Transflective Liquid Crystal Display Research Articles

Simulation study of single‐cell‐gap transflective liquid crystal display with nonuniform potential

A single‐cell‐gap transflective liquid crystal display with a nonuniform electric potential is demonstrated. The top substrate has a top planar common electrode, a transparent dielectric layer with a general dielectric constant is coated on the bottom substrate, and two planar pixel electrodes with the same size are coated on the dielectric layer and the bottom substrate, respectively. With the different gaps between the two planar pixel electrodes and top planar pixel electrode, the nonuniform electric potential from the transmissive region (T region) to the reflective region (R region) is generated, while a bumpy reflector is coated under the bottom substrate. In this device, with the dielectric layer, the pixel and common electrodes generate a strong electric potential in the T region and a relatively weak electric potential in the R region. Consequently, the T and R regions accumulate the same optical phase retardation. The simulation results show that the display exhibits reasonably low operating voltage, high optical efficiency, and well‐matched voltage‐dependent transmittance and reflectance curves. Besides, the fabrication process and the driving mode of the transflective liquid crystal display are relatively simple, and it is suitable for mobile applications.

A simple transflective liquid crystal display with composite dielectric layer

ABSTRACTA simple transflective liquid crystal display with a vertically aligned cell using a composite dielectric layer is demonstrated. The top substrate has a top planar common electrode, two transparent dielectric layers with different dielectric constants are coated on the bottom planar pixel electrode to generate linearly varying electric potential from the transmissive region (T region) to the reflective region (R region), while two bumpy reflectors are coated under the bottom substrate. In this device, with the composite dielectric layer, the common and pixel electrodes generate a strong electric potential in the T region and a relatively weak electric potential in the R region. Consequently, the T and R regions accumulate the same electro-optical characteristics. The simulation results show that the display exhibits reasonably low operating voltage, high optical efficiency and well-matched voltage-dependent transmittance (VT) and reflectance (VR) curves. Besides, the driving mode and the fabrication process of the transflective liquid crystal display are fairly simple and it is suitable for mobile applications.

Transflective blue-phase liquid crystal display with dielectric protrusion

ABSTRACTA transflective blue-phase liquid crystal display (TRBP-LCD) with dielectric protrusions is proposed. The dielectric protrusions are fixed on the in-plane-switching (IPS) electrodes. The potential drops very slowly in the dielectric protrusions, thus the total field penetrating depth is significantly enlarged and the operating voltage is lowered, which helps suppressing electrostriction effect. The different heights of the dielectric protrusions in the transmissive (T) and reflective (R) regions contribute to balance the optical phase retardation between the T and R regions. The simulation results verify that the proposed TRBP-LCD can achieve low operating voltage and good sunlight readability.

A single-cell-gap transflective liquid crystal display with a vertically aligned cell

ABSTRACTA single-cell-gap transflective liquid crystal display with a vertically aligned cell using square ring electrode is demonstrated. The top substrate has a top planar common electrode, a square ring pixel electrode is coated on the bottom substrate, while a bumpy reflector is coated under the bottom substrate. In this device, the planar common electrode and square ring pixel electrode generate a strong longitudinal electric field in the transmissive region (T region) and a weak fringe field in the reflective region (R region). As result, the T and R regions accumulate the same optical phase retardation. The simulation results show that the display exhibits reasonably low operating voltage, high transmittance and well-matched voltage-dependent transmittance and reflectance curves. Besides, fabrication process of the transflective liquid crystal display is very simple.

Enhancement of surface anchoring energy in low power consumption transflective liquid crystal displays with three display modes

Power consumption saving in transflective liquid crystal displays (TR-LCDs) with three display modes was proposed in our previous study [1]. Two of the display modes in the TR-LCD are designed to reduce power waste in common TR-LCD under dim/strong ambient lights environment. The required surface anchoring energy (SAE) of the previous design (2.0436×10−5 J/m2) is too weak for practical fabrication processes. The SAE of the new TR-LCD proposed in the current work is increased to 1.2238×10−4 J/m2. However, the tradeoff is the relatively high operation voltage, which is effectively reduced by compensation films (CMPFs). The design of CMPFs and the impact of cell gap and SAE errors on the dark state of TR-LCDs are investigated in detail. Comparisons between our previous work and the current study are also made. Further discussions on power saving concept of the TR-LCD are given in detail. Moreover, the fabrication example to approach such TR-LCDs using dual-pretilt-angle method based on photo manners is proposed. The reported results can give useful references about CMPFs design for TR-LCDs and/or other types of LCDs.

A transflective polymer-stabilised blue-phase liquid display with partitioned wall-shaped electrodes

ABSTRACTA transflective polymer-stabilised blue-phase liquid crystal display (BP-LCD) with partitioned wall-shaped electrodes is proposed. The etched polymer layer contributes to balance the optical phase retardation between transmissive (T) and reflective (R) regions. The partitioned wall-shaped electrodes generate uniform and horizontal fields throughout the entire LC layer to induce isotropic-to-anisotropic transition in the blue-phase liquid crystal medium through Kerr effect. Consequently, the accumulated phase retardation along beam path is large, resulting in reasonable low operation voltage and high transmittance both in T and R regions. This approach enables the BP-LCD to be addressed by amorphous silicon thin-film transistors. Moreover, it exhibits wide viewing angle and a well-matched gamma curve.

