Abstract— New smart‐card applications like purse cards, etc. require an integrated display which allows the card‐holder to read information which is stored on the IC of the card. On the other hand, the integration of a display into a plastic card requires some very specific features like flexibility and pressure stability, low‐voltage CMOS‐addressing, memory capability, and, of course, a reflective mode since no backlight is available. In this paper, two bistable reflective LCD solutions using ferroelectric and cholesteric LCs are discussed and very promising prototype results are presented. Pressure and bending tests as well as contrast measurements are compared in order to show the potential of meeting the requirements for use in smart cards.
Optical Computing and Signal Processing is a growing field of scientific research and now more and more entering into industrial applications. Therefore, fast switching Spatial Light Modulators (SLMs) are needed for displaying and filtering processed information.In this paper we present a transmissive Ferroelectric Liquid Crystal Display (FLCD) with high performance which will be operated as an SLM in an optical pattern recognition system using incoherent optical spatial frequency analysis (OSFA). The layout and the manufacturing process of the display have been designed especially for the requirements of SLMs in optical systems. The matrix is consisting of a square matrix of 512 columns by 512 rows with a spatial resolution of 5O8dpi. An additional black aperture diagphragm of 1mm is introduced around the active area in the switching plane of the PLC.The display is passively addressed with a multiplex driving scheme using the intrinsic bistability of the PLC. Each pixel of the display represents a switchable half wave plate, resulting in binary amplitude or phase modulated pictures dependent on the polarizer settings. Using an PLC with a high spontaneous polarization and a high pretilt at the substrate surfaces, we obtain excellent contrast ratios of 100: 1 and a very high switching speed based on a row address time of less than 7.5.tsec allowing frame rates up to 500 pictures/sec.
Abstract— The optical performance of surface‐stabilized cholesteric liquid‐crystal displays (SCT‐LCDs) has been optimized by using obliquely sputtered SiO2 as the alignment layer. A comparison with polyimides used up to now showed an improvement in the contrast ratio by a factor of 2 for glass displays. A second advantage of this material is the absence of high temperatures during the manufacturing process. Therefore, it is possible to use obliquely sputtered SiO2 for the preparation of plastic display prototypes. We have realized a 6‐in. VGA display with approximately 130 dpi. This is the largest cholesteric display with the highest resolution fabricated on plastic substrates to date.
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