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.     

Development of a liquid crystal with fine‐pitch light‐source display (LFD) using an organic light‐emitting diode (OLED)

Abstract— A novel display system, refered to as an LFD (liquid crystal with fine‐pitch light‐source display) is proposed. In an LFD, an auxiliary light source patterned with a fine pitch is attached to a reflective liquid‐crystal display (LCD), and a light shield is formed on the observer's side of the light source. A vertical‐alignment LCD (VA‐LCD) is attached as the reflective LCD, and an organic light‐emitting diode (OLED) is attached as the fine‐pitch light source. An LFD can produce bright, high‐contrast images under any ambient light. A test sample was built and its display characteristics confirmed.     

A broadband wide‐incident‐angle reflective polarization converter

Abstract— A high‐performance reflective polarization converter which could be used in a backlight recycling system for liquid‐crystal‐display (LCD) devices is proposed. The device consists of a twisted‐nematic (TN) liquid‐crystal film, a uniaxial A‐plate, and a reflector. The configuration parameters, such as thickness and orientation of the films, are optimized using a genetic algorithm. As a result, the design can convert light from TM to TE polarization (or TE to TM) at a maximum 99.7%, minimum 91.3%, and average 96.7% conversion efficiency for the entire visible spectrum and incident angle from 0 to 60°. Such a broadband reflective polarization converter is particularly useful for enhancing the light efficiency and reducing the power consumption of LCDs.     

A novel polarizer‐free dye‐doped polymer‐dispersed liquid crystal for reflective TFT displays

Abstract— A novel preparation method for dichroic dye‐doped polymer‐dispersed liquid crystals has been developed. This was achieved by creating a porous polymer matrix first by washing out the liquid crystal from a polymer‐dispersed liquid crystal (PDLC), which is then refilled with dye‐doped liquid crystal. Optimizing the liquid crystal used in the refilling results in decreased turn‐on voltage and faster response time. Poster‐standard reflectivity and newspaper‐standard contrast was demonstrated with a 3.8‐in. QVGA reflective TFT display with a drive voltage of 10 V.     

Nanoparticle‐embedded polymer‐dispersed liquid crystal for paper‐like displays

Abstract— A polymer‐dispersed liquid‐crystal (PDLC) matrix template embedded with nano/microparticles can be backfilled/infiltrated with a dye‐doped liquid crystal for a paper‐like reflective display. In this way, a desirable degree of diffusion can be realized to reduce the viewing‐angle dependency of a gain reflector and metallic glare without changing other electro‐optical properties.     

Transflective twisted‐nematic liquid‐crystal display with double twisted‐nematic cell and twisted liquid‐crystal retarder

Abstract— Two configurations, (i) a double‐cell‐gap twisted nematic (DTN) liquid‐crystal display (LCD) and (ii) a single‐cell‐gap twisted‐nematic (TN) liquid‐crystal display (LCD) using a twisted LC retarder, were optimized for transflective liquid‐crystal displays. For the DTN configuration, both the single‐cell‐gap approach and the double‐cell‐gap approach were considered. The optimized configurations exhibit a high contrast ratio, wide viewing angles, and achromatic (black/white) switching in both the transmissive and reflective modes. They are easy to fabricate and also possess a perfect dark state. Both are suitable for high‐quality transflective TFT‐LCDs.     

Antiferroelectric LCD with one polarizer in a reflective configuration

A reflective antiferroelectric liquid‐crystal (AFLC) display with one polarizer is proposed. An optical retardation film was introduced into the reflective configuration to obtain enhanced electro‐optic (EO) characteristics. Numerical simulations were carried out to optimize the cell parameters so that the EO switching between the black and white states could be easily achieved. The reflective AFLC display with optimized cell parameters was found to exhibit high contrast, excellent brightness, and fast response.     

A 400‐dpi reflective storage ferroelectric liquid‐crystal display for highly readable,low‐power mobile display applications

Mobile products require longer battery lifetimes and increased information content from the display. A ferroelectric liquid‐crystal reflective storage mode was demonstrated. This display only needs updating when the image changes, resulting in ultra‐low power consumption. Passive‐matrix addressing allows for high‐resolution text to be displayed.     

