Diamond-like carbon film applied as an alignment layer for LCDs

Diamond-like carbon (DLC) films have been applied as an alignment layer for liquid crystal displays (LCDs). There are two ways to align the DLC films for liquid crystals (LC). One way is to use non-contact alignment processes on DLC such as ion beam (IB) or linearly polarized UV light. The other way is to use novel self-aligned DLC film. No alignment processes such as rubbing or atomic beam bombardment or UV irradiation on DLC are necessary. In other words, DLC itself is self-aligned for LC as deposited. In the first section, a DLC film which uses an additional alignment process is described, and in the second section a self-aligned DLC film without an alignment process is described. The DLC films which are used with non-contact alignment processes were deposited by chemical vapor deposition (CVD) or reactive DC magnetron sputtering on indium tin oxide (ITO) transparent electrodes on a glass. For this alignment process the DLC films can contain no or some hydrogen. The mechanism of liquid crystals (LC) alignment appears to be due to the C=C Π bonds (sp2) orientation of the alignment layer. Therefore, with the non-contact alignment processes Π bonds on the DLC surface remain more in one direction. As a result, LC aligns on the DLC films. Many amorphous, transparent, and electrically insulated films were investigated, and DLC films were the first to be optimized. On the other hand, the self-aligned DLC films were deposited without hydrogen by using a DC magnetron in-line sputtering system only. The LC director alignment direction seems to be parallel to the substrate movement that is parallel to the magnetic field of the cathode and perpendicular to the plasma track line on the target during the in-line sputtering. The alignment mechanism of this DLC film seems to be related to the DLC crystalline structure that relates to the anisotropy of the Π bonds orientation.