Yi-Jun Wang

Improved Kerr constant and response time of polymer-stabilized blue phase liquid crystal with a reactive diluent

A polymer-stabilized (PS) blue phase liquid crystal (BPLC) with fast response time and large Kerr constant is investigated by doping a low molecular weight monomer (N-vinylpyrrollidone) into a conventional PS-BPLC consisting of BPLC, RM257, and 1,1,1-trimethylolpropane triacrylate. With this polymer network system, Kerr constant and the response can be improved simultaneously. Compared to the conventional PS-BPLC, Kerr constant of the proposed PS-BPLC can increase by 54% and the response time can decrease by 23% at the same time. The contrast ratio can be kept at a high level, over 1000:1 at λ = 633 nm.

Blue Phase LC/Polymer Fresnel Lens Fabricated by Holographics

A novel fabrication method using holographic exposure for switchable blue phase (BP) liquid crystal (LC)/polymer Fresnel lens was demonstrated. The Fresnel pattern can be achieved by interfering a planar and a spherical wave fronts with a 532-nm laser. The BPLC/polymer Fresnel lens can thus be fabricated without photo mask and controlled with a simpler driving compared with the conventional LC Fresnel lens.

High directional backlight using an integrated light guide plate.

A high directional backlight system that combined a composite microstructure light guide plate (LGP) with a collimated light source was proposed for eco-displays. The collimated planar light was expanded from a point light source and guided towards the normal direction by utilizing the micro-prism array on LGP. High uniformity of spatial luminous, 91%, with a narrow viewing cone of ± 4° can be achieved without additional optical films. Moreover, compared to the conventional backlight, only 5% of power consumption was needed to keep the same luminance, hence, the optical efficiency increased by a factor of 1.47.

Critical temperature in phase transition of blue phase liquid crystal

A critical temperature is found in the phase transition of blue phase liquid crystal (BPLC), which affects the electro-optical properties and polymer stabilization of polymer stabilized BPLCs (PSBPLCs). The relation between lattice formation process of BPLCs and the temperature is also demonstrated showing that the heterogeneous lattice generation and the homogeneous lattice growth dominate the different temperature ranges in phase transition process. With different cooling rates, the material properties of BPLCs change as the result of different stages of heterogeneous lattice generation and homogeneous lattice growth.

Efficiency Enhancement of Organic Light-Emitting Diodes on Flexible Substrate With Patterned Inverted Conical Structure

The total internal reflection effect in conventional electroluminescent devices causes a large amount of light energy to be trapped in devices and induces heat energy that adversely affects the performance of the device. To enhance the light outcoupling efficiency without sacrificing the electrical properties, a patterned inverted conical (PIC) structure fabricated by a focused femtosecond laser on a flexible substrate was demonstrated. Compared with the conventional flexible organic light-emitting diode (OLED), the OLED with the PIC structure exhibited a current efficiency increase of a factor of 2.6 with no emission spectrum altered. In addition, the flexible OLED with PIC substrate can avoid the mirror reflection effect under the strong ambient light for a better visual experience. This highly effective method is compatible with the current device fabrication process and is applicable for full-color OLED display and lighting.

One Glass Single ITO Layer Solution for Large Size Projected-Capacitive Touch Panels

One glass single ITO layer solution has been demonstrated for large size projected-capacitive touch panels. Using simple touch sensors and algorithm, the proposed solution can effectively solve the issues of sensitivity reduction and large coordinate shifting existing in current large size touch panels. A touch system based on the proposed solution can achieve a coordinate shifting of less than 1.5%.

A Transflective Display Using Blue Phase Liquid Crystal

A combined fringe and in-plane switching (FIS) mode single-cell-gap transflective display using blue-phase liquid crystal (BPLC) is proposed. The structure makes use of the space above the pixel electrodes of this FIS mode as reflective regions and the space between pixel electrodes as transmissive regions. The structure which can be optimized to balance the optical phase retardation between transmissive region and reflective region with simple fabrication process exhibits relatively high optical efficiency and well matched voltage of transmittance and reflectance curves.

Switchable viewing angle display with a compact directional backlight and striped diffuser.

A compact high-directionality backlight module combined with a striped diffuser is proposed to achieve an adjustable viewing angle for eco-display. The micro-prisms on the compact light guide plate guide the emitting rays to the normal viewing angle, whereas a set of striped diffusers scatter the rays to a wide viewing angle. View cones of ± 10° / ± 55° were obtained for narrow/wide viewing modes with 88% / 85% uniformity of spatial luminance, respectively. Compared with the conventional backlight, the optical efficiencies were increased by factors of 1.47 and 1.38 in narrow and wide viewing modes, respectively. In addition, only 5% of power consumption was needed when the backlight worked in private narrow viewing mode to maintain the same luminance as that of a conventional backlight.

Scanning Prism with Polymer-Stabilized Blue Phase Liquid Crystals

A scanning prism with polymer-stabilized blue phase liquid crystals (PS-BPLCs) was demonstrated with an impulsive blinking backlight system of high-resolution three-dimensional (3-D) display. The fast switching PS-BPLC prism, whose response time was less than 1 ms, may solve the resolution degradation problem for the autostereoscopic display. Also, the impulsive blinking backlight system may improve the dynamic crosstalk for 3-D perception. By optimizing the device structure and backlight system, the scanning prism-type autostereoscopic display may achieve low crosstalk, about 14%, for high-resolution 3-D display.

Light extraction from electroluminescent devices using micro-rod array embedded within glass substrate.

The total internal reflection (TIR) effect in conventional electroluminescent devices causes a large amount of light energy trapped in the devices and result in heat energy 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 organic light-emitting diodes were employed to verify the effect of the proposed method, which increases out-coupling efficiencies by a factor of 1.9, 1.7, and 1.82, respectively, compared with conventional devices. This highly effective method is compatible with current device fabrication processes and is applicable to full-color electroluminescent devices.