Hui-Chuan Cheng

Extended Kerr effect of polymer-stabilized blue-phase liquid crystals

Electric-field-induced birefringence of a polymer-stabilized blue-phase liquid crystal (BPLC) is investigated. In the low field region, conventional Kerr effect holds. As the electric field increases, the induced birefringence gradually saturates and deviates from Kerr effect. An exponential convergence model, called extended Kerr effect, is proposed to fit the experimental data. Good agreement between experiment and model is obtained. This extended Kerr effect will make a significant impact to the optimization of emerging BPLC display devices.

Polymer-stabilized optically isotropic liquid crystals for next-generation display and photonics applications

Polymer-stabilized optically isotropic liquid crystals, including blue phases, are emerging as a strong contender for next-generation display technology because they exhibit some revolutionary features such as no need for surface alignment, submillisecond response time, isotropic dark state, and cell gap insensitivity. The basic material properties, including electric field-induced birefringence, dispersion relation of Kerr constant, and temperature dependent Kerr constant, are reviewed. Recent progress on blue phase liquid crystal material development and device structures for lowering the operating voltage are introduced. Promising applications and remaining technical challenges are also discussed.

Vertical field switching for blue-phase liquid crystal devices

A low-voltage (  80%), submillisecond-response, and hysteresis-free polymer-stabilized blue-phase liquid crystal (BPLC) device with vertical field switching (VFS) and oblique incident light are demonstrated experimentally. Unlike the commonly employed in-plane switching in which the electric field is primarily in lateral direction and not uniform spatially, the VFS mode has uniform longitudinal field. As a result, the operating voltage is reduced by ∼ 3.2 × which in turn helps to eliminate hysteresis. The VFS mode is a promising candidate for the emerging BPLC display and photonic devices.

Low Voltage Blue-Phase LCDs With Double-Penetrating Fringe Fields

A blue-phase liquid crystal display (BP-LCD) with an in-plane switching (IPS) electrode and etched substrate for generating double-penetrating fringe fields is proposed. An etching depth of 1-2 helps to lower the operating voltage by 30%. This etched IPS BP-LCD also exhibits a wider viewing angle than the conventional one because of the created multi-domain structures in the etched areas. Physical mechanisms responsible for the observed phenomena are discussed.

Blue-Phase Liquid Crystal Displays With Vertical Field Switching

A low-voltage, high-transmittance, hysteresis-free, and submillisecond-response polymer-stabilized blue-phase liquid crystal (BPLC) display with vertical field switching (VFS) and oblique incident light is demonstrated. In the VFS mode, the electric field is in longitudinal direction and is uniform. By using a thin cell gap and a large oblique incident angle, the operation voltage is significantly reduced which plays a key role to eliminate hysteresis and residual birefringence. The VFS mode is a strong contender for the emerging BPLC display and photonic devices.

Color Breakup Suppression in Field-Sequential Five-Primary-Color LCDs

Field-sequential-color liquid crystal displays (FSC LCDs) exhibit a ~ 3× higher optical efficiency and 3× higher resolution, but the color breakup (CBU) degrades the image quality and limits the practical applications. In this paper, we propose a method to reduce CBU by using five-primary LEDs instead of three. Without increasing the sub-frame rate as three-primary LCDs, we can suppress the CBU by utilizing proper color sequence and weighting ratios. The color gamut achieves 140% NTSC and the white brightness increases by more than 13%, as compared to the three-primary LCDs.

Wide-View Vertical Field Switching Blue-Phase LCD

We report three major approaches for improving the contrast ratio and viewing angle of a vertical field switching (VFS) blue-phase liquid crystal display (BPLCD). The first approach involves compensation films, the second one uses wire-grid polarizer, and the third one employs an E-type analyzer. Our simulation results show that a contrast ratio over 1000:1 can be achieved. For wide-view applications, we could use a diffuser or curved turning film to steer the high contrast images to different viewing angles.

Time-Multiplexed Dual-View Display Using a Blue Phase Liquid Crystal

A time-multiplexed dual-view display device using a blue phase liquid crystal is proposed. In this design, a vertical field switching blue phase liquid crystal display (VFS-BPLCD) panel is used to achieve high transmittance and fast response. Combined with a directional backlight module, this device can present two different images to viewers sequentially. The proposed device has advantage in full spatial resolution.

Turning film for widening the viewing angle of a blue phase liquid crystal display

We report a new turning film structure for widening the viewing angle of a vertical-field-switching blue-phase liquid crystal display, which employs a directional backlight. The turning film consists of periodic prismatic structures: each period has three prisms with different base angles so that the output light can be spread to a larger angle. Simulation results show that a full width at half-maximum of ±80° in the horizontal direction and ±45° in the vertical direction can be achieved.

Fast-Response Blue-Phase Liquid Crystal for Color-Sequential Projection Displays

Color sequential projection display using a vertical field switching (VFS) polymer-stabilized blue phase liquid crystal (BPLC) is proposed. The VFS-BPLC exhibits submillisecond response time which is useful for suppressing color breakup. The proposed projector also has a small throw ratio. With phase compensation, the distortion from oblique LC panel could be corrected.