29.1: Polarizer‐Free Reflective LCD Combined with Ultra Low‐Power Driving Technology

Abstract

We have developed a novel reflective LCD without polarizers, which is sure to provide excellent visibility (reflectance = 50%, CR = 10:1). Moreover, we have also achieved extremely low power consumption of 10 microwatts to introduce low frequency driving (less than 1Hz) without flicker and image sticking. These characteristics were realized to combine pixel memory circuit and new PNLC material. IntroductionInformation displays have widely prevailed among our daily life. That means, it demands much effort to broaden application fields of electronic displays and to develop the information society further, and therefore the importance of the low power consumption is arising more than ever. Since the power consumption of the conventional electronic displays is still high enough to limit their usage pattern or usage environment. In particular, such functions as the reflective display, the low frame rate drive and the ability to memorize images are quite effective to realize the display consuming low electric power. The display images can be memorized by using the electrophoretic display [1] or the cholesteric liquid crystal display [2], but those displays have required relatively high driving voltages and slow responses.From these viewpoints, the combination of the reflective type of liquid crystal display (RLCD) [3] and the drive scheme such as the low frame rate drive [4] or the pixel-memory circuit [5-6] should be a promising candidate. Since the power consumption of an LCD module generally depends on driving frequency, the lower the frame rate gets, the lower power the module consumes. And the pixel-memory circuit technology enables the module to have any images memorized at the pixels with the data driver suspended.An RLCD using polymer network liquid crystals (PNLC) [7] is the display system to control transmission or scattering of incoming light ray without polarizers. Its remarkable features are high light utilization efficiency due to polarizer-free system and low level of dependence on viewing angle. And a PNLC is one of solutions to realize an energy saving, paper-like display.In the meantime, a PNLC has had a couple of challenges for TFT drive, which are high driving voltage, slow response and low voltage holding ratio. However recent progress of the PNLC materials enables TFT drive of a PNLC by improving the properties above [8].Our objective is to develop an ultra low-power-consumption RLCD with excellent visibilities by using the one-bit pixel memory technology and the PNLC. PrincipleOur newly developed display is composed of the PNLC layer formed between a transparent electrode and mirror reflective pixel electrodes, and the one-bit pixel memory circuits embedded in the pixel area under the reflective mirror electrodes. Pixel Memory TechnologyThe system block diagram of our newly developed pixel memory display is shown in Figure 1. The interface of this display is very simple, because only 5 input lines are necessary for operating this display including power supplies. Timing generator with a 3-line se...

Low-Power Driving Technique for 1-Pixel Display Using an External Capacitor

“…The benefits of the PDLC are not limited to 1-pixel displays, multi-pixel displays are also possible. For example, the segmented PLNC (polymer network liquid crystal) display consumes ultra low power [20], and a directviewing display with PDLCs can provide high optical efficiency [21]. Normal LCDs are also used as 1-pixel displays rather than PDLCD, but mainly as a shutter.…”

“…Lowering the driving frequency was examined in [20], applying lower voltage at the cost of lower contrast, or the use of memory display are candidates for successfully reducing the power consumption, however they are not suitable for some applications such as the active tag [1] or shutters. The charge sharing technique would work effectively for 1-pixel displays.…”

“…Lowering the driving frequency is a major approach to reducing the power consumption [10], [11], [20] and combining with it the proposed technique would offer higher efficiency. In such LCD-based applications with infrequent polarity reversal, longer time for polarity reversal, may impact the LCD service quality by creating flicker.…”

Principal Component Analysis of Multi-Pigment Scenario in Full-Color Electrophoretic Display

“…E-Paper is a direct view electronic display that is either bi-stable or nearly bi-stable with the benefit of extremely low power consumption. Generally, there are several scenarios to implement the bi-stability (or nearly bi-stability), including electrophoretic [1]- [7], electrofluidic [8], [9], bi-stable liquid crystal display (LCD) [10], [11], electrowetting [12], [13] and other emerging approaches [14]. Despite jeopardized by the great success of emissive displays and their accompanying PC devices, e-Paper still has potential to leverage its strongest advantages which emissive counterparts are hard to achieve, such as superior energy saving, fine contrast under sunlight, continuous roll-to-roll manufacturing, flexible format, or even paper-like reading comfort.…”

Oxide-Thin-Film-Transistor-Based Ferroelectric Memory Array

“…However, the conventional pixel memories are composed of normal thin-film transistors (TFTs) rather than ferroelectric transistors. Therefore, they occupy a large area to constitute a static memory like an SRAM [1]- [5]. We report a simple pixel memory structure composed of three In-Ga-Zn-O (IGZO) TFTs as shown in Fig.…”