Korea (한국광학회)
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Improving the Color Gamut of a Liquid-crystal Display by Using a Bandpass Filter

  • Sun, Yan (Department of Applied Physics, Hebei University of Technology) ;
  • Zhang, Chi (Department of Applied Physics, Hebei University of Technology) ;
  • Yang, Yanling (Department of Applied Physics, Hebei University of Technology) ;
  • Ma, Hongmei (Department of Applied Physics, Hebei University of Technology) ;
  • Sun, Yubao (Department of Applied Physics, Hebei University of Technology)
  • Received : 2019.08.06
  • Accepted : 2019.09.09
  • Published : 2019.12.25
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Abstract

To improve the color gamut of a liquid-crystal display (LCD), we propose a bandpass filter that is added to the backlight unit to optimize the backlight spectrum. The bandpass filter can only transmit red, green and blue light in the visible range, while reflecting the unwanted light. We study the optical properties of the bandpass filter using the transfer-matrix method, and the effect of the bandpass filter on the color gamuts of LCDs is also investigated. When a bandpass filter based on a 5-layer configuration comprising low and high refractive indices ((HL)2H) is used in phosphor-converted white-light-emitting diode (pc-WLED), K2SiF6:Mn4+ (KSF-LED), and quantum-dot (QD) backlights, the color gamuts of the LCDs improve from 72% to 95.3% of NTSC, from 92% to 106.7% of NTSC, and from 104.3% to 112.2% of NTSC respectively. When the incident angle of light increases to 30°, the color gamuts of LCDs with pc-WLED and KSF-LED backlights decrease by 2.9% and 1% respectively. For the QD backlight, the color gamut almost does not change. When the (HL)2H structure is coated on the diffusion film, the color gamut can be improved to 92.6% of NTSC (pc-WLED), 105.6% of NTSC (KSF-LED), and 111.9% of NTSC (QD). The diffusion film has no obvious effect on the color gamut. The results have an important potential application in wide-color-gamut LCDs.

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References

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