A transflective blue-phase liquid crystal display with alternate electrodes

ABSTRACTA transflective polymer-stabilised blue-phase liquid crystal display (BP-LCD) with alternate electrodes is proposed. The alternate electrodes are composed of right triangle electrodes and slanted electrodes. To balance the optical phase retardation between the transmissive (T) and reflective (R) regions, the legs of the right triangle electrodes in the T region generate uniform horizontal electric field, the hypotenuses of the right triangle electrodes and slanted electrodes in the R region generate uniform oblique electric field. As result, the T and R regions obtain the same optical phase retardation. This display exhibits reasonably high transmittance, low operating voltage, wide viewing angle and well-matched voltage-dependent transmittance and reflectance curves.

Concept of power consumption saving in transflective liquid crystal displays

ABSTRACTThis study proposes the concept of power consumption saving in transflective liquid-crystal displays (TR-LCDs). This concept is based on the design of a TR-LCD with three different display modes, namely, transmissive (T), reflective (R) and transflective (TR). Among the three, the TR mode is most often used to operate the designed LCD. To conserve power and extend the battery life, the designed LCD can be switched to operate in T/R mode in an environment with dim/stable ambient light. The highest operation voltages of both T and R modes are less than half of that of the TR mode. Moreover, the strong and weak surface anchoring energies that affect TR-LCD performance and the various pretilt angles of LCs are discussed. Moreover, the operating voltage (3.7 V) to obtain the good dark state of the three modes is independent of the errors of cell gap fabrication and surface anchoring energy, and temperature effect. The concept can be applied to portable electronic gadgets in which power consumption is an important issue.

Optical simulation of single-cell-gap transflective liquid crystal displays based on surface anchoring energy of periodical nano-grooved structures.

The single-cell-gap transflective liquid crystal display (TR-LCD) based on periodic distribution of surface anchoring energy (SAE) of periodical nano-grooved structures is reported in this study. Different SAEs of planar-aligned nematic LC cells are associated with the threshold and operation voltages of the adopted LCs. Thus, according to the transmittance versus applied voltage curves, the regions with strong and weak SAEs in LC cells can be the transmission and reflection regions of a TR-LCD, respectively. According to the simulation results using 1D-DIMOS software, the phase retardation of a strong SAE region is approximately twice as large as that of a weak SAE region when a specific voltage is applied, and a suitable difference in SAE exists between these two regions. Moreover, various SAEs based on periodical nano-grooved structures can be fabricated to demonstrate the TR-LCD.

Low voltage transflective blue-phase liquid crystal display with a non-uniform etching substrate**Project supported by the National Natural Science Foundation of China (Grant Nos. 61535007 and 61320106015) and the National Basic Research Program of China (Grant No. 2013CB328802).

A transflective polymer-stabilized blue-phase liquid crystal display (BP-LCD) with a non-uniform etching substrate is proposed. In-plane switching (IPS) electrodes on the bottom substrate are put on the different gaps, and the bottom substrate between the electrodes is etched into different depths in transmissive (T) and reflective (R) regions. This structure can balance the optical phase retardation in the two regions and is helpful to achieve well-matched voltag-dependent transmittance and reflectance curves. This transflective display has high optical efficiency, a wide viewing angle, and low operating voltage (approximately 6 V).

Unitary Transflective Liquid Crystal Display with an In-Cell Retarder on a Wire Grid Plate as a Reflector–Polarizer in a Single Driving Configuration

Unitary Transflective Liquid Crystal Display with an In-Cell Retarder on a Wire Grid Plate as a Reflector–Polarizer in a Single Driving Configuration

Unitary Transflective Liquid Crystal Display with an In-Cell Retarder on a Wire Grid Plate as a Reflector–Polarizer in a Single Driving Configuration

A unitary type of a transflective liquid crystal display (LCD), having the same optical efficiency in both the transmissive (T) part and the reflective (R) part, is developed using an in-cell patterned (IP) retarder fabricated directly on a wire grid (WG) plate in a twisted-nematic geometry. The WG plate is used for a substrate and served as a polarizer in the T region and a reflector in the R region. In this unitary transflective LCD, it was found that the high optical efficiency and the fast response are easily achieved in a single driving scheme since the electro-optical disparity between the transmittance and the reflectance is intrinsically eliminated.

A Single-Cell-Gap Transflective Dual-Mode Liquid Crystal Display

A transflective dual-mode liquid crystal display (LCD) featuring single-cell-gap structure has been proposed in this paper. Unlike transflective single-mode LCDs, dual-mode LCD can work as either monostable transmissive or bistable reflective LCDs in a sense that two different modes of display are unified in one device. We have confirmed that it has not only desirable electro-optical performance but also longtime memory ability.

