In recent years, Mini-LED has been widely used in direct-lit backlight for Liquid Crystal Display (LCD) widely due to its advantages of miniaturization and low power consumption. Typical Mini-LED direct-lit backlights mainly rely on the diffuser plate to convert point-like light sources into uniform surface light sources. However, the diffuser plate cannot achieve high uniformity at a very low optical distance (OD). In this paper, we introduced the pyramidal microstructure and the semi-cylindrical microstructure to both sides of the optical film, respectively. The mechanism of influence of the pyramidal microstructure and the semi-cylindrical microstructure on light was analyzed. We clarified the relationship between the parameters of the microstructure (the pyramid angle, the pyramid dimension) and the illuminance uniformity by simulation. Moreover, two layers of microstructure optical films are discussed and simulated. Through the simulation, the optical effects are evaluated and analyzed from the point of illuminance uniformity. Simulation results maintain that when the OD is 5mm, the illuminance uniformity reaches 93.07%. Compared with the diffuser plate with a thickness of 1.5mm, the thickness is reduced by 0.9mm, and the illuminance uniformity is increased by 11.77%. This work fully demonstrates the advantages of the microstructure optical film to improve the illuminance uniformity.
Micro light-emitting diode (Micro-LED) has the advantages of high brightness, low power consumption, and long life. It has great potential and broad application prospects. Using micro-LED as the light source and image source of the projection system can greatly reduce the size and power consumption of the system. However, the electrical module and the optical module of the micro-LED pico-projection system cannot be separated. This paper uses image fiber to effectively separate the electrical module and optical module in the optical engine, and designs a micro-LED pico-projection optical engine based on an image fiber. This optical engine is composed of a projection lens group, an image fiber and a micro-LED. The projection lens group is composed of 5 spherical lenses, with the total length of 6.752mm and the focal length of 2.8mm. The modulation transfer function (MTF) is higher than 0.8@32lp/mm, and the distortion is below 2%. The image fiber adopts a multi-core fiber with a diameter of 2mm and a resolution of 32lp/mm. Finally, the overall simulation model of the optical engine is built to prove its feasibility.
The key to developing a new type of liquid crystal display (LCD) lighting is to balance light quality with high light efficiency, and the light diffusion plate is an indispensable part of LCD to achieve different light extraction efficiency and light uniformity. In addition, the addition of quantum-dots (QDs) further improves the light transmittance and optical conversion efficiency of the light diffusion plate. In this paper, the surface engineering method was used to prepare QDs composites to improve the stability of QDs diffusion plate under high temperature and humidity. This paper briefly introduced the light diffusion plate, and then discusses the preparation of the QDs composites and the injection molding process of the QDs diffusion plate. Finally, the QDs diffusion plate was assembled into a backlight module, and its stability was tested at 60℃ and 85% relative humidity (RH). The experimental results show that the spectra and external quantum efficiency (EQE) of the QDs diffusion plate do not change significantly after long time storage at high temperature and humidity. This experiment improved the stability of QDs diffusion plate and lays a foundation for the subsequent large-scale production.
The surface modification strategy is widely used to solve the problems of low stability, agglomeration, surface oxidation and photoluminescence quenching of quantum dots (QDs) in practical applications. However this method can easily destroys the surface ligands of QDs, increases defects even leads to a huge loss of fluorescence. In order to improve the stability of QDs, a new synthesis method of QD-silica hybrid nanospheres was proposed in this study. These QD-silica hybrid nanospheres are characterized by using mesoporous silica spheres (MSSs) as template, adsorbing QDs as one shell, and then coating a silica layer as another shell (named SQS). The template MSSs were functionalized by (3-mercaptopropyl) trimethoxysilane (MPTMS) in order to connect MSSs and QDs. After that, the QD-adsorbed silica spheres were coated with silica as the encapsulation layer by Stober method. The structure and morphology of SQS were analyzed by TEM. The effects of different contents of MPTMS and tetraethoxysilane(TEOS) were experimentally compared. Finally, it was found that the optimal contents of MPTMS and TEOS was 250μL and 1.5mL, respectively. The luminescence intensity of SQS samples could reach 2 times higher than that of pure QD solution. Meanwhile, SQS hybrid nanospheres could avoid the tiny spots inside the microstructure caused by QD aggregation and play a better role in dispersion.
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