Polymer-dispersed Liquid Crystal Display Research Articles

Doping white carbon black particles to adjust the electro-opticical properties of PDLC

ABSTRACT Polymer-dispersed liquid crystal (PDLC) is a possible active matrix transparent display technology due to its high transparency, good visibility, and low-power consumption. This paper examined the morphology of polymer-dispersed liquid-crystal materials (PDLCs), which show great potential for display applications. The materials were blends of an eutectic nematic liquid-crystal mixture and a UV-cross-linkable polymeric matrix. White carbon black nanomaterials with high surface adsorbability, high purity, and good stability are ideal materials for the driver circuit of the PDLC display. The influence of the ratio between polymerised monomers and between polymerised monomers and liquid crystals on the electro-optical properties of PDLC system had been studied. We explored the doping of white carbon black nanomaterials in the liquid crystal polymer systems. To achieve this, we have taken advantage of the liquid crystal electro-optical effect experimental instrument to study a series of electro-optical parameters of PDLC, using also additional information on the nanodroplet size and shape distribution provided by SEM images of the PDLC cross-section.

Polymer Dispersed-Liquid Crystal Displays with Low Driving Voltage

Polymer Dispersed-Liquid Crystal Displays with Low Driving Voltage

Polymer Dispersed-Liquid Crystal Displays with Low Driving Voltage

Polymer Dispersed-Liquid Crystal Displays with Low Driving Voltage

Mitigation of image blurring for performance enhancement in transparent displays based on polymer-dispersed liquid crystal

In this paper, we propose an effective real-time image enhancing technology for transparent displays based on polymer-dispersed liquid crystal (PDLC). The image enhancing technology consists of both global and local enhancement functions. It not only removes the affected haze but also sharpens the edge regions for transparent PDLC displays. This technology can improve the image quality such as contrast, brightness, color saturation, and gamma correction for transparent PDLC displays. The experimental results indicated that our proposed method can effectively enhance the visibility and remove the affected haze in the transparent PDLC display.

2D/3D switchable displays through PDLC reverse mode parallax barrier

ABSTRACTIn this paper, we present a new type of parallax barrier, for switchable 2D/3D display vision, obtained by using a Reverse Mode Polymer Dispersed Liquid Crystal display (RV-PDLC). The parallax barrier was prepared by sandwiching the RV-PDLC film between two ITO conductive glass supports. Strips of ITO were removed from one of the supports, in order to alternate conductive to not conductive strips. In this way the RV-PDLC films could be electrically switched in a parallax barrier able to turn a 2D image in a 3D one. The RV-PDLC barrier was obtained in tree steps: (1) a nematic diacrylate monomer (NDM) was dissolved in a nematic liquid crystal (NLC) in the presence of a small quantity of radical polymerisation initiator; (2) the mixture was homeotropically aligned between the glass conductive supports, previously treated with an aligning chemical; (3) the liquid crystal monomer was polymerised by UV curing. A 2D/3D switchable device was finally obtained by coupling the parallax barrier with a 2D tablet display.

Advances in the display quality of dye-doped polymer-dispersed liquid crystal films by addition of disc-shaped multidirectional light-control film

Typically, the addition of a dye is considered to increase the contrast ratio (CR) of a polymer-dispersed liquid crystal (PDLC) display; however, with the addition of a small amount of dye, the contrast ratio (CR) unexpectedly decreased as compare to the CR of a normal white PDLC display, attributed to various reasons. In this study, an additional multidirectional light scattering polymer film is developed over a conventional dye-doped polymer-dispersed liquid crystal (DPDLC) film to enhance the CR. For this, a disc-shape (DS) pattern on PN393 film is coated. This structure is believed to enhance the scattering properties of DPDLC displays via multiple-directional scattering nature of DS pattern film. Fabrications of such devices are simple and have advantageous of its low-cost production. This optimal designed disc-shaped light-scattering (DSS) film resulted in the enhancement of the CR of the DPDLCs.

Highly conductive PEDOT:PSS film by incorporating secondary doping and post-treatment for ITO-free polymer dispersed liquid crystal display

ABSTRACTIn this paper, highly conductive poly(3,4-ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) thin films realized by incorporating secondary doping technique with post-treatment process is demonstrated. The conductivity of the PEDOT:PSS film enhanced greatly from 0.6 S/cm to 736 S/cm after 1.25% of p-toluenesulfonic acid solution was doped into the PEDOT:PSS dispersion. The post-treatment using dimethyl sulfoxide further improved the conductivity to 1549 S/cm. We found that the electro-optical properties of the polymer dispersed liquid crystal (PDLC) cells fabricated by the highly conductive PEDOT:PSS films were comparable to those constructed by ITO. This work reveals that highly conductive PEDOT:PSS film is a suitable material for manufacturing ITO-free liquid crystal devices.