Single cell gap polymer-stabilized blue-phase transflective LCDs using internal nanowire grid polarizer

Optically isotropic liquid crystal (LC) mixture such as blue-phase LC and nanostructured LC composites exhibit the advantages of fast response time, high contrast ratio and wide-viewing angle due to the induced birefringence along the horizontal electric field. Utilizing this mixture, a novel single cell gap in-plane switching-type polymer-stabilized blue-phase transflective liquid crystal display by embedding the nanowire grid polarizer as a polarization-dependent reflective polarizer in the R region is proposed. This device can be used as a normal black mode without any quarter-wave plate or patterned in-cell phase retarder. Moreover, the transmittance is identical to the reflectance so that it will be suitable for single gamma driving. Detailed electro-optic performances, such as voltage-dependent light efficiency and viewing angle of the proposed device configuration, are investigated.

Transflective Blue-Phase Liquid Crystal Display Using an Etched In-Plane Switching Structure

A transflective polymer-stabilized blue-phase liquid crystal display (BP-LCD) using an etched in-plane switching (IPS) structure is proposed. To balance the optical phase retardation between the transmissive ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> ) - and reflective ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> ) -regions, IPS electrodes are formed with the same dimensions in both <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> - and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> -regions, and the substrate between the electrodes is etched for generating double-penetrating fringe fields only in the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> -region . This display exhibits a reasonably wide viewing angle and well-matched voltage dependent transmittance and reflectance curves.

Single Pixel Transflective Liquid Crystal Display with Cholesteric Half Mirror

We propose a transflective liquid crystal display (LCD) operated in a whole pixel configuration consisting of the single-polarized LC cell and the broadband cholesteric LC (ChLC) half mirror. The broadband spectrum ChLC film is used for a polarization-sensitive mirror which reflects a given circular polarization but transmits its orthogonal polarization. Our transflective LCD can be demonstrated by just replacing the polarizer, placed toward a backlight unit in the conventional cross-polarized LC modes, with the ChLC half mirror.

A single‐cell‐gap transflective liquid‐crystal display using different pretilt angles in transmissive and reflective regions

Abstract— A single‐cel l‐gap transflective liquid‐crystal display with two types of liquid‐crystal alignment based on an in‐plane‐switching structure is proposed. The transmissive region is almost homeotropically aligned with the rubbed surfaces at parallel directions while the reflective region has a homeotropic liquid‐crystal alignment. For every driving voltage for a positive‐dielectric‐anisotropy nematic liquid crystal, the effective cell‐retardation value in the transmissive region becomes larger than that in the reflective region because of optical compensation film which is generated by low‐pretilt‐angle liquid crystal in the transmissive region. Under the optimization of the liquid‐crystal cell and alignment used in the transmissive and reflective areas, the transmissive and reflective parts have similar gamma curves. An identical response time in both the transmissive and reflective regions and a desirable viewing angle for personal portable displays can also be obtained.

Single pixel transmissive and reflective liquid crystal display using broadband cholesteric liquid crystal film

We propose a single mode transflective liquid crystal display (LCD) which is operated as the transmissive and reflective modes in a single pixel without dividing into sub-pixels. The single pixel transflective LCD was composed of the cross-polarized nematic LCD as a light modulator and the broadband cholesteric liquid crystal film (BCLCF) as a half mirror. The BCLCF, simply prepared by the exposure of ultraviolet light to the mixture of the nematic LC and the reactive mesogen with chirality, selectively reflects a certain circular polarization but transmits the orthogonal circular polarization in entire visible light. The electro-optical properties in both transmissive and reflective modes coincide with each other.

Single-cell gap-transflective liquid crystal display using two optical modes of a bistable liquid crystal

We present a single-cell gap-transflective liquid crystal display (LCD) characterized by a π cell having bulk-type liquid crystal (LC) bistability and an optical film configuration. The π cell has two stable states, which are a twisted and a nontwisted LC state. We used the twisted LC state for the reflective part connected with nonpatterned electrodes, producing a vertical field in the proposed transflective LCD. Also the nontwisted LC state was for the transmissive part with interdigitated patterned electrodes driving an in-plane field in the device. The simulated and experimental results show good electro-optical characteristics in both the reflective and transmissive parts.

Transflective fringe-field switching liquid crystal display without any retarder

Conventional transflective liquid crystal displays (LCDs) with single cell-gap requires optical compensation films or patterned retarders to balance the optical path-length difference between transmissive and reflective regions. In this paper, novel single cell-gap transflective LCDs driven by fringe electric field without using the compensation film or in-cell retarder have been proposed. The liquid crystal director is aligned parallel to analyzer but makes an angle of 45° with respect to analyzer in reflective region. In addition, the surface pretilt angle in the reflective region is controlled by vertical field and polymerization of an UV curable reactive mesogen at the same time and thus, the effective cell retardation in the reflective region becomes smaller than that in transmissive region. Consequently, without using any compensation film or in-cell retarder, the single cell-gap and single-gamma transflective LCD with high performance is realized.