Abstract    
Low  cost and power consumption with superb quality are the key success of all  modern electronics. Cost reduction is very efficient when it is achieved by the  concepts design review and reducing of IC components. The decrease of power  consumption always results in lower heat dissipation and is welcomed by  portable applications. Recently proposed by us Optical Re-Writable LC Display1  does not require electronic schemes with power supply and conductive layers inside  the display device. Our design has great mechanical stability and excellent optical  characteristics that makes it perfect for plastic cards application.    
Our display is  a single LC cell with usual alignment material on one substrate and special photosensitive  azo-dye aligning material (SD-1) on the other  substrate. SD1 type materials can reversibly change their in-plane orientation.  Thus switching between dark and bright levels with intermediate analog grey is  performed by the change of LC orientation on the alignment layer by a polarized  light. It corresponds to the change of twist angle between 0º and 90º degrees.    
Image writing  consists of two steps: erasing the previous image and new image writing though  a mask. The mask can be a regular TN display with any information displayed on  it. The image can be registered on ORW LCD by UV light passed through the TN  display.    
Our recent  experiments have shown that sensitivity of the material is high enough that  365nm UV-LED can be used as a light source for image rewriting. Transmission-Dose  curve is presented on the figure1. Besides UV LED has widen emitting peak that  prevent from undesired interference that take place with 365nm line of Hg-lamp.  The interference causes of required writing dose in case of non-uniform  cell-gap or samples cell-gap deviation.    
A combination  of TN display and UV LED array makes possible to create a portable, handheld  device for fast image writing that operates on batteries and has wireless  connection with the computer. It widens possible applications of our ORW LC  display that can be rewritable labels & signs, as well as plastic cards.  The resolution is not fixed and contrast can be very high, over 100:1. So barcodes  can not only be written and rewritten, but also read by the present reading  machines.    
The support from ITF grant ITS/111/03 is gratefully acknowledged.

¹ A. Murauski, V.Chigrinov, Li Xihua, H.S. Kwok, Optically rewriteable LC display with a high contrast and long life time, IDW/AD '05, LCTp1-10L, pp.131-132 (2005)

Figure1. ORW LC cell transmission dependence on exposed dose during image writing and erasing. Single 365nm 1mW UV-LED from LDP LLC, USA was used.