A simple optical system is described which allows for the variation of the viewing angle of transmissive-type LCDs. It is well suited for automatic teller machines (ATMs) to switch between a wide viewing angle state which is defined by the used LCD and a restricted viewing angle for privacy, where a contrast of 30 at normal viewing direction decreases to a value of less than 0.3 at an angle of 30°.
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.
A 2" matrix of 12288 light sensors was realized on a plastic substrate by low temperature thin film technology. In comparison to a glass realization the sensor matrix has a reduced weight, is unbreakable and flexible. Each sensor cell contains a photoconductor as a resistive sensor and a TFT for reading out the resistor values line by line. By using amorphous silicon for both the channel of the TFT and the photoconductor it is possible to fabricate the sensor matrix with a low number of masks. As gate insulator amorphous silicon nitride is used. The above mentioned films were deposited in a PECVD reactor in the same vacuum at 180°C which is suitable for PES-foils. The mismatch of the thermal expansion coefficients of the thin films and the plastic substrates causes peeling of the films and cracks. The remedy is the use of sputtered adhesion layers for the metallization and PECVD layers. To qualify the different adhesion layers a tape test method was used. Cracks were avoided by reducing the internal stress. For this reason a new layout was designed in which all PECVD layers are patterned in islands providing a minimum of internal stress. The TFTs show an ON/OFF ratio of 6 decades and a mobility of 0.3 cm2/Vs. The change of the a-Si:H conductivity under illumination is 6 nS/W/cm2. This value allows for a dynamic range of the sensor matrix of 60 dB. The new flexible sensor offers a wide variety of applications like an electronic eye with a round view for the observation of work pieces and traffic signs.
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