A single‐cell‐gap transflective liquid‐crystal display with special electrodes

Abstract— A single‐cell‐gap transflective liquid‐crystal display with special electrodes was demonstrated. In the transmissive region, a strong longitudinal electric field was generated by decreasing the distance between the top and bottom transparent indium‐tin‐oxide electrodes; while in the reflective region, a weak longitudinal electric field is generated by increasing the distance between the top and bottom transparent indium‐tin‐oxide electrodes. And slit‐patterned electrodes were used to optimize the fringe field at the junction of the transmissive and reflective regions. As a result, both the transmissive and reflective display modes show well‐matched gray scales. The simulated single‐cell‐gap TR‐LCD has good performances.     

Transflective ferroelectric liquid‐crystal display with a single‐cell gap

Abstract— A ferroelectric liquid‐crystal (FLC) display was optimized as a transflective liquid‐crystal display (LCD). In this configuration, the single‐cell‐gap approach was considered. The optimized configuration exhibits a high contrast ratio, wide viewing angles, and achromatic (black/white) switching in both the transmissive and reflective modes. Because no double‐cell‐gap structure, no subpixel separation, and no patterning polarizers and retarders are included in the configuration, the configuration is easy to fabricate and also possess a perfect dark state. This configuration is also suitable for bistable applications.     

A silicon‐chip‐based light valve with reflective twisted‐nematic mode for high‐definition projectors

Crystalline‐silicon‐chip‐based reflective light valves are suitable for realizing high definition and bright liquid‐crystal projectors. We have developed an XGA (1025 × 769 pixels) silicon‐chip‐based light valve with a diagonal display area of 2.54 cm (1 in.). The reflective twisted‐nematic mode was examined by using the Jones matrix method as a display mode, and the normally white reflective twisted‐nematic mode was selected. This mode is suitable for a narrow cell gap, and a fast response time can be expected. In addition, the driving voltage of this mode is low and has good chromaticity with small retardation. The cell gap of the light valve is 2 μm. The cell gap support is made using spacer posts formed on the silicon chip with a photodefinable resin. The response time is 12 msec, including both rise and fall times. The contrast ratio is more than 1000 at 5 Vrms.     

A single‐substrate multicolor cholesteric liquid‐crystal display prepared through ink‐jet printing

Abstract— Ink‐jet printing was used to prepare a single‐substrate multicolor cholesteric liquid‐crystal (Ch‐LC) display incorporating three Ch‐LCs exhibiting different reflective wavelengths. A room‐temperature low‐vacuum chemical‐vapor‐deposition process was developed for coating a thin polymer film onto the Ch‐LC so that the top electrode could be coated onto the Ch‐LC layer. Herein, the successful operation of such a 10.4‐in. QVGA Ch‐LC display at 40 V will be described.     

Polymer‐based transistors used as pixel switches in active‐matrix displays

A 2‐in. active‐matrix display was demonstrated, containing 4096 solution‐processed polymer‐based transistors. By using the polymer‐dispersed liquid‐crystal display (LCD) effect, this results in a reflective, low‐power display with paper‐like contrast. The influence of the transistor parameters on the display performance is analyzed by use of a model for charging and discharging of the pixel capacitors. Good agreement was obtained between the model and the experimental data. Scaling behavior allows estimation of the performance required for transistors in a quarter‐VGA display. These requirements are met by solution‐processed pentacene transistors.     

Single‐cell‐gap transflective liquid‐crystal display and the use of photoalignment technology

Abstract— In this paper, transflective liquid‐crystal‐display (LCD) technology will be reviewed, and several new single‐cell‐gap transflective LCD configurations are proposed. Photoalignment technology is studied especially for transflective‐LCD applications. In order to realize the optimal performance of the display as well as a matched transmittance/reflectance voltage curve (TVC/RVC) for the transflective configurations, two different single‐cell‐gap transflective‐LCD approaches will be discussed. The first one is the dual‐mode single‐cell‐gap approach, in which different liquid‐crystal modes are applied to the transmissive and reflective subpixels of the transflective LCD. The other approach is the single‐mode s ingle‐cell‐gap approach, in which an in‐cell retardation film is applied to adjust the performance and TVC/RVC matching of a transflective LCD. Photoalignment technology is used to fabricate the dual‐mode liquid‐crystal cell in the first approach and also the in‐cell retardation film in the second approach. Prototypes of the proposed configurations have been fabricated, which show good performance and a matched TVC/RVC.     