Carbon Nanotube Macroelectronics for Active Matrix Polymer-Dispersed Liquid Crystal Displays

Active matrix liquid crystal display (AMLCD) is the most widely used display technology nowadays. Transparent display is one of the emerging technologies to provide people with more features such as displaying images on transparent substrates and simultaneously enabling people to see the scenery behind the panel. Polymer-dispersed liquid crystal (PDLC) is a possible active matrix transparent display technology due to its high transparency, good visibility, and low power consumption. Carbon nanotubes (CNTs) with excellent mobility, high transparency, and room-temperature processing compatibility are ideal materials for the driver circuit of the PDLC display. Here, we report the monolithic integration of CNT thin-film transistor driver circuit with PDLC pixels. We studied the transmission properties of the PDLC pixels and characterized the performance of CNT thin-film transistors. Furthermore, we successfully demonstrated active matrix seven-segment PDLC displays using CNT driver transistors. Our achievements open up opportunities for future nanotube-based, flexible thin-film transparent display electronics.

Techniques to Reduce Driving Energy of 1-Pixel Displays

We propose a pair of techniques to lower the energy consumed by driving 1-pixel liquid-crystal displays (LCDs). The first one employs multiple capacitors while the other divides the LCD into two to lower the drive voltage. Simulations show that large capacitance values and many capacitors reduce the energy consumed, and stacking two thin low voltage LCDs maximizes the effect by decreasing the overhead consumed by the microcontroller. Actual polymer-dispersed LCDs (PDLCDs) are tested to confirm that the techniques work as effectively as the simulations imply. The results show that the overall energy consumption of large PDLCDs is reduced more than 70% using multiple capacitors, and the combination of the two techniques successfully reduces the driving energy even for small LCDs. While the polarity reversal of the proposed technique does incur some delay, it was confirmed by a flicker test that the technique does not degrade image quality.

40.3: 4.8 inch QVGA Color Reflective AM‐PDLCD Driven by Printed OFETs

AbstractWe have developed polymer‐dispersed liquid crystal display (PDLCD) driven by ink‐jet printed OFET. Novel pixel design and cell architecture are proposed to obtain enough current to drive PDLCD and high aperture ratio. 4.8 inch color reflective display has been fabricated successfully with the reflectivity of 18 % and contrast ratio of 4:1.

Synthesis and properties of highly birefringent liquid crystalline materials: 2,5-bis(5-alkyl-2-butadinylthiophene-yl) styrene monomers

In order to obtain liquid crystals with high birefringence (Δn), a series of new liquid crystals monomers incorporating styrene, a 2,5-disubstituted thiophene ring and diacetylenes, which were highly conjugated along the molecular long axis, were synthesized. Their physical properties were evaluated. As expected, they exhibited high Δn values of 0.4–0.7 and a low melting point and were of potential use for polymer-dispersed liquid crystal displays (PDLCDs), cholesteric displays and laser beam steering applications.

Effect of Alignment Layer on Electro-Optic Properties of Polymer-Dispersed Liquid Crystal Displays

The electro-optic properties of polymer-dispersed liquid crystal (PDLC) cell having parallel alignment layers were examined and compared to the control cell without any pre-treatment. Although the liquid crystal droplets of the treated PDLC was observed to be much smaller than that of the control cell, the contrast ratio of both cells are quite similar over a wide temperature range. The control cell performed better in terms of response time and operating voltage. The retardation characteristics of the cells showed sharp contrast, which may bring about inconsistent consequence in determining their electro-optic properties.

56.4: Cholesteric PDLC Displays with Low Driving Voltage

We present a new single-substrate approach for cholesteric polymer-dispersed liquid crystal (PDLC) displays that provides a uniform monolayer of liquid crystal domains over large areas. The monolayer structure, in combination with the most recent commercially available liquid crystal mixtures, enables the creation of flexible display devices with very low driving voltage.

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

Abstract—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.

Improvement of the Switching Parameters of Addressable Bistable Type PDLC Displays with Dual Frequency Driven Liquid Crystal

AbstractImprovement of switching parameters is reported of bistable polymer dispersed liquid crystal (PDLC) with dual frequency driven liquid crystal in an acrylate polymer matrix. Low frequency voltage pulses result in the transparent state while high frequency pulses return to the opaque state; which is a time useful for practical applications, e.g. still pictures. Both states are maintained even when removing the applied voltage. Repeatedly applying of high frequency voltage pulses recover the device to the initial scattering state with high reproducibility. Polymer content and surface treatment of substrates drastically affect the PDLC droplet formation and also bistability as a result.