We analyze the performance of high dynamic range liquid crystal displays (LCDs) using a two-dimensional local dimming mini-LED backlight. The halo effect of such a HDR display system is investigated by both numerical simulation and human visual perception experiment. The halo effect is mainly governed by two factors: intrinsic LCD contrast ratio (CR) and dimming zone number. Based on our results, to suppress the halo effect to indistinguishable level, a LCD with CR≈5000:1 requires about 200 local dimming zones, while for a LCD with CR≈2000:1 the required dimming zone number is over 3000. Our model provides useful guidelines to optimize the mini-LED backlit LCDs for achieving dynamic contrast ratio comparable to organic LED displays.

In this study, we analyze how a backlight’s peak wavelength, full-width at half-maximum (FWHM), and color filters affect the color gamut of a liquid crystal display (LCD) device and establish a theoretical limit, even if the FWHM approaches 1 nm. To overcome this limit, we propose a new backlight system incorporating a functional reflective polarizer and a patterned half-wave plate to decouple the polarization states of the blue light and the green/red lights. As a result, the crosstalk between three primary colors is greatly suppressed, and the color gamut is significantly widened. In the experiment, we prepare a white-light source using a blue light-emitting diode (LED) to pump green perovskite polymer film and red quantum dots and demonstrate an exceedingly large color gamut (95.8% Rec. 2020 in Commission internationale de l'éclairage (CIE) 1931 color space and 97.3% Rec. 2020 in CIE 1976 color space) with commercial high-efficiency color filters. These results are beyond the color gamut limit achievable by a conventional LCD. Our design works equally well for other light sources, such as a 2-phosphor-converted white LED.

We review the emerging mini/micro-light-emitting diode (LED) displays featuring high dynamic range and good sunlight readability. For mini-LED backlit liquid crystal displays (LCDs), we quantitatively evaluate how the device contrast ratio, local dimming zone number, and local light profile affect the image quality. For the emissive mini/micro-LED displays, the challenges of ambient contrast ratio and size-dependent power efficiency are analyzed. Two figure-of-merits are proposed for optimizing the optical and electrical performances of mini/micro-LED displays.KEYWORDS ambient contrast ratio, halo effect, high-dynamic range, internal quantum efficiency, local dimming, mini/micro-LED, size effect, sunlight readability

We report high performance liquid crystal displays (LCDs), including fringe field switching (p-FFS) and in-plane switching (p-IPS), with a small average dielectric constant (ε) but positive dielectric anisotropy material. Our low ε based p-FFS and pIPS LCDs offer several attractive properties, such as high transmittance, low operation voltage, fast response time (even at −20°C), which is particularly desirable for outdoor applications of mobile or wearable display devices, and suppressed flexoelectric effect. Combining these advantages with the inherent outstanding features, such as wide viewing angle, no grayscale inversion, negligible color shift, and pressure resistance, the low ε LC based p-FFS and pIPS are strong contenders for next-generation mobile displays, and high resolution and high frame rate TVs.

Motion picture response time (MPRT) affects the image blurs of thin-film transistor (TFT) liquid crystal displays and organic light emitting diode (OLED) displays. We derive an analytical equation to correlate MPRT with the liquid crystal (LC)/OLED response time and TFT frame rate. Good agreement between our physical model and experimental results is obtained. Based on our model, we find that if the LC's response time is 2 ms or less, then its MPRT is nearly the same as that of OLED, even if OLED's response time is assumed to be 0. To achieve MPRT comparable to OLEDs, we developed an ultra-low viscosity LC mixture for the vertical alignment mode operation. The measured average gray-to-gray response time is 0.93 ms, and its MPRT at 120 Hz is 6.88 ms. In comparison, OLED's MPRT is 6.67 ms. To further shorten MPRT, we could either increase the frame rate or reduce the backlight duty ratio. Pros and cons of these approaches are discussed.