A polarizer‐free flexible display using dye‐doped liquid‐crystal gels

Abstract— A reflective‐type polarizer‐free flexible display using a dye‐doped liquid‐crystal (LC) gels is demonstrated. Compared to the conventional guest‐host LC mode, it has high contrast ratio and brightness due to the combining of both scattering and absorption. Such a gel‐like flexible display is bendable and trimable. In this paper, a three‐step switch using distinct dye‐doped LC gels is also demonstrated. The potential applications are e‐paper and decorative displays.     

A dual‐cell‐gap transflective liquid‐crystal display with identical response time in transmissive and reflective regions

Abstract— A dual‐cell‐gap transflective liquid‐crystal display (TR‐LCD) with identical response time in both the transmissive and reflective regions is demonstrated. In the transmissive region, strong anchoring energy is used to decrease the response time, while in the reflective region, weak anchoring energy is used to increase the response time. And overdrive voltage technology is adopted to make the response time identical in both the transmissive and reflective regions. The device structure and operating principle of the TR‐LCD was analyzed, the anchoring energy in the transmissive and reflective regions was designed, and the response time and electro‐optic characteristics of the TR‐LCD was calculated. The simulated dual‐cell‐gap TR‐LCD demonstrated good performances.     

Single‐substrate encapsulated cholesteric LCDs: Coatable,drapable, and foldable

Abstract— The first ever, reflective cholesteric liquid‐crystal displays (ChLCDs) on single textile substrates made with simple coating processes have been developed. A novel approach for fabrication of ultra‐thin encapsulated ChLCDs with transparent conducting polymers as bottom and top electrodes will be reported. These displays are fabricated from the bottom‐up by sequential coating of various functional layers on fabric materials. Encapsulation of the cholesteric liquid‐crystal droplets in a polymer matrix and the mechanical flexibility of the conducting polymers allow for the creation of durable and highly conformable textile displays. The development and status of this next‐generation display technology for both monochrome and multicolor cholesteric displays will be discussed.     

Reflective cholesteric displays: From rigid to flexible

Abstract— Bistable reflective cholesteric liquid‐crystal displays are low‐power displays that are suitable for a variety of applications ranging from signage to high‐resolution electronic books. Recent advancements have included higher brightness, full color, black and white from a single layer, and lighting solutions. Cholesteric displays also lend themselves to simple integration into flexible materials since they may be coated and printed. We have developed reflective cholesteric displays on thin flexible plastic substrates, as well as other unconventional substrates such as paper and drapable fabrics. This paper serves as a review for recent advances in the cholesteric‐display technology at Kent Displays.     

Cell‐gap and pretilt‐angle determination of a vertically aligned reflective liquid‐crystal display

Abstract— A simple method for determining the cell gap and pretilt angle of a vertically aligned reflective liquid‐crystal display has been developed. By extrapolating the phase‐retardation curve of the VA—LC cell in the high‐voltage regime, we can determine the cell gap. With this value for the cell gap and the low‐voltage part of the phase‐retardation curve, we can determine the pretilt angle.     

Seventeen‐inch laser backlight in‐plane switching liquid crystal display with 8K, 120‐Hz driving,and BT.2020 color gamut

We have developed a 17‐inch laser backlight in‐plane switching liquid crystal display satisfying the main BT.2020 specifications, which are 8K, 120‐Hz driving, and a BT.2020 wide color gamut. The color gamut of the developed in‐plane switching liquid crystal display covers 98% of the BT.2020 wide color gamut, thanks to a laser backlight and appropriate color filters. The liquid crystal response time of 5 ms, which is sufficient for 120‐Hz driving, is achieved by adapting a faster in‐plane switching liquid crystal display, namely, the short‐range lurch control in‐plane switching liquid crystal display.