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Research On High Efficiency Integrated Display Device And Its Applications

Posted on:2016-07-12Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y J WangFull Text:PDF
GTID:1108330503493774Subject:Electronic Science and Technology
Abstract/Summary:PDF Full Text Request
Display systems embedded within the electronic products such as wearable devices, smart phones and tablets not only provide the information to users but also play a critical role in vast applictions. Nevertheless, the performance of current display system, whether LCD or OLED, are still far from the desired level. Low optical efficiency, large form factor were still the among the issues and limited them for widly applications.In the dissertation, the basic research on high efficiency backlight module and OLED out-coupling efficiency enhancment were thoroughly investigated. Moreover, applications based on high collimated backlight and high efficiency OLED were also demonstrated. 1. Collimated backlight with high optical efficiencyTo increase the optical efficiency of backlight, two kinds of high directional backlights(double-wedged type and planar trapezoid type) were demonstrated. The collimated planar light was expanded from a point light source and guided towards the normal direction by utilizing the micro-prism array on Light Gudie Plate(LGP). Compared with the conventional backlight module, the novel configuration can achieve high uniformity(>90%) with the optical efficiency increased by a factor of 1.47 without additional optical films. It can offer FWHM at ±4° in dual directions with only 5% power consuming of conventional backlight at the same luminance. 2. Applications based on collimated backlight(Switchable viewing angle display &multi-view autostereoscopic display)In order to expand the applications of high directional backlight, a switchable viewing angle display with a compact high-directionality backlight and striped diffuser has been demonstrated for eco-display. The micro-prisms on LGP guide the emitting rays to the normal viewing angle, whereas a set of striped diffusers scatter the rays to a wide viewing angle. Compared with the conventional backlight module, the proposed construction exhibited the optical efficiency increased by a factor of 1.38 with a spatial uniformity 85% in the Wide Viewing Angle(WVA) mode and a factor of 1.47 with a spatial uniformity 88% in the Narrow Viewing Angle(NVA) mode. It can offer ± 55° of FWHM in the WVA mode, which is similar to that of the conventional backlight and offer ±10° of FWHM in the NVA mode which consumes only 5% power to maintain the same luminance as a conventional backlight.In addition, the exploratory research for autostereoscopic display with collimated backlight was also investigated. By utilizing the refractive effect of micro-prism on the collimated backlight, two-view and multi-view autostereoscopic displays were proposed. The system performance was simulated by the ray tracing software to provide a novel way to design on auto-stereoscopic display. 3. Basic research on OLED out-coupling efficiency enhancementThe TIR effect in conventional electroluminescent devices causes a large amount of light energy trapped in the devices and result in heat that adversely affects the performance of the device. In order to enhance the light out-coupling efficiency without sacrificing the electrical properties, a micro-rod array(MRA) structure fabricated by a femtosecond laser was demonstrated. Green, blue, and red OLEDs on an MRA-glass substrate exhibited an out-coupling efficiency enhancement by a factor of 1.9, 1.7, and 1.82, respectively, at 10 mA/cm2 compared to conventional OLEDs. The results indicate the optical performance can be improved by only one MRA structure for full-color OLEDs, while the light distribution with an MRA substrate was close to that of Lambertian light source. In addition, the patterned inverted cone(PIC) structure was also proposed to enhance the out-coupling efficiency for flexible OLED. The light distribution can be modified by the different depth-to-width ratio of PIC with laser irradiation. The optical efficiency was increased by a factor of 2.4 with the 33.4% density of PIC. The proposed method, which is compatible with current fabrication processes, effectively enhances optical out-coupling efficiency for both rigid as well as flexible OLED. 4. Applications based on high efficiency OLED(Localized 2D/3D switchable display)A novel backlight module that integrates dual layer strip patterned organic light emitting diode(DLSP-OLED) for 2D/3D switchable display was demonstrated. The DLSP-OLED functions as a parallax barrier in 3D mode and a planar light source in 2D mode. This configuration can function localized 3D display by modulating the DLSP-OLED individually simply to meet consumers’ various demands. The backlight module with a thin form factor(~20% thickness compared with origional structure) can achieve uniformity of 91% in 2D mode, and increased optical efficiency by a factor of 2 in 3D mode with a small crosstalk(>5%), compared with the conventional 2D/3D switchable display.
Keywords/Search Tags:Collimated backlight, switchable viewing angle, multi-view autostereoscopic display, OLED out-coupling, localized 2D/3D switchable display, optical design
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