Amorphous twisted nematic–liquid-crystal displays fabricated by nonrubbing showing wide and uniform viewing-angle characteristics accompanying excellent voltage holding ratios

Abstract

A new twisted-nematic (TN)–liquid-crystal display (LCD) device has been prepared without rubbing, which is called the no-rubbing (NR) technique. The device is shown to exhibit wide and uniform viewing-angle characteristics without showing a contrast inversion in the vertical direction of the cell. This characteristic is achieved in particular by filling chiral-molecular-doped nematic LCs (NLCs) in the isotropic phase into a cell. The substrate surfaces of the cells are either bare indium-tin-oxide films or those coated with polymer materials such as polyimide. These films are optically and structurally isotropic in a quasi-macroscopic scale (say, 100×100 μm2). In particular, the polymer films are capable of stabilizing and homogenizing the distribution of the NLC directors at the surfaces. The TN-LCDs fabricated by the NR technique, called amorphous TN-LCDs, are also featured by the excellent voltage holding ratio which is necessary to achieve good active matrix driving, and, furthermore, the device exhibits a very small viewing angular dependence in the electro-optic (EO) characteristics, which provides a significant benefit for achieving a good gray-scale operation. This rubbing-free technology may contribute not only to the significant improvement of the EO performance of TN-LCDs but also to the simplification of the production process and in turn to the reduction of the production cost.